LP3982IMM-2.5 National Semiconductor, LP3982IMM-2.5 Datasheet - Page 6

• Manufacturer Part Number: LP3982IMM-2.5
• Description: IC,VOLT REGULATOR,FIXED,+2.5V,CMOS,TSSOP,8PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LP3982IMM-2.5

• Rohs Compliant: NO

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Typical Performance Characteristics
2.2µF, C
Application Information
GENERAL INFORMATION
LP3982 is package, pin and performance compatible with
Maxim’s MAX8860 excluding reverse battery protection and
Dual Mode
Figure 1 shows the functional block diagram for the LP3982.
A 1.25V bandgap reference, an error amplifier and a PMOS
pass transistor perform voltage regulation while being sup-
ported by shutdown, fault, and the usual Temperature and
current protection circuitry
The regulator’s topology is the classic type with negative
feedback from the output to one of the inputs of the error
amplifier. Feedback resistors R
external to the IC, depending on whether it is the fixed
voltage version or the adjustable version. The negative feed-
back and high open loop gain of the error amplifier cause the
two inputs of the error amplifier to be virtually equal in
voltage. If the output voltage changes due to load changes,
the error amplifier provides the appropriate drive to the pass
transistor to maintain the error amplifier’s inputs as virtually
equal. In short, the error amplifier keeps the output voltage
constant in order to keep its inputs equal.
FIGURE 1. Functional Block Diagram for the LP3982
CC
™
= 33nF, T
function (fixed and adjustable combined).
Power-Up Response
J
= 25˚C, V
1
and R
SHDN
2
= V
are either internal or
IN
. (Continued)
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20036913
Unless otherwise specified, V
6
OUTPUT VOLTAGE SETTING (ADJ VERSION ONLY)
The output voltage is set according to the amount of nega-
tive feedback (Note that the pass transistor inverts the feed-
back signal.) Figure 2 simplifies the topology of the LP3982.
This type of regulator can be represented as an op amp
configured as non-inverting amplifier and a fixed DC Voltage
(V
op amp is its extra-large output transistor that only sources
current. In terms of its non-inverting configuration, the output
voltage equals V
Utilize the following equation for adjusting the output to a
particular voltage:
Choose R
jection, noise and power consumption.
REF
) for its input signal. The special characteristic of this
FIGURE 2. Regulator Topology Simplified
2
= 100k to optimize accuracy, power supply re-
Power-Down Response
REF
times the closed loop gain:
IN
= V
O
+ 0.5V, C
IN
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= C
OUT
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=