ltc1642a Linear Technology Corporation, ltc1642a Datasheet
ltc1642a
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ltc1642a Summary of contents
Page 1
... The RESET output can generate a system reset with adjustable delay when the supply volt- age falls below an adjustable threshold. The ON pin cycles the board power. The LTC1642A is available in the 16-pin SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners ...
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... ON, FB, OV, COMP , COMP RESET, FAULT, COMPOUT .....................– 0.3V to 18.5V Operating Temperature Range LTC1642AC ............................................. 0°C to 70°C LTC1642AI ......................................... – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are unless otherwise specified ...
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... REF REF REF ∆ GATE 25° (V) CC 1642a G26 LTC1642A = 25°C. A MIN TYP MAX UNITS ● ● ● ● µA ● 0.5 µA ● ...
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... LTC1642A W U TYPICAL PERFOR A CE CHARACTERISTICS I Pull-Up Current vs V GATE GATE T = 25° (V) CC 1642a G23 CRWBR Driver Current 2 25°C A 1.6 1.2 0.8 0 (V) CC 1642a G35 FB Threshold Voltage 1.232 T = 25° ...
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... TEMPERATURE (° 25° (V) CC LTC1642A FAULT and RESET V OL Temperature 3 5mA OL 3.0 2.5 2 1.5 = 12V 1.0 = 15V 0.5 0 100 125 –50 – TEMPERATURE (°C) 1642a G16 ON Pin Threshold Voltage vs Temperature 1 ...
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... LTC1642A CTIO S CRWBR (Pin 1): Overvoltage Crowbar Circuit Timer and Trigger. This pin controls an external overvoltage crowbar circuit. A capacitor from the pin to ground sets a 9ms/µF delay after an overvoltage occurs until an external SCR is triggered. See Applications Information. Ground the CRWBR pin if unused. ...
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... V voltages up to 33V. In this case the GATE pin voltage will usually be low but this is not guaranteed; use the OV pin to ensure that the pass device is off. The V provides a high side connection to the SENSE resistor. LTC1642A and SENSE pin ...
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... LTC1642A W BLOCK DIAGRA 23mV TO 53mV – – + SENSE 15 – 21V + 1.22V + OV 9 21V – 1.22V + ON 4 21V – 1.22V + V CC – 2. COMP 11 – – COMP 12 21V 21V 8 GATE 14 21.5V CHARGE PUMP 45µA 25µA 1.5mA RISING DELAY 15µs TO 100µs ...
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... The LTC1642A limits the charging currents drawn by a board’s capacitors, allowing safe insertion into a live backplane. In the circuit shown in Figure 1 the LTC1642A and the external NMOS pass transistor Q1 work together to limit charging currents. Waveforms at board insertion are shown in Figure 2. When power is first applied to V chip holds Q1’ ...
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... U pin low for at least 2µs and FAULT will go high. Then take ON high again and the GATE will ramp up after a system timing cycle. Or, configure the LTC1642A to restart itself after the circuit breaker trips by connecting FAULT to the ON pin, as shown in the next section. The servo loop controlling Q1 during current limit has a unity-gain frequency of about 125kHz ...
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... U APPLICATIO S I FOR ATIO Automatic Restart After the Circuit Breaker Opens The LTC1642A will automatically attempt to restart itself after the circuit breaker opens if the FAULT output is tied to the ON pin. The circuit is shown in Figure 5. Diode D1 blocks the weak FAULT pull-up current source from unbal- ancing the R6-R5 divider ...
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... Figure 8. Overvoltage Protection Circuitry Once the CRWBR timer trips the LTC1642A latches off: after the overvoltage clears GATE and FAULT remain at ground and CRWBR continues sourcing 1.5mA. To restart the part after the overvoltage clears, hold the ON pin low for at least 2µs and then bring it high. The GATE voltage will begin ramping up one system timing cycle later ...
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... OV is connected to the output of the N-Channel pass transistor, the LTC1642A will automatically restart even if FAULT is not tied to ON. If the divider is connected to the input side, the LTC1642A will restart itself only if FAULT is tied to ON, and only after the overvoltage clears. The OV and FB Comparators ...
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... Figure 14. Minimum REF Compensation vs REF Current Reference The LTC1642A’s internal voltage reference is buffered and brought out to the REF pin. The buffer amplifier should be falls below the chip’s compensated with a capacitor connected between REF and ground current is drawn from REF, 0.1µF ...
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... In high current applications, the voltage drop along traces can be appreciable. Connect the LTC1642A’s V SENSE pins directly across sense resistor R2 to prevent the power trace’s resistance from adding to R2 also + – ...
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... R3 R12 330Ω 100Ω 84. 127k 1N4705 1% 18V SENSE GATE COMP LTC1642A R11 12.4k – REF COMP CRWBR RST TMR BRK TMR C1* 0.01µF 0.033µF C6 0.1µF C4 0.033µF 10k START-UP DELAY IS 20ms TYPICAL CIRCUIT-BREAKER DELAY IS 1ms TYPICAL † ...