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LTC1696 Overvoltage Protection Controller
FEATURES
s s s
DESCRIPTIO
s s s s
2% Overvoltage Threshold Accuracy Low Profile (1mm) ThinSOTTM Package Gate Drive for SCR Crowbar or External N-Channel Disconnect MOSFET Monitors Two Output Voltages Senses Output Voltages from 0.8V to 24V Wide Supply Range: 2.7V to 27V Multifunction TIMER/RESET Pin
The LTC(R)1696 is a standalone power supply overvoltage monitor and protection device designed to protect a power supply load in the event of an overvoltage fault. It monitors two adjustable output voltages. If an overvoltage condition is detected, the output drives either an external SCR crowbar or turns off external back-to-back N-channel MOSFETs, thereby, disconnecting the input voltage from the power supply. Pin 6 offers three functions. By connecting a capacitor to this pin, the internal glitch filter time delay can be programmed. Without the capacitor, the default time delay is determined by an internal capacitor. This pin also serves as a reset input to clear the internal latch after an overvoltage fault condition. By pulling it high, the OUT pin is activated if the FB1 and FB2 voltages remain below the trip threshold. The LTC1696 is available in the low profile (1mm) ThinSOT package.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation.
APPLICATIO S
s s s s
Telecommunication Systems Computer Systems Industrial Control Systems Notebook Computers
TYPICAL APPLICATIO
SCR Crowbar Overvoltage Response
VCC 12V POWER SUPPLY VOUT2 5V VOUT1 3.3V R4 232k 1% C1 1nF Q1 2N7002 RESET
IOUT 20mA/DIV FB1 0.5V/DIV
R2 137k 1% R1 44.2k 1%
1
FB1
TIMER/ 6 RESET LTC1696
TIMER/RESET 2V/DIV
2
GND
FB2
5 R3 44.2k 1%
3 SCR 2N6507 C2 0.1F
VCC
OUT
4
1696 TA01
U
C1 = 1nF 100s/DIV
1696 TA02
U
U
1
LTC1696
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW FB1 1 GND 2 VCC 3 TIMER/ RESET 5 FB2 6 4 OUT
Supply Voltage (VCC) ............................................... 28V Input Voltage FB1, FB2 ............................................... - 0.3V to 17V TIMER/RESET .......................................- 0.3V to 17V Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC1696ES6 S6 PART MARKING LTLT
S6 PACKAGE 6-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 256C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VCC IVCC VFB IFB VFBHST VLKO PARAMETER Supply Voltage Range Standby Supply Current Active Supply Current FB1, FB2 Feedback Threshold FB1, FB2 Input Current FB1, FB2 Feedback Hysteresis VCC Undervoltage Lockout Low-to-High Transition High-to-Low Transition VCC Undervoltage Lockout Hysteresis TIMER/RESET Reset Low Threshold TIMER/RESET Timer High Threshold TIMER/RESET External Trigger High Threshold TIMER/RESET External Trigger High Current TIMER/RESET Timer Current
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. 2.7V VCC 27V (Notes 3, 4) unless otherwise noted.
CONDITIONS Operating Range FB1, FB2 < VFB FB1, FB2 > VFB, COUT = 1000pF Voltage Going Positive TA 0C TA < 0C
q q q q q q
MIN 2.7
TYP 170 1.1
MAX 27 540 3.5 0.898 0.907
UNITS V A mA V V A mV
0.862 0.853 -1
0.880 0.880 - 0.05 12
High-to-Low Transition FB1, FB2 > VFB
q q
1.75 1.64 0.78 1.11 1.35
2.05 1.94 110 0.865 1.185 1.50 260
2.35 2.24 0.95 1.26 1.65 650 22 26 22 26 40 8.0 3.3 0.45 28 28
VLKH VRST VTIM VTRIG ITRIG ITIM
FB1, FB2 > VFB FB1, FB2 > VFB FB1, FB2 > VFB FB1, FB2 < VFB FB1, FB2 < VFB, TIMER/RESET = VTRIG FB1 = (VFB + 30mV), FB2 < VFB FB1 = (VFB + 200mV), FB2 < VFB FB2 = (VFB + 30mV), FB1 < VFB FB2 = (VFB + 200mV), FB1 < VFB FB1, FB2 = (VFB + 200mV) 12V VCC 27V, FB1, FB2 > VFB, COUT = 1000pF VCC = 3.3V, FB1, FB2 > VFB, COUT = 1000pF FB1, FB2 < VFB, ISINK = 1mA, VCC = 3.3V FB1 > VFB, FB2 < VFB, TIMER/RESET = Open, COUT = 1000pF FB2 > VFB, FB1 < VFB, TIMER/RESET = Open, COUT = 1000pF
q q q q q q q q q q q q q q
4 5 4 5 8 4.8 2.7
10 12 10 12 18 6.3 3.2 7 7
VOUTH VOUTL tOVPD1 tOVPD2
OUT High Voltage OUT Low Voltage OUT Propagation Delay for FB1 OUT Propagation Delay for FB2
2
U
V V mV V V V A A A A A A V V V s s
W
U
U
WW
W
LTC1696
ELECTRICAL CHARACTERISTICS
SYMBOL tOVPD1,2 tr IOUTSC PARAMETER OUT Propagation Delay for FB1, FB2 OUT Rise Time OUT Short-Circuit Current
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. 2.7V VCC 27V (Notes 3, 4) unless otherwise noted.
CONDITIONS FB1, FB2 > VFB, TIMER/RESET = Open COUT = 1000pF FB1, FB2 > VFB, COUT = 1000pF 12V VCC 27V, FB1, FB2 > VFB, VOUT Shorted to GND VCC = 2.7V, FB1, FB2 > VFB, VOUT Shorted to GND
q q q q
MIN
TYP 6 0.4
MAX 24 3 160 18
UNITS s s mA mA
35 2
80 9
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC1696E is guaranteed to meet performance specifications from 0C to 70C. Specifications over the - 40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 4: All typical numbers are given for VCC = 12V and TA = 25C.
3
LTC1696 TYPICAL PERFOR A CE CHARACTERISTICS
Standby Supply Current vs Supply Voltage
200 180 160
SUPPLY CURRENT (A) SUPPLY CURRENT (mA)
TA = 25C
SUPPLY CURRENT (A)
140 120 100 80 60 40 20 0 0 5 15 20 10 SUPPLY VOLTAGE (V) 25 30
1696 G01
Active Supply Current vs Temperature
FB1, FB2 FEEDBACK THRESHOLD VOLTAGE (V) 1.20
0.8814 0.8811 0.8808 0.8805 0.8802 0.8799 0.8796
FB1, FB2 FEEDBACK THRESHOLD VOLTAGE (V)
VCC = 12V COUT = 1000pF
1.15
SUPPLY CURRENT (mA)
1.10
1.05
1.00
0.95 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G04
TIMER Threshold Voltage vs Supply Voltage
1.200
TIMER THRESHOLD VOLTAGE (V)
1.24
TA = 25C
TIMER THRESHOLD VOLTAGE (V)
1.195 1.190 1.185 1.180 1.175 1.170 1.165 1.160 0 5 20 15 SUPPLY VOLTAGE (V) 10 25 30
1696 G07
TIMER CURRENT (A)
4
UW
Standby Supply Current vs Temperature
200 190 180 170 160 150 140 130 120 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G02
Active Supply Current vs Supply Voltage
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5 20 15 10 SUPPLY VOLTAGE (V) 25 30
1696 G03
VCC = 12V
TA = 25C COUT = 1000pF
FB1, FB2 Feedback Threshold Voltage vs Supply Voltage
TA = 25C
FB1, FB2 Feedback Threshold Voltage vs Temperature
0.90 VCC = 12V
0.89
0.88
0.87
0.86
0
3
6
9 12 15 18 21 24 27 30 SUPPLY VOLTAGE (V)
1696 G05
0.85 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G06
TIMER Threshold Voltage vs Temperature
VCC = 12V 20 18
TIMER Current vs Supply Voltage
TA = 25C FB1 AND FB2 OVERDRIVE = 200mV 16 14 FB1 OR FB2 OVERDRIVE = 200mV 12 10 8
1.22
1.20
1.18
1.16
1.14 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G08
0
5
10 15 20 SUPPLY VOLTAGE (V)
25
30
1696 G09
LTC1696 TYPICAL PERFOR A CE CHARACTERISTICS
TIMER Current vs Temperature
22 20 VCC = 12V
TIMER CURRENT (A)
TIMER CURRENT (A)
18 16 14 12 10 FB1 OR FB2 OVERDRIVE = 200mV FB1 AND FB2 OVERDRIVE = 200mV
TIMER CURRENT (A)
8 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G10
Glitch Filter Timer vs Feedback Overdrive
25 VCC = 3.3V TA = 25C
GLITCH FILTER TIMER (s)
VCC = 12V TA = 25C
EXTERNAL TRIGGER TRESHOLD VOLTAGE (V)
GLITCH FILTER TIMER (s)
20
15 FB1 OR FB2 OVERDRIVE 10 FB1 AND FB2 OVERDRIVE 5
0
0
50 150 200 100 FEEDBACK OVERDRIVE (mV)
External Trigger Threshold Voltage vs Temperature
EXTERNAL TRIGGER THRESHOLD VOLTAGE (V) 1.505 1.500 VCC = 12V
RESET THRESHOLD VOLTAGE (V)
0.864 0.862 0.860 0.858 0.856 0.854 0.852 0 5 20 15 SUPPLY VOLTAGE (V) 10 25 30
1696 G17
RESET TRHESHOLD VOLTAGE (V)
1.495 1.490
1.485 1.480
1.475 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G16
UW
1696 G13
TIMER Current vs Feedback Overdrive
20 VCC = 12V TA = 25C
16
TIMER Current vs Feedback Overdrive
VCC = 3.3V TA = 25C FB1 AND FB2 OVERDRIVE
16
FB1 AND FB2 OVERDRIVE
14 12 FB1 OR FB2 OVERDRIVE 10 8 6 4
12
FB1 OR FB2 OVERDRIVE
8
4
0
0
50 150 200 100 FEEDBACK OVERDRIVE (mV)
250
1696 G11
0
50 100 150 200 FEEDBACK OVERDRIVE (mV)
250
1696 G12
Glitch Filter Timer vs Feedback Overdrive
30 25 20 15 10 5 0 FB1 OR FB2 OVERDRIVE FB1 AND FB2 OVERDRIVE
External Trigger Threshold Voltage vs Supply Voltage
1.51 1.50 1.49 1.48 1.47 1.46 1.45 1.44 0 5 20 15 10 SUPPLY VOLTAGE (V) 25 30
1696 G15
TA = 25C
250
0
50 100 150 200 FEEDBACK OVERDRIVE (mV)
250
1696 G14
RESET Threshold Voltage vs Supply Voltage
0.868 0.866 TA = 25C 0.880 0.875 0.870 0.865 0.860 0.855 0.850 0.845
RESET Threshold Voltage vs Temperature
VCC = 12V
0.840 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G18
5
LTC1696 TYPICAL PERFOR A CE CHARACTERISTICS
OUT Pin Active Output Voltage vs Supply Voltage
8
OUT PIN ACTIVE OUTPUT VOLTAGE (V)
OUT PIN SHORT-CIRCUIT CURRENT (mA)
OUT PIN ACTIVE OUTPUT VOLTAGE (V)
7 6 5 4 3 2 1 0 0
TA = 25C COUT = 1000pF
5
20 15 SUPPLY VOLTAGE (V)
10
OUT Pin Short-Circuit Current vs Temperature
120
OUT PIN SHORT-CIRCUIT CURRENT (mA) 30
VOUT SHORTED TO GND ACTIVE OUTPUT CURRENT (mA)
25 20 VCC = 5V 15 10 VCC = 2.7V 5 0
ACTIVE OUTPUT CURRENT (mA)
100 VCC = 27V 80 VCC = 12V 60 40 VCC = 5V 20 0 -55 -35 -15 VCC = 2.7V 5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G22
6
UW
25
1696 G19
OUT Pin Active Output Voltage vs Temperature
6.6 6.5 6.4 6.3 6.2 6.1 6.0 5.9 5.8 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1696 G20
OUT Pin Short-Circuit Current vs Supply Voltage
100 90 80 70 60 50 40 30 20 10 0 0 5 TA = 25C VOUT SHORTED TO GND 15 20 10 SUPPLY VOLTAGE (V) 25 30
1696 G21
VCC = 12V COUT = 1000pF
30
OUT Pin Active Output Current vs Output Voltage
TA = 25C
OUT Pin Active Output Current vs Output Voltage
100 90 80 70 60 50 40 30 20 10 0 VCC = 27V TA = 25C
VCC = 12V
0 0.5 1
1.5 2 2.5 3 3.5 4 OUTPUT VOLTAGE (V)
4.5
5
0
1
4 3 2 5 OUTPUT VOLTAGE (V)
6
7
1696 G24
1696 G23
LTC1696
PI FU CTIO S
FB1 (Pin 1): First Feedback Input. FB1 monitors and senses the first supply output voltage through an external resistor divider. This voltage is then compared with an internal reference voltage of 0.88V, which sets the threshold for an overvoltage fault detection. If the sense voltage exceeds the threshold level, the output response time at the OUT pin is dependent on the feedback overdrive above the threshold level. The higher the feedback overdrive, the faster will be the response time. GND (Pin 2): Power Ground. Return path for all device currents. VCC (Pin 3): Power Supply. The pin is connected separately from the power supply output that the chip is monitoring. Its input range is from 2.7V to 27V. The quiescent current is typically 100A in standby mode when the device is operating at 5V. The quiescent current increases to 170A when operating at 12V. OUT (Pin 4): Output Current Limit Driver. Capable of delivering continuous current, typically 80mA, at high supplies. The output current decreases with lower supply voltage. This pin directly drives the SCR crowbar at high supply voltage. It can also provide gate drive for an N-channel MOSFET or the base of an NPN transistor, which drives the gate of an external SCR at low supply voltage. It is normally in the inactive low state in the standby mode. In the event of an overvoltage fault condition, the OUT pin is latched into the active high state. The latched active high state is reset by pulling the TIMER/ RESET pin low through an N-channel MOSFET switch or if the supply voltage at the VCC pin goes below the undervoltage lockout threshold voltage of 1.94V. FB2 (Pin 5): Second Feedback Input. FB2 monitors and senses the second supply output voltage through an external resistor divider. This voltage is then compared with an internal reference voltage of 0.88V, which sets the threshold for an overvoltage fault detection. If the sense voltage exceeds the threshold level, the output response time at the OUT pin is dependent on the feedback overdrive above the threshold level. The higher the feedback overdrive, the faster will be the response time. TIMER/RESET (Pin 6): Glitch Filter Timer Capacitor, Reset and External Trigger Input. The external capacitor connected to this pin programs the internal glitch filter time delay. The internal current source used to charge the timer capacitor is typically 10A with feedback overdrive of less than 20mV above the feedback trip threshold from one feedback input. The current source increases to 12A when the feedback overdrive increases to more than 100mV. It further increases to 18A if larger overdrive occurs from both feedback inputs. The default glitch filter time delay without an external timer capacitor is fixed by an internal capacitor of 5pF with the internal reference voltage of 1.185V. The delay reduces with increases in first and second feedback input overdrive. This pin also serves as a reset input to clear the internal latch during an overvoltage fault condition. If pulled low, it resets the active high state of the internal latch. The reset signal to this pin should be an open drain type. This pin can also be driven high externally to activate the OUT pin active high if the FB1 and FB2 voltages remain below the feedback trip threshold.
U
U
U
7
LTC1696
BLOCK DIAGRA
VCC 3
GND 2
FB1 1 FB2 5
+ + - + -
BANDGAP REFERENCE 0.88V
GLITCH FILTER
LOGIC
+ -
0.865V
APPLICATIO S I FOR ATIO
Feedback Inputs
VS R2 FB1 R1 LTC1696
The LTC1696 has two feedback inputs that allow monitoring of two output voltages. The trip point of the internal comparator is set by an internal reference of 0.88V with 2% accuracy. The output voltage, VS, is sensed through an external resistor divider network (Figure 1). The resistors R1 and R2 values are calculated with the typical trip point of 0.88V. R1 * VS = 0.88 R1 + R2
R2 =
( VS - 0.88) * R1
0.88
As an example, let's calculate values for R1 and R2 for a 3.3V supply in which an overvoltage indication is required
at +10% (3.63V). First, a value for R1 is chosen based on the allowable resistor divider string current. This is determined by power dissipation requirements and possible sensitivity to noise coupling into the resistor divider. In this exercise, assume the resistor divider current is 20A. R1 is calculated from:
8
-
+
U
W
W
R4 INTERNAL 5V SUPPLY R2 R3
+ + -
VREF
-
R1
4 OUT
2V UVLO
1.185V INTERNAL 5V SUPPLY 10A + FUNCTION OF FB1 AND FB2 OVERDRIVE 6 TIMER/ RESET
1696 BD
UU
+ -
+ -
VREF = 0.88V
Figure 1
LTC1696
APPLICATIO S I FOR ATIO
R1 = VFB IDIVIDER = 0.88 V = 44k 20A
The nearest 1% value for R1 is 44.2k. Now, calculating for R2 yields:
R2 =
44.2k * (3.63V - 0.88 V ) = 138.1k 0.88 V
Choosing the nearest 1% value yields 137k. The chosen values for R1 and R2 yield an overvoltage threshold of 3.608V (+ 9.3%). With worst-case tolerances applied, the minimum overvoltage threshold is 3.481V (+5.5%) and the maximum overvoltage threshold is 3.738V (+13.3%). Reset Function In the event of an overvoltage condition, the OUT pin of the LTC1696 is latched into an active high state. The internal latch is reset by pulling the TIMER/RESET pin low through an external N-channel MOSFET switch or pulling VCC voltage below the UVLO trip point of 1.94V. Glitch Filter Timer The LTC1696 has a programmable glitch filter to prevent the output from entering its active high latched condition if transients occur on the FB1 or FB2 pins. The filter time delay is programmed externally by an external capacitor C1 connected to the TIMER/RESET pin.
VCC 3.3V
R2 54.9k 1% R1 44.2k 1% Q1 2N3904 R5 470 5% R6 22 5% SCR 2N6507
Figure 2. External SCR with NPN Emitter Follower with Low Voltage Supplies
U
The time delay is given by: tD =
W
UU
C1* VINT ICHG
where VINT is the internal reference voltage of 1.185V and ICHG is the internal current source charging the external capacitor C1. The current source ICHG charging the external timer capacitor is 10A for small feedback transients and increases to 12A for large feedback transients (greater than 100mV) from one feedback input. The charging current increases to 18A for large feedback transients from both feedback inputs. SCR Crowbar The LTC1696 can deliver continuous output current typically 80mA at high supply voltage to trigger an external SCR crowbar in the event of an overvoltage condition as shown in the typical application on the front page of the data sheet. The output current decreases when the supply voltage reduces. It delivers 25mA at a supply voltage of 5V. At a low supply voltage of 3.3V, the output current reduces to 10mA and an external NPN emitter follower is needed to boost the current in order to drive the SCR crowbar as shown in Figure 2. The power dissipation due to the high output current at high supply voltage can potentially exceed the thermal limit of the package. This is avoided by resetting the device rapidly when the external SCR crowbar has been triggered, so that the device is not kept in the active high state for too long.
POWER SUPPLY
VOUT2 2.5V VOUT1 1.8 V R4 93.1k 1% C1 1nF Q1 2N7002 RESET
1
FB1
TIMER/ 6 RESET LTC1696
2
GND
FB2
5 R3 44.2k 1%
3 C2 0.1F
VCC
OUT
4
1696 F02
9
LTC1696
APPLICATIO S I FOR ATIO
Back-to-Back N-Channel MOSFET
A power management circuit that uses the LTC1696 to control external back-to-back N-channel MOSFET at low supply voltage is shown in Figure 3. In standby mode, the drain of the external N-channel MOSFET, Q1, is pulled high
R2 38.3k 1% 1.5V R1 44.2k 1%
1
FB1
TIMER/ 6 RESET LTC1696
2
GND
VCC 3.3V
3 C2 0.1F
VCC
Figure 3. Back-to-Back N-Channel MOSFETs for Low Supply Application
10
U
by the power management controller when the LTC1696 OUT pin is in the low state. The LTC1696 drives the gate of Q1 high during an overvoltage fault condition. This pulls the drain of Q1 low and turns off the back-to-back Nchannel MOSFETs.
C1 1nF Q2 2N7002 RESET 1.8V R3 R4 44.2k 54.9k 1% 1% PRIMARY INPUT SUPPLY POWER MANAGEMENT CONTOLLER Q1 2N7002
1696 F03
W
UU
FB2
5
OUT
4
N-CHANNEL x2
LTC1696
PACKAGE DESCRIPTIO U
S6 Package 6-Lead Plastic SOT-23
(LTC DWG # 05-08-1634) (LTC DWG # 05-08-1636)
2.80 - 3.10 (.110 - .118) (NOTE 3) 2.60 - 3.00 (.102 - .118) 1.50 - 1.75 (.059 - .069) (NOTE 3) PIN ONE ID .95 (.037) REF .25 - .50 (.010 - .020) (6PLCS, NOTE 2) A A2 .09 - .20 (.004 - .008) (NOTE 2) 1.90 (.074) REF A1
S6 SOT-23 0401
SOT-23 (Original) A A1 A2 L .90 - 1.45 (.035 - .057) .00 - 0.15 (.00 - .006) .90 - 1.30 (.035 - .051) .35 - .55 (.014 - .021)
SOT-23 (ThinSOT) 1.00 MAX (.039 MAX) .01 - .10 (.0004 - .004) .80 - .90 (.031 - .035) .30 - .50 REF (.012 - .019 REF)
.20 (.008) DATUM `A'
L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES)
3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEC MO-193 FOR THIN
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.
11
LTC1696
APPLICATIO S I FOR ATIO
External Triggering The LTC1696 has a feature which allows the output to be latched into an active high state by pulling the TIMER/ RESET pin high even if both the feedback voltages at the
R2 38.3k 1% 1.5V R1 44.2k 1%
1
FB1
TIMER/ 6 RESET LTC1696
2
GND
VCC 3.3V
3 C2 0.1F
VCC
Figure 4. External Triggering
RELATED PARTS
PART NUMBER LTC1473 LTC1628 LT1681 LTC1698 LTC1703 LTC1735 LTC1922-1 LTC1960 DESCRIPTION Dual PowerPathTM Switch Driver High Efficiency, 2-Phase Synchronous Step-Down Switching Regulator Dual Transistor Synchronous Forward Controller Secondary Synchronous Rectifier Controller Dual 550k Synchronous 2-Phase Switching Regulator Controller with VID Synchronous Step-Down Switching Regulator Synchronous Phase Modulated Full-Bridge Controller Dual Battery Charger/Selector with SPI Interface COMMENTS For Systems with Multiple DC Sources, VIN Up to 30V, Inrush and Short-Circuit Protection Out-of-Phase Controllers, 3.5V VIN 36V, 1% Output Voltage Accuracy Operation Up to 72V Maximum Optocoupler Feedback with Pulse Transformer Synchronization Two Independent PWM Controllers, Wide Load Current Range, 1.5% Output Accuracy Current Mode, 3.5V VIN 36V, 0.5V VOUT 5V Output Power Levels from 50W to Several kW, Adaptive DirectSenseTM Zero Voltage Switching Extends Run Time, Reduces Charging Time, Crisis Management Prevents Power Interruption, 36-Pin SSOP
PowerPath and DirectSense are trademarks of Linear Technology Corporation.
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
www.linear.com
U
FB1 and FB2 pins are below the trip threshold of the internal comparator. The output is then reset by pulling the TIMER/RESET pin low. Figure 4 shows a circuit that uses the external triggering function of the LTC1696.
5V D1 1N4148 C1 1nF R5 6.8k 5% FB2 5 R3 44.2k 1% PRIMARY INPUT SUPPLY POWER MANAGEMENT CONTOLLER Q1 2N7002
1696 F04
W
UU
Q2 2N7002 R4 54.9k 1%
RESET
Q3 2N7002
TRIGGER
1.8V
OUT
4
N-CHANNEL x2
1696f LT/TP 0701 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2001

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