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NCP1410 250 mA Sync-Rect PFM Step-Up DC-DC Converter with Low-Battery Detector
NCP1410 is a monolithic micropower high frequency Boost (step-up) voltage switching converter IC specially designed for battery operated hand-held electronic products up to 250 mA loading. It integrates Synchronous Rectifier for improving efficiency as well as eliminating the external Schottky Diode. High switching frequency (up to 600 kHz) allows low profile inductor and output capacitor being used. Low-Battery Detector, Logic-Controlled Shutdown and Cycle-by-Cycle Current Limit provide value-added features for various battery-operated applications. With all these functions ON, the device quiescent supply current is only 9.0 A typical. This device is available in space saving compact Micro8 package.
Features http://onsemi.com MARKING DIAGRAM
8 Micro8 DM SUFFIX CASE 846A 1 1 A1 AYW
8
* * * * * * * * * * * * * * * * * * *
High Efficiency up to 92% Very Low Device Quiescent Supply Current of 9.0 mA Typical Allows use of Small Size Inductor and Capacitor Built-in Synchronous Rectifier (PFET) Eliminates One External Schottky Diode High Switching Frequency (up to 600 kHz) Allows Use of Small Size Inductor and Capacitor High Accuracy Reference Output, 1.19 V 0.6% @ 25C, can supply more than 2.5 mA when VOUT 3.3 V 1.0 V Startup at No Load Guaranteed Output Voltage from 1.5 V to 5.5 V Adjustable Output Current up to 250 mA @ Vin = 2.5 V, Vout = 3.3 V Logic-Controlled Shutdown Open Drain Low-Battery Detector Output 1.0 A Cycle-by-Cycle Current Limit Low Profile and Minimum External Parts Compact Micro8 Package Personal Digital Assistant (PDA) Handheld Digital Audio Product Camcorders and Digital Still Camera Hand-held Instrument Conversion from One or Two NiMH or NiCd, or One Li-ion Cell to 3.3 V/5.0 V
A1 = Device Marking A = Assembly Location Y = Year W = Work Week
PIN CONNECTIONS
FB 1 LBI 2 LBO 3 REF 4 (Top View) 8 OUT 7 LX 6 GND 5 SHDN
ORDERING INFORMATION
Device NCP1410DMR2 Package Micro8 Shipping 4000 Tape & Reel
Typical Applications
(c) Semiconductor Components Industries, LLC, 2001
1
December, 2001 - Rev. 2
Publication Order Number: NCP1410/D
NCP1410
Input 1.0 V to VOUT 10 F 500 k 22 F
150 pF 200 k
360 k + FB VOUT NCP1410 LX GND SHDN 56 nF LBI LBO Output 1.5 V to 5.5 V IOUT typical up to 33 F 250 mA at 3.3 V Output and 2.5 V Input
Low Battery Sense Input Low Battery Open Drain Output Shutdown Open Drain Input
REF 150 nF
Figure 1. Typical Operating Circuit
MAXIMUM RATINGS (Note 1)
Rating Device Power Supply (Pin 8) Input/Output Pins Pin 1-5, Pin 7 Thermal Characteristics Micro8 Plastic Package Maximum Power Dissipation @ TA = 25C Thermal Resistance Junction to Air Operating Junction Temperature Range Operating Ambient Temperature Range Storage Temperature Range 1. This device series contains ESD protection and exceeds the following tests: Human Body Model (HBM) $2.0 kV per JEDEC standard: JESD22-A114. Machine Model Method (MM) $200 V per JEDEC standard: JESD22-A115. 2. The maximum package power dissipation limit must not be exceeded. TJ(max) * TA PD + RqJA 3. Latch-up Current Maximum Rating: $150 mA per JEDEC standard: JESD78. 4. Moisture Sensitivity Level: MSL 1 per IPC/JEDEC standard: J-STD-020A. Symbol VOUT VIO Value -0.3 to 6.0 -0.3 to 6.0 Unit V V
PD RJA TJ TA Tstg
520 240 -40 to +150 -40 to +85 -55 to +150
mW C/W C C C
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NCP1410
ELECTRICAL CHARACTERISTICS (VOUT = 3.3 V, TA = 25C for typical value, -40C TA 85C for min/max values
unless otherwise noted.) Characteristics Operating Voltage Output Voltage Range (Adjusted by external feedback) Reference Voltage (CREF = 150 nF, under no loading, TA = 25C) Reference Voltage (CREF = 150 nF, under no loading, -40C TA 85C) Reference Voltage Temperature Coefficient Reference Voltage Load Current (VOUT = 3.3 V, VREF = VREF_NL 1.5%, CREF = 1.0 mF) (Note 5) Reference Voltage Load Regulation (VOUT = 3.3 V, IREF = 0 to 100 mA, CREF = 1.0 mF) Reference Voltage Line Regulation (VOUT from 1.5 V to 5.5 V, CREF = 1.0 mF) FB, LBI Input Threshold (ILOAD = 0 mA) N-FET ON Resistance P-FET ON Resistance LX Switch Current Limit (NFET) Operating Current into OUT (VFB = 1.4 V, i.e. No switching, VOUT = 3.3 V) Shutdown Current into OUT (SHDN = GND) LX Switch MAX. ON-Time (VFB = 1.0 V, VOUT = 3.3 V) LX Switch MIN. OFF-Time (VFB = 1.0 V, VOUT = 3.3 V) FB Input Current LBI Input Current LBO Low Output Voltage (VLBI = 0, ISINK = 1.0 mA) SHDN Input Current SHDN Input Threshold, Low SHDN Input Threshold, High 5. Loading capability increases with VOUT. Symbol VIN VOUT VREF_NL VREF_NL_A TCVREF IREF VREF_LOAD VREF_LINE VFB, VLBI RDS(ON)-N RDS(ON)-P ILIM IQ ISD tON tOFF IFB ILBI VLBO_L ISHDN VSHDN_L VSHDN_H - - - 1.2 0.25 - - - - - 0.6 Min 1.0 VIN 1.183 1.178 - 2.5 - - 1.174 Typ - - 1.190 - 0.03 - 0.015 0.03 1.190 0.6 0.9 1.0 9.0 0.05 1.4 0.31 1.5 1.5 - 1.5 - - - 14 1.0 1.8 0.37 9.0 8.0 0.05 8.0 0.3 - Max 5.5 5.5 1.197 1.202 - - 1.0 1.0 1.200 Unit V V V V mV/C mA mV mV/V V W W A mA mA mS mS nA nA V nA V V
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NCP1410
PIN FUNCTION DESCRIPTIONS
Pin # 1 2 3 4 5 6 7 8 Symbol FB LBI LBO REF SHDN GND LX OUT Output Voltage Feedback Input. Low-Battery Detector Input. Open-Drain Low-Battery Detector Output. Output is LOW when VLBI is t1.178 V. LBO is high impedance during shutdown. 1.190 V Reference Voltage Output, bypass with 150 nF capacitor if this pin is not loaded, bypass with 1.0 mF if this pin is loaded up to 2.5 mA @ VOUT = 3.3 V. Shutdown Input. HIGH (u 0.6 V) = operating; LOW (t 0.3 V) = shutdown. Ground. N-Channel and P-Channel Power MOSFET Drain Connection. Power Output. OUT provides bootstrap power to the IC. Pin Description
Vbat
L Vbat 5 RSHDN SHDN CSHDN Chip Enable _ZCUR _PWGONCE PFM + - _CEN _PFM _SYNSW2ON 4 REF CREF Voltage Reference _VREFOK _SYNSWOFD _ILIM + - ILIM GND GND _MAINSWOFD CONTROL LOGIC _MAINSW2ON M1 VDD GND VDD SENSEFET 6 COUT RFB2 ZLC + - 7 + 20 mV M2 VDD LX 8 OUT CFB1 RFB1 VOUT
1 FB
+
RSENSE 3 GND
2 LBI
+ -
LBO
GND
Figure 2. Simplified Functional Diagram
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NCP1410
TYPICAL OPERATING CHARACTERISTICS
1.212 REFERENCE VOLTAGE, VREF/V 1.208 1.204 1.2 1.196 VIN = 3.0 V 1.192 1.188 1.0 REFERENCE VOLTAGE, VREF/V VOUT = 3.3 V L = 22 H CIN = 10 F COUT = 33 F CREF = 1.0 F TA = 25C 1.195 1.193 IREF = 0 mA 1.190 1.188 IREF = 2.5 mA 1.185 1.183 1.180 1.5 CREF = 1.0 mF TA = 25C 2.0 2.5 3.0 3.5 4.0 5.0 4.5 INPUT VOLTAGE AT OUT PIN, VOUT,/V 5.5
VIN = 2.2 V VIN = 1.8 V
10 100 OUTPUT CURRENT, ILOAD/mA
1000
Figure 3. Reference Voltage vs. Output Current
Figure 4. Reference Voltage vs. Input Voltage at OUT pin
SWITCH ON RESISTANCE, RDS(ON)/W 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 N-FET (M1) P-FET (M2)
1.194 REFERENCE VOLTAGE, VREF/V
1.192
1.190
1.188 VOUT = 3.3 V CREF = 150 nF IREF = 0 mA -20 0 20 40 60 80 100
1.186
1.184 -40
AMBIENT TEMPERATURE, TA/C
AMBIENT TEMPERATURE, TA/C
Figure 5. Reference Voltage vs. Temperature
Figure 6. Switch ON Resistance vs. Temperature
LX SWITCH MAXIMUM ON TIME, tON/mS
1.8 MINIMUM STARTUP BATTERY VOLTAGE, VBATT/V 1.7 1.6 1.5 1.4 1.3 1.2 -40
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0 20 40 60 80 100 120 Without Schottky Diode
With Schottky Diode (MBR0502)
-20
0
20
40
60
80
100
AMBIENT TEMPERATURE, TA/C
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 7. LX Switch Maximum ON Time vs. Temperature
Figure 8. Minimum Startup Battery Voltage vs. Loading Current
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NCP1410
TYPICAL OPERATING CHARACTERISTICS
100 L = 22 H EFFICIENCY (%) 100 L = 27 H L = 22 H 80
90 EFFICIENCY (%)
90 L = 15 H
80
L = 10 H
70 60 VIN = 1.8 V VOUT = 3.3 V CIN = 10 F COUT = 33 F 10 100 1000
70 60 VIN = 2.2 V VOUT = 5.0 V CIN = 10 F COUT = 33 F 10 100 1000
50 1.0
50 1.0
OUTPUT LOADING CURRENT, ILOAD/mA
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 9. Efficiency vs. Load Current
Figure 10. Efficiency vs. Load Current
100 L = 22 H 90 EFFICIENCY (%) EFFICIENCY (%)
100 L = 27 H 90 L = 22 H 80
80
L = 10 H
L = 15 H
70 60 VIN = 2.2 V VOUT = 3.3 V CIN = 10 F COUT = 33 F 10 100 1000
70 60 VIN = 3.0 V VOUT = 5.0 V CIN = 10 F COUT = 33 F 10 100 1000
50 1.0
50 1.0
OUTPUT LOADING CURRENT, ILOAD/mA
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 11. Efficiency vs. Load Current
Figure 12. Efficiency vs. Load Current
100 L = 22 H 90 EFFICIENCY (%) EFFICIENCY (%)
100
L = 27 H
90 L = 22 H 80
80
L = 10 H
L = 15 H
70 60 VIN = 3.0 V VOUT = 3.3 V CIN = 10 F COUT = 33 F 10 100 1000
70 60 VIN = 4.5 V VOUT = 5.0 V CIN = 10 F COUT = 33 F 10 100 1000
50 1.0
50 1.0
OUTPUT LOADING CURRENT, ILOAD/mA
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 13. Efficiency vs. Load Current
Figure 14. Efficiency vs. Load Current
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NCP1410
TYPICAL OPERATING CHARACTERISTICS
3 2 1 3.0 V 0 2.2 V -1 -2 -3 1.0 L = 22 mH VOUT = 3.3 V CIN = 10 F COUT = 33 F 10 VIN = 1.8 V OUTPUT VOLTAGE CHANGE (%) OUTPUT VOLTAGE CHANGE (%) 3 2 1 3.0 V 0 2.2 V -1 -2 -3 1.0 L = 15 mH VOUT = 3.3 V CIN = 10 F COUT = 33 F 10 VIN = 1.8 V
100
1000
100
1000
OUTPUT LOADING CURRENT, ILOAD/mA
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 15. Output Voltage Change vs. Load Current
200 RIPPLE VOLTAGE, VRIPPLE/mVp-p RIPPLE VOLTAGE, VRIPPLE/mVp-p 180 160 140 120 100 80 60 40 20 0 1.0 1.5 2.0 2.5 3.0 100 mA 200 mA VOUT = 3.3 V CIN = 10 F COUT = 33 F L = 22 mH 200 180 160 140 120 100 80 60 40 20 0 1.0
Figure 16. Output Voltage Change vs. Load Current
VOUT = 3.3 V CIN = 10 F COUT = 33 F L = 15 mH
200 mA
100 mA 1.5 2.0 2.5 3.0
BATTERY INPUT VOLTAGE, VBATT/V
BATTERY INPUT VOLTAGE, VBATT/V
Figure 17. Output Ripple Voltage vs. Battery Input Voltage
NO LOAD OPERATING CURRENT, IBATT/A 14 12 10 8.0 6.0 4.0 2.0 0 0 1.0 2.0 3.0 4.0 5.0 INPUT VOLTAGE AT OUT PIN, VOUT/V 6.0
Figure 18. Output Ripple Voltage vs. Battery Input Voltage
(VIN = 2.2 V, VOUT = 3.3 V, ILOAD = 100 mA; L = 22 H, COUT = 33 F)
Upper Trace: Output Voltage Waveform, 2.0 V/Division Lower Trace: Shutdown Pin Waveform, 1.0 V/Division
Figure 19. No Load Operating Current vs. Input Voltage at OUT Pin
Figure 20. Startup Transient Response
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NCP1410
TYPICAL OPERATING CHARACTERISTICS
(VIN = 2.2 V, VOUT = 3.3 V, ILOAD = 10 mA; L = 22 H, COUT = 33 F)
(VIN = 2.2 V, VOUT = 3.3 V, ILOAD = 10 mA; L = 22 H, COUT = 33 F)
Upper Trace: Voltage at LX pin, 2.0 V/Division MiddleTrace Otuput Voltage Ripple, 50 mV/Division Lower Trace: Inductor Current, IL, 100 mA/Division
Upper Trace: Voltage at LX pin, 2.0 V/Division MiddleTrace Otuput Voltage Ripple, 50 mV/Division Lower Trace: Inductor Current, IL, 100 mA/Division
Figure 21. Continuous Conduction Mode Switching Waveform
Figure 22. Discontinuous Conduction Mode Switching Waveform
(VIN = 1.8 V, to 3.0 V, L = 22 H, COUT = 33 F)
Upper Trace: Battery Voltage, VIN, 1.0 V/Division Lower Trace: Output Voltage Ripple, 100 mV/Division
(VOUT = 3.3 V, ILOAD = 10 mA to 100 mA; L = 22 H, COUT = 33 F)
Upper Trace: Output Voltage Ripple, 100 mV/Division Lower Trace: Load Current, ILOAD, 50 mA/Division
Figure 23. Line Transient Response for VOUT = 3.3 V
Figure 24. Load Transient Response for VIN = 1.8 V
(VOUT = 3.3 V, ILOAD = 10 mA to 100 mA; L = 22 H, COUT = 33 F)
(VOUT = 3.3 V, ILOAD = 10 mA to 100 mA; L = 22 H, COUT = 33 F)
Upper Trace: Output Voltage Ripple, 100 mV/Division Lower Trace: Load Current, ILOAD, 50 mA/Division
Upper Trace: Output Voltage Ripple, 100 mV/Division Lower Trace: Load Current, ILOAD, 50 mA/Division
Figure 25. Load Transient Response for VIN = 2.4 V
Figure 26. Load Transient Response for VIN = 3.3 V
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NCP1410
DETAILED OPERATION DESCRIPTIONS NCP1410 is a monolithic micropower high frequency step-up voltage switching converter IC specially designed for battery operated hand-held electronic products up to 250 mA loading. It integrates Synchronous Rectifier for improving efficiency as well as eliminating the external Schottky Diode. High switching frequency (up to 600 kHz) allows low profile inductor and output capacitor being used. Low-Battery Detector, Logic-Controlled Shutdown and Cycle-by-Cycle Current Limit provide value-added features for various battery-operated application. With all these functions ON, the quiescent supply current is only 9.0 A typical. This device is available in a compact Micro8 package.
PFM Regulation Scheme
From the simplified Functional Diagram (Figure 2), the output voltage is divided down and fed back to pin 1 (FB). This voltage goes to the non-inverting input of the PFM comparator whereas the comparator's inverting input is connected to REF. A switching cycle is initiated by the falling edge of the comparator, at the moment, the main switch (M1) is turned ON. After the maximum ON-time (typical 1.4 S) elapses or the current limit is reached, M1 is turned OFF, and the synchronous switch (M2) is turned ON. The M1 OFF time is not less than the minimum OFF-time (typical 0.31 S), this is to ensure energy transfer from the inductor to the output capacitor. If the regulator is operating at continuous conduction mode (CCM), M2 is turned OFF just before M1 is supposed to be ON again. If the regulator is operating at discontinuous conduction mode (DCM), which means the coil current will decrease to zero before the next cycle, M1 is turned OFF as the coil current is almost reaching zero. The comparator (ZLC) with fixed offset is dedicated to sense the voltage drop across M2 as it is conducting, when the voltage drop is below the offset, the ZLC comparator output goes HIGH, and M2 is turned OFF. Negative feedback of closed loop operation regulates voltage at pin 1 (FB) equal to the internal voltage reference (1.190 V).
Synchronous Rectification
When the main regulator is operating in CCM, as M2 is being turned OFF, and M1 is just turned ON with M2 not being completed OFF, the above mentioned situation will occur. So dead time is introduced to make sure M2 is completed OFF before M1 is being turned ON. When the regulator is operating in DCM, as coil current is dropped to zero, M2 is supposed to be OFF. Fail to do so, reverse current will flow from the output bulk capacitor through M2 and then the inductor to the battery input. It causes damage to the battery. So the ZLC comparator comes with fixed offset voltage to switch M2 OFF before any reverse current builds up. However, if M2 is switch OFF too early, large residue coil current flows through the body diode of M2 and increases conduction loss. Therefore, determination on the offset voltage is essential for optimum performance. With the implementation of synchronous rectification, efficiency can be as high as 92%. For single cell input voltage, use an external Schottky diode such as MBR0520 connected from pin 7 to pin 8 to ensure start-up.
Cycle-by-Cycle Current Limit
From Figure 2, SENSEFET is applied to sample the coil current as M1 is ON. With that sample current flowing through a sense resistor, sense-voltage is developed. Threshold detector (ILIM) detects whether the sense-voltage is higher than preset level. If it happens, detector output signifies the CONTROL LOGIC to switch OFF M1, and M1 can only be switched ON as next cycle starts after the minimum OFF-time (typical 0.31 S). With properly sizing of SENSEFET and sense resistor, the peak coil current limit is set at 1.0 A typically.
Voltage Reference
The voltage at REF is set typically at +1.190 V. It can output up to 2.5 mA with load regulation 1.5%, at VOUT equal to 3.3 V. If VOUT is increased, the REF load capability can also be increased. A bypass capacitor of 0.15 F is required for proper operation when REF is not loaded. If REF is loaded, 1.0 mF capacitor at REF is needed.
Shutdown
Synchronous Rectifier is used to replace Schottky Diode for eliminating the conduction loss contributed by forward voltage of the latter. Synchronous Rectifier is normally realized by powerFET with gate control circuitry which, however, involved relative complicated timing concerns. As main switch M1 is being turned OFF, if the synchronous switch M2 is just turned ON with M1 not being completed turned OFF, current will be shunt from the output bulk capacitor through M2 and M1 to ground. This power loss lowers overall efficiency. So a certain amount of dead time is introduced to make sure M1 is completely OFF before M2 is being turned ON.
The IC is shutdown when the voltage at pin 5 (SHDN) is pulled lower than 0.3 V. During shutdown, M1 and M2 are both switched OFF, however, the body diode of M2 allows current flow from battery to the output, the IC internal circuit will consume less than 0.05 A current typically. If the pin 5 voltage is pull higher than 0.6 V, for example, by a resistor connected to VIN, the IC is enabled, and the internal circuit will only consume 9.0 A current typically from the OUT pin. Refer to Figure 2, the product of RSHDN and CSHDN must be larger than (500 k * 56 nF, i.e. 28 msec). This is to provide reset pulse for startup as battery is plugged in.
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NCP1410
Low-Battery Detection Capacitors Selection
A comparator with 30 mV hysteresis is applied to perform the low-battery detection function. When pin 2 (LBI) is at a voltage, which can be defined by a resistor divider from the battery voltage, lower than the internal reference voltage, 1.190 V, the comparator output will cause a 50 Ohm low side switch to be turned ON. It will pull down the voltage at pin 3 (LBO) which has a hundreds kilo-Ohm of pull-high resistance. If the pin 2 voltage is higher than 1.190 V + 30 mV, the comparator output will cause the 50 Ohm low side switch to be turned OFF, pin 3 will become high impedance, and its voltage will be pulled high by the external resistor. APPLICATIONS INFORMATION
Output Voltage Setting
In all switching mode boost converter applications, both the input and output terminals sees pulsating voltage/current waveforms. The currents flowing into and out of the capacitors multiplying with the Equivalent Series Resistance (ESR) of the capacitor producing ripple voltage at the terminals. During the syn-rect switch off cycle, the charges stored in the output capacitor is used to sustain the output load current. Load current at this period and the ESR combined and reflected as ripple at the output terminals. For all cases, the lower the capacitor ESR, the lower the ripple voltage at output. As a general guide line, low ESR capacitors should be used. Ceramic capacitors have the lowest ESR, but low ESR tantalum capacitors can also be used as a cost effective substitute.
Optional Startup Schottky Diode for Low Battery Voltage
The output voltage of the converter is determined by the external feedback network comprised of RFB1 and RFB2 and the relationship is given by:
VOUT + 1.190 V R 1 ) FB1 RFB2
where RF2 and RF1 are the upper and lower feedback resistors respectively.
Low Battery Detect Level Setting
In general operation, no external Schottky diode is required, however, in case you are intended to operate the device close to 1 V level, a Schottky diode connected between the LX and OUT pins as shown in Figure 27 can help during startup of the converter. The effect of the additional Schottky was shown in Figure 8.
L MBR0502 VOUT
The Low Battery Detect Voltage of the converter is determined by the external divider network comprised of RLB1 and RLB2 and the relationship is given by:
VLB + 1.190 V R 1 ) LB1 RLB2
NCP1410
OUT LX COUT
where RLB1 and RLB2 are the upper and lower divider resistors respectively.
Inductor Selection
The NCP1410 is tested to produce optimum performance with a 22 H inductor at VIN = 3 V, VOUT = 3.3 V supplying output current up to 250 mA. For other input/output requirements, inductance in the range 10 H to 47 H can be used according to end application specifications. Selecting an inductor is a compromise between output current capability and tolerable output voltage ripple. Of course, the first thing we need to obey is to keep the peak inductor current below its saturation limit at maximum current and the ILIM of the device. In NCP1410, ILIM is set at 1 A. As a rule of thumb, low inductance values supply higher output current, but also increase the ripple at output and reducing efficiency, on the other hand, high inductance values can improve output ripple and efficiency, however it also limit the output current capability at the same time. One other parameter of the inductor is its DC resistance, this resistance can introduce unwanted power loss and hence reduce overall efficiency, the basic rule is selecting an inductor with lowest DC resistance within the board space limitation of the end application.
Figure 27. Schottky Device Between LX and OUT Pins PCB Layout Recommendations
Good PCB layout plays an important role in switching mode power conversion. Careful PCB layout can help to minimize ground bounce, EMI noise and unwanted feedback that can affect the performance of the converter. Hints in the following paragraphs, can be used as guidelines in most situations.
Grounding
Star-ground connection should be used to connect the output power return ground, the input power return ground and the device power ground together at one point. All high current running paths must be thick enough for current flowing through and producing insignificant voltage drop along the path. Feedback signal path must be separated with the main current path and sensing directly at the anode of the output capacitor.
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NCP1410
Components Placement Feedback Network
Power components, i.e. input capacitor, inductor and output capacitor, must be placed as close together as possible. All connecting traces must be short, direct and thick. High current flowing and switching paths must be kept away from the feedback (FB, pin 1) terminal to avoid unwanted injection of noise into the feedback path.
Feedback of the output voltage must be a separate trace detached from the power path. External feedback network must be placed very close to the feedback (FB, pin 1) pin and sensing the output voltage directly at the anode of the output capacitor.
TYPICAL APPLICATION CIRCUIT
VIN = 1.8 V to 3.0 V VBATT RLB1 225 K
RFB1 355 K
CFB 150 pF
L
22 H
VOUT = 3.3 V/250 mA max. VOUT
+ CIN 10 F/ 10 V
1 FB 2 LBI 3 LBO NCP1410
VOUT 8 LX 7 GND 6 SHDN 5 CSHDN 56 nF GND RSHDN 560 K + COUT 33 F/ 10 V
GND
RLB2 330 K
RFB2 200 K
4 REF CREF 150 nF
Figure 28. Typical Application Schematic for 2 Alkaline Cells Supply
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NCP1410
GENERAL DESIGN PROCEDURES Switching mode converter design is considered as black magic to most engineers, some complicate empirical formulae are available for reference usage. Those formulae are derived form the assumption that the key components, i.e. power inductor and capacitors are available with no tolerance. Practically, its not true, the result is not a matter of how accurate the equations you are using to calculate the component values, the outcome is still somehow away from the optimum point. In below a simple method base on the most basic first order equations to estimate the inductor and capacitor values for NCP1410 operate in Continuous Conduction Mode is introduced. The component value set can be used as a starting point to fine tune the circuit operation. By all means, detail bench testing is needed to get the best performance out of the circuit.
Design Parameters:
Determine the Steady State Duty Ratio, D for typical VIN, operation will be optimized around this point:
VOUT 1 + VIN 1*D D+1* VIN + 1 * 2.4 V + 0.273 3.3 V VOUT
Determine the average inductor current, ILAVG at maximum IOUT:
I 250 mA ILAVG + OUT + + 344 mA 1 * 0.273 1*D
Determine the peak inductor ripple current, IRIPPLE-P and calculate the inductor value: Assume IRIPPLE-P is 20% of ILAVG, the inductance of the power inductor can be calculated as in below: IRIPPLE-P = 0.20 x 344 mA = 68.8 mA
L+ VIN tON 2.4 V 0.4 mS + + 24.4 mH 2(68.8 mA) 2 IRIPPLE * P
VIN = 1.8 V to 3.0 V, Typical 2.4 V VOUT = 3.3 V IOUT = 200 mA (250 mA max) VLB = 2.0 V VOUT-RIPPLE = 40 mVP-P at IOUT = 250 mA Calculate the feedback network: Select RFB2 = 200 K
RFB1 + RFB2 RFB1 + 200 K VOUT *1 VREF 3.3 V * 1 + 355 K 1.19 V
Standard value of 22 H is selected for initial trial. Determine the output voltage ripple, VOUT-RIPPLE and calculate the output capacitor value: VOUT-RIPPLE = 40 mVP-P at IOUT = 250 mA
COUT u IOUT tON VOUT-RIPPLE * IOUT ESRCOUT 250 mA 0.4 mS + 23.33 mF 40 mV * 250 mA 0.1 W
where tON = 1.4 S and ESRCOUT = 0.1 ,
COUT u
Calculate the Low Battery Detect divider: VLB = 2.0 V Select RLB2 = 330 K
RLB1 + RLB2 RLB1 + 330 K VLB *1 VREF 2.0 V * 1 + 225 K 1.19 V
From above calculation, you need at least 23.33 mF in order to achieve the specified ripple level at conditions stated. Practically, a one level larger capacitor will be used to accommodate factors not take into account in the calculation, therefore a capacitor value of 33 mF is selected.
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NCP1410
PACKAGE DIMENSIONS
Micro8 DM SUFFIX CASE 846A-02 ISSUE E
-A-
K
-B-
NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.15 (0.006) PER SIDE. 4. DIMENSION B DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. INTERLEAD FLASH OR PROTRUSION SHALL NOT EXCEED 0.25 (0.010) PER SIDE. DIM A B C D G H J K L MILLIMETERS MIN MAX 2.90 3.10 2.90 3.10 --1.10 0.25 0.40 0.65 BSC 0.05 0.15 0.13 0.23 4.75 5.05 0.40 0.70 INCHES MIN MAX 0.114 0.122 0.114 0.122 --0.043 0.010 0.016 0.026 BSC 0.002 0.006 0.005 0.009 0.187 0.199 0.016 0.028
PIN 1 ID
G D 8 PL 0.08 (0.003)
M
TB
S
A
S
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0.038 (0.0015) H
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NCP1410
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NCP1410
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NCP1410
Micro8 is a trademark of International Rectifier SENSEFET is a trademark of Semiconductor Components Industries, LLC.
ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer.
PUBLICATION ORDERING INFORMATION
Literature Fulfillment: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303-675-2175 or 800-344-3860 Toll Free USA/Canada Fax: 303-675-2176 or 800-344-3867 Toll Free USA/Canada Email: ONlit@hibbertco.com N. American Technical Support: 800-282-9855 Toll Free USA/Canada JAPAN: ON Semiconductor, Japan Customer Focus Center 4-32-1 Nishi-Gotanda, Shinagawa-ku, Tokyo, Japan 141-0031 Phone: 81-3-5740-2700 Email: r14525@onsemi.com ON Semiconductor Website: http://onsemi.com For additional information, please contact your local Sales Representative.
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NCP1410//D

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