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LTC1174 LTC1174-3.3/LTC1174-5 High Efficiency Step-Down and Inverting DC/DC Converter
FEATURES

DESCRIPTIO
High Efficiency: Up to 94% Peak Inductor Current Independent of Inductor Value Short-Circuit Protection Optimized for 5V to - 5V Applications Wide VIN Range: 4V to 18.5V Low Dropout Operation Low-Battery Detector Pin Selectable Current Limit Internal 0.9 Power Switch: VIN = 9V Only Four External Components Required 130A Standby Current Active Low Micropower Shutdown
The LTC(R)1174 is a simple current mode DC/DC converter ideally suited for 9V to 5V, 5V to 3.3V or 5V to - 5V operation. With an internal 0.9 switch (at a supply voltage of 9V), the LTC1174 requires only four external components to construct a complete high efficiency DC/DC converter. Under a no load condition the LTC1174 draws only 130A. In shutdown, it draws a mere 1A making this converter ideal for current sensitive applications. In dropout, the internal P-channel MOSFET switch is turned on continuously allowing the user to maximize the life of the battery source. The maximum inductor current of the LTC1174 family is pin selectable to either 340mA or 600mA, optimizing efficiency for a wide range of applications. Operation up to 200kHz permits the use of small surface mount inductors and capacitors. For applications requiring higher output current or ultrahigh efficiency, see the LTC1148 data sheet.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
APPLICATIO S

Distributed Power Systems Step-Down Converters Inverting Converters Memory Backup Supply Portable Instruments Battery-Powered Equipment
TYPICAL APPLICATIO
VIN 9V 3 2 7
High Efficiency Step-Down Converter
100
LTC1174-5 Efficiency
6 VIN LBIN LBOUT IPGM LTC1174-5 GND 4 SHUTDOWN VOUT SW
+
8 1 5 100H
EFFICIENCY (%)
15F* 25V x3
95 VIN = 6V 90 85 80 75 L = 100H VOUT = 5V IPGM = 0V 1 10 LOAD CURRENT (mA) 100 200
1174 TA02
5V 175mA
+
1N5818
100F** 10V
1174 TA01
* (3) AVX TPSD156K025 ** AVX TPSD107K010 COILTRONICS CTX100-4
70
U
VIN = 9V
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1
LTC1174 LTC1174-3.3/LTC1174-5
ABSOLUTE
AXI U
RATI GS
(Voltage Referred to GND Pin) Input Supply Voltage (Pin 6) LTC1174 ........................................... - 0.3V to 13.5V LTC1174HV ...................................... - 0.3V to 18.5V Switch Current (Pin 5) .............................................. 1A Switch Voltage (Pin 5) LTC1174 ................................................. VIN - 13.5V LTC1174HV ............................................ VIN - 18.5V
PACKAGE/ORDER I FOR ATIO
TOP VIEW VOUT (VFB*) 1 LBOUT 2 LBIN 3 GND 4 N8 PACKAGE 8-LEAD PDIP * ADJUSTABLE OUTPUT VERSION TJMAX = 125C, JA = 110C/W 8 7 6 5 SHUTDOWN IPGM VIN SW
ORDER PART NUMBER LTC1174CN8 LTC1174CN8-3.3 LTC1174CN8-5 LTC1174IN8 LTC1174HVCN8 LTC1174HVCN8-3.3 LTC1174HVCN8-5
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL IFB VFB VOUT VOUT PARAMETER Feedback Current Feedback Voltage Regulated Output Voltage Output Voltage Line Regulation
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
CONDITIONS LTC1174/LTC1174HV LTC1174/LTC1174HV LTC1174-3.3/LTC1174HV-3.3 LTC1174-5/LTC1174V-5 VIN = 6V to 12V, ILOAD = 100mA, IPGM = VIN (Note 3) MIN

2
U
U
W
WW
U
W
(Note 1)
Operating Temperature Range LTC1174CX ............................................ 0C to 70C LTC1174IX ........................................ - 40C to 85C Junction Temperature (Note 2) ............................ 125C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
TOP VIEW VOUT (VFB*) 1 LBOUT 2 LBIN 3 GND 4 8 7 6 5 SHUTDOWN IPGM VIN SW
S8 PACKAGE 8-LEAD PLASTIC SO * ADJUSTABLE OUTPUT VERSION
TJMAX = 125C, JA = 150C/W
ORDER PART NUMBER LTC1174CS8 LTC1174CS8-3.3 LTC1174CS8-5 LTC1174IS8 LTC1174HVCS8 LTC1174HVCS8-3.3 LTC1174HVCS8-5 LTC1174HVIS8
S8 PART MARKING 1174 117433 117450 1174I 1174H 1174H3 1174H5 1174HI
TYP 1.25 3.30 5.00 10
1.20 3.14 4.75
MAX 1 1.30 3.46 5.25 70
UNITS A V V V mV
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LTC1174 LTC1174-3.3/LTC1174-5
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER Output Voltage Load Regulation
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
CONDITIONS LTC1174-3.3 (Note 3) 20mA < ILOAD < 175mA, IPGM = 0V 20mA < ILOAD < 400mA, IPGM = VIN LTC1174-5 (Note 3) 20mA < ILOAD < 175mA, IPGM = 0V 20mA < ILOAD < 400mA, IPGM = VIN Active Mode LTC1174: 4V < VIN < 12V, IPGM = 0V LTC1174HV: 4V < VIN < 16V, IPGM = 0V Sleep Mode LTC1174: 4V < VIN < 12V LTC1174HV: 4V < VIN < 16V SHUTDOWN (Note 4) LTC1174: VSHUTDOWN = 0V, 4V < VIN < 12V LTC1174HV: VSHUTDOWN = 0V, 4V < VIN < 16V MIN TYP -5 -45 -5 -50 450 450 130 130 1 2 1.25 1.0 0.6 7.5 0.54 0.27 1.2 0.8 15 0.60 0.34 0.75 0.90 4 MAX -70 -70 -70 -70 600 600 180 180 10 25 1.4 0.5 1.5 1.5 30 0.83 0.53 1.30 1.55 5 0.75 0.5 2.0 0.5 UNITS mV mV mV mV A A A A A A V A mA mA mV A A s V V A A A
IQ
Input DC Supply Current (Note 4)
VLBTRIP ILBIN ILBOUT VHYST IPEAK RON tOFF VIH VIL IIH IIL
Low-Battery Trip Point Current into Pin 3 Current Sunk by Pin 2 Comparator Hysteresis Current Limit ON Resistance of Switch Switch Off-Time (Note 6) SHUTDOWN Pin High SHUTDOWN Pin Low SHUTDOWN Pin Input Current SHUTDOWN Pin Input Current
LTC1174: VLBOUT = 0.4V LTC1174HV: VLBOUT = 0.4V LTC1174/LTC1174HV IPGM = VIN, VOUT = 0V IPGM = 0V, VOUT = 0V LTC1174 LTC1174HV VOUT at Regulated Value Minimum Voltage at Pin 8 for Device to Be Active Maximum Voltage at Pin 8 for Device to Be in Shutdown LTC1174: VSHUTDOWN = 12V LTC1174HV: VSHUTDOWN = 16V 0 VSHUTDOWN 0.8V

3 1.2
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at - 40C TA 85C. LTC1174I and LTC1174HVI Only.
SYMBOL PARAMETER VFB Feedback Voltage ILBOUT Current Sunk by Pin 2 IPEAK Current Limit CONDITIONS LTC1174I/LTC1174HVI VLBOUT = 0.4V (LTC1174I) VLBOUT = 0.4V (LTC1174HVI) IPGM = VIN, VOUT = 0V (LTC1174I) IPGM = 0V, VOUT = 0V (LTC1174I) IPGM = VIN, VOUT = 0V (LTC1174HVI) IPGM = 0V, VOUT = 0V (LTC1174HVI) VOUT at Regulated Value (LTC1174I) VOUT at Regulated Value (LTC1174HVI) LTC1174I/LTC1174HVI

MIN 1.18 0.75 0.50 0.54 0.5 2.0 1.8
tOFF RON
Switch Off-Time (Note 6) Switch On Resistance
TYP 1.25 1.2 0.8 0.60 0.34 0.60 0.34 4 4 0.9
MAX 1.31 2.0 1.6 0.84 0.86 6.0 6.2 1.7
UNITS V mA mA A A A A s s
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.
Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formulas: LTC1174CN8, LTC1174CN8-3.3, LTC1174CN8-5: TJ = TA + (PD x 110C/W) LTC1174CS8, LTC1174CS8-3.3, LTC1174CS8-5: TJ = TA + (PD x 150C/W)
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LTC1174 LTC1174-3.3/LTC1174-5
ELECTRICAL CHARACTERISTICS
Note 3: Guaranteed by design. Note 4: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. Note 5: Current into Pin 6 only, measured without electrolytic input capacitor. Note 6: The off-time is wafer-sort trimmed.
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Load Current
100 95 100 95
VIN = 6V
EFFICIENCY (%)
EFFICIENCY (%)
VIN = 9V 85 80 75 70
EFFICIENCY (%)
90
L = 50H VOUT = 5V IPGM = 0V COIL = CTX50-4 1 10 LOAD CURRENT (mA) 100 200
1174 G01
Efficiency vs Load Current
100 VIN = 5V 100
90
EFFICIENCY (%)
EFFICIENCY (%)
80
80
VIN = 9V
EFFICIENCY (%)
VIN = 9V
70 L = 50H VOUT = 3.3V IPGM = 0V COIL = CTX50-4 1 10 100 LOAD CURRENT (mA) 300
1174 G04
60
50
4
UW
Efficiency vs Load Current
100 95 VIN = 6V VIN = 9V 85 80 75 70 1 10 100 LOAD CURRENT (mA) 400
1174 G02
Efficiency vs Load Current
VIN = 6V 90 VIN = 9V 85 80 75 70 1 10 100 LOAD CURRENT (mA) 500
1174 G03
90
L = 50H VOUT = 5V IPGM = VIN COIL = CTX50-4
L = 100H VOUT = 5V IPGM = VIN COIL = CTX100-4
Efficiency vs Load Current
100 VIN = 5V
Efficiency vs Load Current
90
90
VIN = 5V
80
VIN = 9V
70 L = 50H VOUT = 3.3V IPGM = VIN COIL = CTX50-4 1 10 100 LOAD CURRENT (mA) 500
1174 G05
70 L = 100H VOUT = 3.3V IPGM = VIN COIL = CTX100-4 1 10 100 LOAD CURRENT (mA) 500
1174 G06
60
60
50
50
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LTC1174 LTC1174-3.3/LTC1174-5 TYPICAL PERFOR A CE CHARACTERISTICS
Line Regulation
6 4 2 ILOAD = 100mA IPGM = 0V
LEAKAGE CURRENT (nA)
EFFICIENCY (%)
0
VOUT (mV)
-2 -4 -6 -8 -10 -12 -14 0 2 8 6 4 10 INPUT VOLTAGE (V) 12 14
Efficiency vs Input Voltage
95 94 93 92 91 90 0.2 89 5 6 7 8 9 10 11 12 INPUT VOLTAGE (V) 13 14 0 ILOAD = 100mA IPGM = 0V VOUT = 5V L = 100H COIL = CTX100-4 1.8 1.6
SUPPLY CURRENT (A)
SUPPLY CURRENT (A)
EFFICIENCY (%)
ILOAD = 300mA IPGM = VIN
Operating Frequency vs VIN - VOUT
2.0 VOUT = 5V
NORMALIZED FREQUENCY
1.7 1.6 1.5
1.5
RDS(ON) ()
OFF-TIME (s)
TA = 25C 1.0 TA = 70C 0.5
0 0 1 5 7 3 6 2 4 (VIN - VOUT) VOLTAGE (V) 8 9
UW
1174 G07 1174 G10
Switch Leakage Current vs Temperature
180 160 140 120 100 80 60 40 20 0 0 20 60 40 TEMPERATURE (C) 80 100
1174 G08
Efficiency vs Input Voltage
95 94 93 92 91 90 89 88 87 5 6 7 9 10 11 12 8 INPUT VOLTAGE (V) 13 14 VOUT = 5V IPGM = 0V ILOAD = 75mA CORE = CTX (Kool M(R)) L = 50H L = 100H
VIN = 13.5V
1174 G09
Supply Current in Shutdown
500 SHUTDOWN = 0V TA = 25C CURRENT INTO PIN 6 ONLY 450 400 350 300 250 200 150 100 50 0 0 2 4 6 8 10 INPUT VOLTAGE (V) 12 14
DC Supply Current
ACTIVE MODE IPGM = 0V IPGM = VIN
1.4 1.2 1.0 0.8 0.6 0.4
SLEEP MODE
TA = 25C 0 2 8 6 4 10 INPUT VOLTAGE (V) 12 14
1174 G11
1174 G12
Switch Resistance vs Input Voltage
50
TA = 25C
Off-Time vs Output Voltage
40
1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 4 6 8 10 12 14 16 INPUT VOLTAGE (V) 18 20 LTC1174 LTC1174HV
30
20 LTC1174-5 LTC1174HV-5 10 LTC1174-3.3 LTC1174HV-3.3 0 1 3 4 2 OUTPUT VOLTAGE (V) 5
1174 G15
0
1174 G13
1174 G14
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LTC1174 LTC1174-3.3/LTC1174-5
PI FU CTIO S
VOUT (VFB) (Pin 1): For the LTC1174, this pin connects to the main voltage comparator's input. On the LTC1174-3.3 and LTC1174-5 this pin goes to an internal resistive divider which sets the output voltage. LBOUT (Pin 2): Open Drain of an N-Channel Pull-Down. This pin will sink current when Pin 3 (LBIN) goes below 1.25V. During shutdown the state of this pin is indeterminate. LBIN (Pin 3): The "-" Input of the Low-Battery Voltage Comparator. The "+" input is connected to a reference voltage of 1.25V. GND (Pin 4): Ground Pin. SW(Pin5): Drain of the P-Channel MOSFET Switch. Cathode of Schottky diode must be closely connected to this pin. VIN (Pin 6): Input Supply Voltage. It must be decoupled close to ground Pin 4. IPGM (Pin 7): Selects the Current Limit of the P-Channel Switch. With IPGM = VIN, the current trip point is 600mA and with IPGM = 0V, the current trip value is reduced to 340mA. SHUTDOWN (Pin 8): Pulling this pin to ground keeps the internal switch off and puts the LTC1174 in micropower shutdown.
FU CTIO AL DIAGRA
+
VTH2 A5 SLEEP A2
-
-
A4 gmVFB CT RESET Q VOUT (VFB)
+
SET VTH1 LBIN
LBOUT 2
-
A3
+
GND 4
6
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(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)
VIN 6
VLIM1
VLIM2 IPGM RSENSE 0.1
+ -
7
x
R1* 3
1
5 SW
-
A1 1.25V REFERENCE SHUTDOWN 8
VFB 31.5k
+
* R1 = 51k FOR LTC1174-3.3 R1 = 93.5k FOR LTC1174-5
1174 BD
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LTC1174 LTC1174-3.3/LTC1174-5
OPERATIO
The LTC1174 uses a constant off-time architecture to switch its internal P-channel power MOSFET. The off-time is set by an internal timing capacitor and the operating frequency is a function of VIN. The output voltage is set by an internal resistive divider (LTC1174-3.3 and LTC1174-5) or an external divider returned to VFB Pin 1 (LTC1174). A voltage comparator A1 compares the divided output voltage to a reference voltage of 1.25V. To optimize efficiency, the LTC1174 automatically switches between continuous and Burst Mode(R) operation. The voltage comparator is the primary control element when the device is in Burst Mode operation, while the current comparator controls the output voltage in continuous mode. During the switch"ON" time, switch current flows through the 0.1 sense resistor. When this current reaches the threshold of the current comparator A2, its output signal will change state, setting the flip-flop and turning the switch off. The timing capacitor, CT, begins to discharge until its voltage goes below VTH1. Comparator A4 will then trip, which resets the flip-flop and causes the switch to turn on again. Also, the timing capacitor is recharged. The inductor current will again ramp up until the current comparator A2 trips. The cycle then repeats. When the load is relatively light, the LTC1174 automatically goes into Burst Mode operation. The current mode loop is interrupted when the output voltage reaches the desired regulated value. The hysteretic voltage comparator A1 trips when VOUT is above the desired output voltage, shutting off the switch and causing the timing capacitor to discharge. This capacitor discharges past VTH1 until its voltage drops below VTH2. Comparator A5 then trips and a sleep signal is generated.
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(Refer to Functional Diagram)
In sleep mode, the LTC1174 is in standby and the load current is supplied by the output capacitor. All unused circuitry is shut off, reducing quiescent current from 0.45mA to 0.13mA. When the output capacitor discharges by the amount of the hysteresis of the comparator A1, the P-channel switch turns on again and the process repeats itself. Operating Frequency and Inductor Since the LTC1174 utilizes a constant off-time architecture, its operating frequency is dependent on the value of VIN. The frequency of operation can be expressed as:
f= 1 VIN - VOUT t OFF VIN + VD
(Hz)
where tOFF = 4s and VD is the voltage drop across the diode. Note that the operating frequency is a function of the input and ouput voltage. Although the size of the inductor does not affect the frequency, it does affect the ripple current. The peak-to-peak ripple current is given by: + VD V IRIPPLE = 4 * 10 -6 OUT L
( A P- P)
By choosing a smaller inductor, a low ESR output filter capacitor has to be used (see CIN and COUT). Moreover, core loss will also increase (see Inductor Core Selection section) due to higher ripple current.
Burst Mode is a registered trademark of Linear Technology Corporation.
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LTC1174 LTC1174-3.3/LTC1174-5
APPLICATIO S I FOR ATIO
Inductor Core Selection
With the value of L selected, the type of inductor must be chosen. Basically there are two kinds of losses in an inductor, core and copper Core losses are dependent on the peak-to-peak ripple current and the core material. However it is independent of the physical size of the core. By increasing the inductance the inductor's peak-to-peak ripple current will decrease, therefore reducing core loss. Utilizing low core loss material, such as molypermalloy or Kool M will allow users to concentrate on reducing copper loss and preventing saturation. Figure 1 shows the effect of different core material on the efficiency of the LTC1174. The CTX core is Kool M and the CTXP core is powdered iron (material 52). Although higher inductance reduces core loss, it increases copper loss as it requires more windings. When space is not
100 CTX100-4 CTX100-4P 80
90
EFFICIENCY (%)
70
60
VIN = 5V VOUT = 3.3V IPGM = VIN 1 10 100 LOAD CURRENT (mA) 500
50
100 CTX50-4 CTX50-4P 80
90
EFFICIENCY (%)
70
60
VIN = 5V VOUT = 3.3V IPGM = VIN 1 10 100 LOAD CURRENT (mA) 500
1174 F01
50
Figure 1. Efficiency Using Different Types of Inductor Core Material
8
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a premium larger gauge wire can be used to reduce the wire resistance. This also prevents excessive heat dissipation. CIN In continuous mode the source current of the P-channel MOSFET is a square wave of duty cycle VOUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The CIN RMS current is given by:
IRMS IOUT VOUT ( VIN - VOUT ) VIN
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[
]1/2 (A ) RMS
This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT/2. This simple worst case is commonly used for design because even significant deviations do not offer much relief. Note that ripple current directly affects capacitor's lifetime. DO NOT UNDERSPECIFY THIS COMPONENT. An additional 0.1F ceramic capacitor is also required on VIN for high frequency decoupling. COUT To avoid overheating, the output capacitor must be sized to handle the ripple current generated by the inductor. The worst case RMS ripple current in the output capacitor is given by:
IRMS
IPEAK ( A RMS) 2 = 170 mA or 300mA
Although the output voltage ripple is determined by the hysteresis of the voltage comparator, ESR of the output capacitor is also a concern. Too high of an ESR will create a higher ripple output voltage and at the same time cause the LTC1174 to sleep less often. This will affect the efficiency of the LTC1174. For a given technology, ESR is a direct function of the volume of the capacitor. Several small-sized capacitors can also be paralleled to obtain the same ESR as one large can. Manufacturers such as Nichicon, Chemicon and Sprague should be considered for high performance capacitors. The OS-CON semiconductor dielectric capacitor available from Sanyo has the lowest ESR for its size, at a higher price.
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LTC1174 LTC1174-3.3/LTC1174-5
APPLICATIO S I FOR ATIO
Catch Diode Selection
The catch diode carries load current during the off-time. The average diode current is therefore dependent on the P-channel switch duty cycle. At high input voltages the diode conducts most of the time. As VIN approaches VOUT the diode conducts only a small fraction of the time. The most stressful condition for the diode is when the output is short-circuited. Under this condition the diode must safely handle IPEAK at close to 100% duty cycle. A fast switching diode must also be used to optimize efficiency. Schottky diodes are a good choice for low forward drop and fast switching times. Most LTC1174 circuits will be well served by either a 1N5818, a MBRS140T3 or a MBR0520L Schottky diode. Short-Circuit Protection The LTC1174 is protected from output short by its internal current limit. Depending on the condition of IPGM pin, the limit is either set to 340mA or 600mA. In addition, the offtime of the switch is increased to allow the inductor's current to decay far enough to prevent any current build-up (see Figure 2).
IPGM = VIN
IPGM = 0
GND
1174 F02
L = 100H VIN = 13.5V
20s/DIV
Figure 2. Inductor's Current with Output Shorted
Low-Battery Detector The low-battery indicator senses the input voltage through an external resistive divider. This divided voltage connects to the "-" input of a voltage comparator (Pin 3) which is
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compared with a 1.25V reference voltage. With the current going into Pin 3 being negligible, the following expression is used for setting the trip limit: R4 VLBTRIP = 1.251 + R3 When the LTC1174 is shut down, the low-battery detector is inactive.
VIN R4 3 R3 LTC1174
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- +
1.25V REFERENCE
1174 F03
Figure 3. Low-Battery Comparator
LTC1174 Adjustable/Low Noise Applications The LTC1174 develops a 1.25V reference voltage between the feedback (Pin 1) terminal and ground (see Figure 4). By selecting resistor R1, a constant current is caused to flow through R1 and R2 to set the overall output voltage. The regulated output voltage is determined by: R2 VOUT = 1.25 1 + R1 For most applications, a 30k resistor is suggested for R1. To prevent stray pickup, a 100pF capacitor is suggested across R1 located close to the LTC1174. Alternatively, a capacitor across R2 can be used to increase the switching frequency for low noise operation. Inverting Applications The LTC1174 can easily be set up for a negative output voltage. If - 5V is desired, the LTC1174-5 is ideal for this application as it requires the least components. Figure 5 shows the schematic for this application. Note that the
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LTC1174 LTC1174-3.3/LTC1174-5
APPLICATIO S I FOR ATIO
6.8nF** LTC1174 VFB 1 100pF* R1 R2
* ADJUSTABLE APPLICATIONS ** LOW NOISE APPLICATIONS
1174 F04
Figure 4. LTC1174 Adjustable Configuration
INPUT VOLTAGE 4V TO 12V
3 2 7
6 VIN LBIN LBOUT IPGM LTC1174HV-5 GND 4 SHUTDOWN VOUT SW
+
0.1F 8 1 5 50H** MBRS140T3
47F* 16V x2
+
47F* 16V x2
* AVX TPSD476K016 ** COILTRONICS CTX50-4
Figure 5. Positive-to-Negative 5V Converter
output voltage is now taken off the GND pin. Therefore, the maximum input voltage is now determined by the difference between the absolute maximum voltage rating and the output voltage. A maximum of 12V is specified in Figure 5, giving the circuit a 1.5V of headroom for VIN. Note that the circuit can operate from a minimum of 4V, making it ideal for a 4 NiCad cell application. For a higher output current circuit, please refer to the Typical Applications section. Absolute Maximum Ratings and Latchup Prevention The absolute maximum ratings specify that SW (Pin 5) can never exceed VIN (Pin 6) by more than 0.3V. Normally this situation should never occur. It could, however, if the output is held up while the supply is pulled down. A condition where this could potentially occur is when a battery is supplying power to an LTC1174/LTC1174-3.3/
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VOUT
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LTC1174-5 regulator and also to one or more loads in parallel with the the regulator's VIN. If the battery is disconnected while the LTC1174/LTC1174-3.3/LTC1174-5 regulator is supplying a light load and one of the parallel circuits is a heavy load, the input capacitor of the LTC1174/ LTC1174-3.3/LTC1174-5 regulator could be pulled down faster than the output capacitor, causing the absolute maximum ratings to be exceeded. The result is often a latchup which can be destructive if VIN is reapplied. Battery disconnect is possible as a result of mechanical stress, bad battery contacts or use of a lithium-ion battery with a built-in internal disconnect. The user needs to assess his/her application to determine whether this situation could occur. If so, additional protection is necessary. Prevention against latchup can be accomplished by simply connecting a Schottky diode across the SW and VIN pins as shown in Figure 6. The diode will normally be reverse biased unless VIN is pulled below VOUT at which time the diode will clamp the (VOUT - VIN) potential to less than the 0.6V required for latchup. Note that a low leakage Schottky should be used to minimize the effect on no-load supply current. Schottky diodes such as MBR0530, BAS85 and BAT84 work well. Another more serious effect of the protection diode leakage is that at no load with nothing to provide a sink for this leakage current, the output voltage can potentially float above the maximum allowable tolerance. To prevent this from occuring, a resistor must be connected between VOUT and ground with a value low enough to sink the maximum possible leakage current.
LATCHUP PROTECTION SCHOTTKY
VOUT -5V 45mA
1174 F05
VIN
SW
VOUT
LTC1174 LTC1174-3.3 LTC1174-5
+
1174 F06
Figure 6. Preventing Absolute Maximum Ratings from Being Exceeded
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LTC1174 LTC1174-3.3/LTC1174-5
APPLICATIO S I FOR ATIO
Board Layout Checklist
When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC1174. These items are also illustrated graphically in the layout diagram in Figure 7. Check the following in your layout: 1. Is the Schottky catch diode closely connected between ground (Pin 4) and switch (Pin 5)? 2. Is the "+" plate of CIN closely connected to VIN (Pin 6)? This capacitor provides the AC current to the internal P-channel MOSFET. 3. Is the 0.1F VIN decoupling capacitor closely conected between VIN (Pin 6) and ground (Pin 4)? This capacitor carries the high frequency peak currents. 4. Is the SHUTDOWN (Pin 8) actively pulled to VIN during normal operation? The SHUTDOWN pin is high impedance and must not be allowed to float. 5. Is the IPGM (Pin 7) pulled either to VIN or ground? The IPGM pin is high impedance and must not be allowed to float.
INDUCTOR CURRENT
OUTPUT DIVIDER REQUIRED WITH ADJUSTABLE VERSION ONLY
R2
Figure 7. LTC1174 Layout Diagram (See Board Layout Checklist)
+
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DESIGN EXAMPLE As a design example, assume VIN = 9V (nominal), VOUT = 5V, and IOUT = 350mA maximum. The LTC1174-5 is used for this application, with IPGM (Pin 7) connected to VIN. The minmum value of L is determined by assuming the LTC1174-5 is operating in continuous mode.
IPEAK AVG CURRENT = IOUT I +I = PEAK V IV 2 = 350mA TIME
1174 F08
W
UU
Figure 8. Continuous Inductor Current
With IOUT = 350mA and IPEAK = 0.6A (IPGM = VIN), IV = 0.1A.The peak-to-peak ripple inductor current, IRIPPLE, is 0.5A and is also equal to: + VD V IRIPPLE = 4 * 10 -6 OUT L
( A P- P)
R1
1 VOUT (VFB) 2 LBOUT 3 LBIN 4
SHUTDOWN IPGM LTC1174 VIN
8 7 6 0.1F 5 D VIN CIN
+
GND
SW
BOLD LINES INDICATE HIGH CURRENT PATH
COUT
L VOUT
1174 F07
1174fe
11
LTC1174 LTC1174-3.3/LTC1174-5
APPLICATIO S I FOR ATIO
Solving for L in the above equation and with VD = 0.6V, L = 44.8H. The next higher standard value of L is 50H (example: Coiltronics CTX50-4). The operating frequency, neglecting voltage across diode VD is: V f 2.5 * 105 1 - OUT VIN = 111kHz With the value of L determined, the requirements for CIN and COUT are calculated. For CIN, its RMS current rating should be at least: IRMS = IOUT VOUT ( VIN - VOUT ) VIN
[
]
1/ 2
( A RMS)
= 174mA For COUT, the RMS current rating should be at least:
IRMS
IPEAK ( A RMS) 2 = 300mA
12
U
Now allow VIN to drop to 6V. At this minimum input voltage the operating frequency will decrease. The new frequency is 42kHz.
Table 1. Inductor Manufacturers
MANUFACTURER Coilcraft 1102 Silver Lake Road Cary, IL 60013 (708) 639-2361 Coiltronics Inc. 6000 Park of Commerce Blvd. Boca Raton, FL 33487 (407) 241-7876 Gowanda Electronics Corporation 1 Industrial Place Gowanda, NY 14070 (716) 532-2234 Sumida Electric Co. Ltd. 637 E. Golf Road, Suite 209 Arlington Heights, IL 60005 (708) 956-0666/7 PART NUMBER DT3316 Series Econo-Pac Octa-Pac GA10 Series CD 54 Series CD 75 Series
W
UU
Table 2. Capacitor Manufacturers
MANUFACTURER AVX Corporation P.O. Box 887 Myrtle Beach, SC 29578 (803) 448-9411 Nichicon America Corporation 927 East State Parkway Schaberg, IL 60173 (708) 843-7500 Sanyo Video Components 2001 Sanyo Avenue San Diego, CA 92173 (619) 661-6385 Attn: Sales Dept. PART NUMBER TPS Series TAJ Series
PL Series
OS-CON Series
1174fe
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
6V to 5V Step-Down Regulator with Low-Battery Detection
* LOW-BATTERY INDICATOR IS SET TO TRIP AT VIN = 5.5V ** AVX TPSD476K016 D1 = MBRS140T3 (SURFACE MOUNT) 1N5818 L1 SELECTION MANUFACTURER PART NO. TYPE COILTRONICS CTX100-4 SURFACE MOUNT SUMIDA CD75-101 SURFACE MOUNT GOWANDA GA10-103K THROUGH HOLE
INPUT VOLTAGE 4V TO 12.5V 7 3
* AVX TPSD226K025 ** AVX TPSD476K016 COILTRONICS CTX50-4
U
INPUT VOLTAGE 6V 6 VIN 7 2 IPGM SHUTDOWN
4.7k *LOWBATTERY INDICATOR 162k
0.1F 8
+
47F** 16V x2
1 LBOUT VOUT LTC1174-5 3 5 SW LBIN GND 4 D1
47.5k
L1 100H
+
1174 TA03
VOUT 5V 47F** 365mA 16V x2
High Efficiency 3.3V Regulator
6 VIN IPGM LBIN SHUTDOWN
+
8
22F* 25V x3
0.1F
1 VOUT LTC1174-3.3 2 5 LBOUT SW GND 4
50H
1N5818
+
1174 TA04
VOUT 3.3V 47F** 425mA 16V x2
1174fe
13
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
Low Noise 3V Regulator
INPUT VOLTAGE 4V TO 12.5V 7 3 2
* AVX TPSD226K025 ** AVX TPSD105K010 COILTRONICS CTX50-4
* LOW-BATTERY INDICATOR VIN(V) IOUT MAX(mA) IS SET TO TRIP AT VIN = 4.4V 4 110 ** AVX TPSD106K035 6 140 *** AVX TPSD105K010 170 D1 = MBRS130LT3 (SURFACE MOUNT) 8 10 200 1N5818 12.5 235 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA PART NO. CTX50-3 DT3316-473 CD54-470 GA10-472K TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
14
U
6 VIN IPGM LBIN LTC1174 LBOUT GND 4 SW SHUTDOWN VFB
+
8 1 5
22F* 25V x3
0.1F
50H
6.8nF 42k
VOUT 3V 450mA
+
1N5818
100F** 10V x2
1174 TA05
30k
Positive-to-Negative (- 5V) Converter
INPUT VOLTAGE 4V TO 12.5V 6 VIN 7 2 IPGM SHUTDOWN
+
0.1F 8
4.7K *LOWBATTERY INDICATOR 280k
10F** 35V x2
1 LBOUT VOUT LTC1174HV-5 3 5 SW LBIN GND 4 D1
43k
L1 50H
+
100F*** 10V
1174 TA06
VOUT -5V
1174fe
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
Positive-to-Negative (- 3.3V) Converter
* LOW-BATTERY INDICATOR IS SET TO TRIP AT VIN = 4.4V VIN(V) IOUT MAX(mA) ** AVX TPSD336K020 175 4 *** AVX TPSD105K010 205 D1 = MBRS140T3 (SURFACE MOUNT) 5 230 6 1N5818 255 7 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA PART NO. CTX50-3 DT3316-473 CD54-470 GA10-472K TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
* AVX TPSD336K020 D1 = MBRS140T3 (SURFACE MOUNT) 1N5818 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA PART NO. CTX50-3 DT3316-473 CD54-470 GA10-472K TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
U
INPUT VOLTAGE 4V TO 13.5V 6 VIN 7 2 IPGM SHUTDOWN
+
0.1F 8
4.7K *LOWBATTERY INDICATOR 220k
33F** 20V x2
1 LBOUT VOUT LTC1174HV-3.3 3 5 SW LBIN GND 4 D1
43k
L1 50H
+
100F*** 10V x2
1174 TA07
VOUT -3.3V 210mA
Negative Boost Converter
6 VIN 7 2 IPGM SHUTDOWN
8
310k
+
33F* 16V x2
1 LBOUT VOUT LTC1174-3.3 3 5 SW LBIN GND 4 D1 L1 50H 50k 0.1F
0.1F
+
33F* 20V x2
1174 TA08
VOUT -9V 175mA
INPUT VOLTAGE -5V
1174fe
15
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
9V to 5V Pre-Post Regulator
INPUT VOLTAGE 6V TO 12.5V * SANYO OS-CON ** AVX TPSD476K016 D1 = MBRS140T3 (SURFACE MOUNT) 1N5818 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA
PART NO. CTX50-3 DT3316-473 CD54-470 GA10-472K
TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
USE 1% METAL FILM RESISTORS
VIN(V) IOUT MAX(mA) 4 20 5 25 6 30 7 35 8 43 9 50 10 55 11 60 12 65 * AVX TAJE106K050 ** AVX TPSD476K016 D1 = MBRS140T3 (SURFACE MOUNT) 1N5818 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA PART NO. CTX100-3 DT3316-104 CD75-101 GA10-103K
INPUT VOLTAGE 4V TO 12.5V 6 3 7 2 VIN LBIN IPGM LTC1174 LBOUT GND 4 0.1F SW SHUTDOWN VFB 8 1 5 1N914 2N5210
1174 TA10
USE 1% METAL FILM RESISTORS
16
+
TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
U
3 2 7
6 VIN LBIN LBOUT LTC1174 IPGM GND 4 SW SHUTDOWN VFB
+
8 1 5 L1 50H D1
100F* 16V
0.1F
8
+
110k 47F** 16V, x2 100pF 0.1F 30.1k
VIN OUT LT(R)1121-5 5 SHUTDOWN GND 3
1
VOUT 5V 150mA
+
1F SOLID TANTALUM
1174 TA09
LCD Display Power Supply
56.2k
2N2222 50k
998k Si9435 D1 VOUT -24V 50mA AT 10F* VIN = 9V 50V x4
+
47F** 16V x2
0.1F L1 100H
1174fe
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
9V to 5V, - 5V Outputs
INPUT VOLTAGE 4V TO 12.5V * SANYO OS-CON ** WIMA MKS2 COILTRONICS CTX100-4 VIN(V) IOUT MAX(mA) 4 75 6 100 8 125 10 145 12 160 13 180
3 2 CTX100-4 4 1
L1B
L1A
* AVX TAJD226K035 ** WIMA MKS2 COILTRONICS CTX100-4 USE 1% METAL FILM RESISTORS VIN(V) IOUT MAX(mA) 4 20 5 25 6 35 7 45 8 50 9 55 10 62 11 67 12 73
7 3 2
U
6 VIN 7 3 IPGM SHUTDOWN
+
0.1F 8 0.1F
100F* 20V
1 VOUT LBIN LTC1174HV-5 2 5 LBOUT SW GND 4 MBRS140T3 L1B 100H
3.3F** L1A 100H MBRS140T3
VOUT 5V 135mA AT VIN = 9V
+
100F* 16V -VOUT -5V 135mA AT VIN = 9V
+
100F* 16V
1174 TA11
9V to 12V, - 12V Outputs
INPUT VOLTAGE 4V TO 12.5V
6 VIN IPGM LBIN LTC1174 LBOUT GND 4 1N914 SW SHUTDOWN VFB 8 1 5
0.1F
+
22F* 35V x3
L1B
3 2 CTX100-4 4 1
L1A
Si9430DY 4
3.3F** 1 L1A 2 100H + MBRS140T3 301k 34k
L1B 100H 3
22F* 35V x2
VOUT 12V 55mA AT VIN = 9V
+
MBRS140T3
22F* 35V x2
1174 TA12
-VOUT -12V 55mA AT VIN = 9V
1174fe
17
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO S
Automatic Current Selection
INPUT VOLTAGE 6V TO 12.5V 100k 2 7 3 100k
100F* 20V
+
* SANYO OS-CON CAPACITOR COILTRONICS CTX50-4
* SANYO OS-CON ** WIMA MKS2 COILTRONICS CTX100-4
L1B
3 2 CTX100-4 4 1
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6 VIN LBOUT IPGM LTC1174-5 LBIN GND 4 SW SHUTDOWN VOUT
TPO610L 0.1F
8 1 5 50H VOUT 5V 0mA TO 320mA
+
1N5818
100F* 16V
100k
36.5k
1174 TA13
Buck-Boost Converter
INPUT VOLTAGE 4V TO 12V
6 VIN 7 3 IPGM SHUTDOWN
0.1F 8
+
100F* 20V
1 VOUT LBIN LTC1174HV-5 2 5 LBOUT SW GND 4 L2A 100H 3 4
3.3F** 1 L1A 2 100H 1N5818
1174 TA14
VOUT 5V 160mA
L1A
+
100F* 16V
1174fe
LTC1174 LTC1174-3.3/LTC1174-5
PACKAGE DESCRIPTIO U
N8 Package 8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400* (10.160) MAX 8 7 6 5 .045 - .065 (1.143 - 1.651) .130 .005 (3.302 0.127) .255 .015* (6.477 0.381) .120 (3.048) .020 MIN (0.508) MIN .018 .003 (0.457 0.076) 1 2 3 4
N8 1002
.300 - .325 (7.620 - 8.255)
.008 - .015 (0.203 - 0.381)
.065 (1.651) TYP
(
+.035 .325 -.015 8.255 +0.889 -0.381
)
.100 (2.54) BSC
INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
NOTE: 1. DIMENSIONS ARE
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 - .197 (4.801 - 5.004) NOTE 3 8 7 6 5
.045 .005 .050 BSC
.245 MIN
.160 .005
.228 - .244 (5.791 - 6.197)
.150 - .157 (3.810 - 3.988) NOTE 3
.030 .005 TYP RECOMMENDED SOLDER PAD LAYOUT
.010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP
1
2
3
4
.053 - .069 (1.346 - 1.752)
.004 - .010 (0.101 - 0.254)
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
.014 - .019 (0.355 - 0.483) TYP
.050 (1.270) BSC
SO8 0303
1174fe
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LTC1174 LTC1174-3.3/LTC1174-5
TYPICAL APPLICATIO
* AVX TAJD226K020 ** AVX TAJD107K010 D1,D2 = MBRS140T3 (SURFACE MOUNT) 1N5818 L1 SELECTION MANUFACTURER COILTRONICS COILCRAFT SUMIDA GOWANDA PART NO. CTX50-2P DT3316-473 CD54-470 GA10-472K
VIN(V) IOUT MAX(mA) 8 320 9 325 10 330 11 335 12 335 TYPE SURFACE MOUNT SURFACE MOUNT SURFACE MOUNT THROUGH HOLE
RELATED PARTS
PART NUMBER LT 1074/LT1076 LTC1147 LTC1265 LT1375/LT1376 LTC1574 LT1611 LTC1701 LTC1707 LTC1877
(R)
DESCRIPTION Step-Down Switching Regulator High Efficiency Step-Down DC/DC Controller 1.2A High Efficiency Step-Down DC/DC Regulator 1.5A 500kHz Step-Down Switching Regulator High Efficiency Step-Down DC/DC Regulator Inverting 1.4MHz Switching Regulator in SOT-23 1MHz Step-Down DC/DC Converter in SOT-23 High Efficiency Synchronous Step-Down Regulator High Efficiency Synchronous Step-Down Regulator
20
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
Battery Charger
INPUT VOLTAGE 8V TO 12.5V 6 VIN 7 3 2 IPGM LBIN LTC1174 LBOUT GND 4 D1 33k
1174 TA15
+
0.1F 8 1 5 L1 50H 150k
22F* 20V x2
SHUTDOWN VFB SW
D2
VOUT TO 4 NiCAD BATTERY
+
100F** 10V
COMMENTS 100kHz, 5A (LT1074) or 2A (LT1076) Monolithic 8-Pin Controller Burst Mode Operation, Monolithic High Frequency Small Inductor LTC1174 with Internal Schottky Diode - 5V at 150mA from 5V Input, 1mVP-P Output Ripple, SOT-23 Package VIN = 2.5V to 5.5V, IQ = 135A, VOUT = 5V to 1.25V VIN = 2.85 to 8.5V, Selectable Burst Mode Operation, 600mA Output Current, SO-8 Package 600mA at VIN = 5V, 2.65V to 10V = VIN, IQ = 10A
1174fe LT 1006 REV E * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1994

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