LP2950 Datasheet, PDF (10/14 Pages) National Semiconductor (TI) – Series of Adjustable Micropower Voltage Regulators

APPLICATION HINTS (Continued)
OUTPUT
VOLTAGE
4.75V
ERROR*
INPUT
VOLTAGE
5V
1.3V
FIGURE 1. ERROR Output Timing
*When VIN 1.3V the error flag pin becomes a high impedance,
and the error flag voltage rises to its pull-up voltage. Using Vout
as the pull-up voltage (see Figure 2), rather than an external 5V
source, will keep the error flag voltage under 1.2V (typ.) in this
condition. The user may wish to drive down the error flag
voltage using equal value resistors (10 k suggested), to ensure
a low-level logic signal during any fault condition, while still
allowing a valid high logic level during normal operation.
LP2950/LP2951
+V_IN
ERROR
OUPUT
100k
8
+V_IN
5 _ERROR*
V_OUT ¹
**SHUTDOWN
INPUT
3
SD
LP2951
GND
FB
4
7 _1.23V
V_OUT
1.2 30V
R₁
*+
.01
3.3µF
µF
V_REF
R₂
FIGURE 2. Adjustable Regulator
*See Application Hints.
Vout = VREF × (1 + R1/ R2)
**Drive with TTL- high to shut down. Ground or leave if shutdown
feature is not used.
Note: Pins 2 and 6 are left open.
TYPICAL APPLICATIONS
300 mA Regulator with 0.75 Dropout
UNREGULATED
INPUT
8
IN
1
OUT
330 Ω
LP2951
27kΩ
6 _VTAP
FB
7
SENSE ²
GND
4
4.7µ F
2N5432 (2)
5V OUTPUT
LOAD
50mA TO
300mA
Wide Input Voltage Range Current Limiter
+V_IN
8
ERROR
OUPUT
+V_IN
5 _ERROR
V_OUT ¹
LP2951
SHUTDOWN
INPUT
3
SD
GND
FB
4
7
*V_OUT ≈ V_ΙΝ
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on load
current. Current limit is typically 160 mA
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