LT1431 Просмотр технического описания (PDF) - Linear Technology
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LT1431 Datasheet PDF : 14 Pages
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LT1431
Applications Information
Frequency Compensation
As a shunt regulator, the LT1431 is stable for all capacitive
loads on the COLL pin. Capacitive loading between 0.01µF
and 18µF causes reduced phase margin with some ringing
under transient conditions. Output capacitors should not
be used arbitrarily because output noise is not necessarily
reduced.
Excess capacitance on the REF pin can introduce enough
phase shift to induce oscillation when configured as a
reference >2.5V. This can be compensated with capacitance
between COLL and REF (phase lead). More complicated
feedback loops may require shaping of the frequency
response of the LT1431 with dominant pole or pole-zero
compensation. This can be accomplished with a capacitor or
series resistor and capacitor between COLL and COMP.
The compensation schemes mentioned above use voltage
feedback to stabilize the circuits. There must be voltage gain
at the COLL pin for them to be effective, so the COLL pin
must see a reasonable AC impedance. Capacitive loading
of the COLL pin reduces the AC impedance, voltage gain,
and frequency response, thereby decreasing the effective-
ness of the compensation schemes, but also decreasing
their necessity.
Typical Applications
2.5V Reference
3-Pin Package
RL
VIN
2.5V
CATHODE
REF
LT1431Z
ANODE
LT1431 TA02
2.5V Reference
8-Pin Package
RL
VIN
2.5V
V+
COLL
REF
LT1431
GND-S
GND-F
LT1431 TA03
5V Reference
RL
VIN
5V
V+
COLL
RTOP
LT1431
REF
RMID
GND-S
GND-F
LT1431 TA04
Increasing 5V Reference
RL
VIN
R
V+
COLL
RTOP
LT1431
REF
RMID
GND-S
GND-F
5V + ∆
LT1431 TA05
∆ = R • (0.5mA) ±25% PROCESS TOLERANCE
∆ ≤ 500mV
Programmable Reference with Adjustable
Current Limit
RL
VIN
V+
COLL
REF
LT1431
( ) VOUT =
1
+
R1
R2
VREF
R1
R2
GND-S
GND-F
RLIM
ILIMIT
=
0.7
RLIM +
3.6
AT
25°C
LT1431 TA06
1431fd
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