Datasheet LT1431 (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | Programmable Reference |
| Pages / Page | 14 / 7 — applicaTions inForMaTion. Frequency Compensation. Typical applicaTions. … |
| File Format / Size | PDF / 233 Kb |
| Document Language | English |
applicaTions inForMaTion. Frequency Compensation. Typical applicaTions. 2.5V Reference. 3-Pin Package. 8-Pin Package. 5V Reference
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Text Version of Document
LT1431
applicaTions inForMaTion Frequency Compensation
response of the LT1431 with dominant pole or pole-zero As a shunt regulator, the LT1431 is stable for all capacitive compensation. This can be accomplished with a capacitor loads on the COLL pin. Capacitive loading between 0.01µF or series resistor and capacitor between COLL and COMP. and 18µF causes reduced phase margin with some ringing The compensation schemes mentioned above use voltage under transient conditions. Output capacitors should not feedback to stabilize the circuits. There must be voltage gain be used arbitrarily because output noise is not necessar- at the COLL pin for them to be effective, so the COLL pin ily reduced. must see a reasonable AC impedance. Capacitive loading Excess capacitance on the REF pin can introduce enough of the COLL pin reduces the AC impedance, voltage gain, phase shift to induce oscillation when configured as a and frequency response, thereby decreasing the effective- reference >2.5V. This can be compensated with capacitance ness of the compensation schemes, but also decreasing between COLL and REF (phase lead). More complicated their necessity. feedback loops may require shaping of the frequency
Typical applicaTions 2.5V Reference 2.5V Reference 3-Pin Package 8-Pin Package 5V Reference
RL RL RL VIN VIN VIN 2.5V 2.5V 5V CATHODE V+ COLL V+ COLL REF REF RTOP REF LT1431Z LT1431 LT1431 RMID ANODE GND-S GND-F GND-S GND-F LT1431 TA03 LT1431 TA04 LT1431 TA02
Programmable Reference with Adjustable Increasing 5V Reference Current Limit
RL RL VIN VIN 5V + ∆ VOUT = (1 + R1 V R2) REF R V+ COLL R1 V+ COLL RTOP REF LT1431 REF R LT1431 MID R2 GND-S GND-F GND-S GND-F LT1431 TA05 RLIM ∆ = R • (0.5mA) ±25% PROCESS TOLERANCE ILIMIT = 0.7 AT 25°C RLIM + 3.6 ∆ ≤ 500mV LT1431 TA06 1431fe 7 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Schematic Diagram Package Description Revision History Package Description Related Parts
applicaTions inForMaTion Frequency Compensation
response of the LT1431 with dominant pole or pole-zero As a shunt regulator, the LT1431 is stable for all capacitive compensation. This can be accomplished with a capacitor loads on the COLL pin. Capacitive loading between 0.01µF or series resistor and capacitor between COLL and COMP. and 18µF causes reduced phase margin with some ringing The compensation schemes mentioned above use voltage under transient conditions. Output capacitors should not feedback to stabilize the circuits. There must be voltage gain be used arbitrarily because output noise is not necessar- at the COLL pin for them to be effective, so the COLL pin ily reduced. must see a reasonable AC impedance. Capacitive loading Excess capacitance on the REF pin can introduce enough of the COLL pin reduces the AC impedance, voltage gain, phase shift to induce oscillation when configured as a and frequency response, thereby decreasing the effective- reference >2.5V. This can be compensated with capacitance ness of the compensation schemes, but also decreasing between COLL and REF (phase lead). More complicated their necessity. feedback loops may require shaping of the frequency
Typical applicaTions 2.5V Reference 2.5V Reference 3-Pin Package 8-Pin Package 5V Reference
RL RL RL VIN VIN VIN 2.5V 2.5V 5V CATHODE V+ COLL V+ COLL REF REF RTOP REF LT1431Z LT1431 LT1431 RMID ANODE GND-S GND-F GND-S GND-F LT1431 TA03 LT1431 TA04 LT1431 TA02
Programmable Reference with Adjustable Increasing 5V Reference Current Limit
RL RL VIN VIN 5V + ∆ VOUT = (1 + R1 V R2) REF R V+ COLL R1 V+ COLL RTOP REF LT1431 REF R LT1431 MID R2 GND-S GND-F GND-S GND-F LT1431 TA05 RLIM ∆ = R • (0.5mA) ±25% PROCESS TOLERANCE ILIMIT = 0.7 AT 25°C RLIM + 3.6 ∆ ≤ 500mV LT1431 TA06 1431fe 7 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Schematic Diagram Package Description Revision History Package Description Related Parts
