MIC2950 Datasheet, PDF (11/14 Pages) Micrel Semiconductor – 150mA Low-Dropout Voltage Regulator

MIC2950/2951
Noise can be reduced fourfold by a bypass capacitor across
R , since it reduces the high frequency gain from 4 to unity.
1
Pick:
CBYPASS ≅
1
2 πR1 • 200 Hz
Micrel
or about 0.01 µF. When doing this, the output capacitor must
be increased to 3.3 µF to maintain stability. These changes
reduce the output noise from 430 µV to 100 µV rms for a 100
kHz bandwidth at 5V output. With the bypass capacitor
added, noise no longer scales with output voltage so that
improvements are more dramatic at higher output voltages.
OUTPUT
VOLTAGE
4.75V
ERROR ^NOT *
VALID
INPUT
VOLTAGE
5V
1.3V
N_*OT
VALID
* SEE APPLICATIONS INFORMATION
Figure 1. ERROR Output Timing
Typical Applications
ERROR
OUTPUT
+VIN
100kΩ
8
VIN
5 _ERROR
VOUT ¹
VOUT = V _REF
x (1 +
R1
R2
)
VOUT
1.2 30V
MIC2951
SHUTDOWN
INPUT
3
SD
OFF
GND FB
3.3µF
R1 100
pF
ON
4
7
1.23V
3
VREF
R2
NOTE: PINS 2 AND 6 ARE LEFT OPEN
*SEE APPLICATIONS
INFORMATION
Figure 2. Adjustable Regulator
870 23
*SLEEP
INPUT
+V _IN
C-MOS
GATE
47kΩ
8
+V _IN
ERROR
OUTPUT
5 _ERROR
VOUT ¹
MIC2951
SHUTDOWN
INPUT
3
SD
OFF
GND
FB
ON
4
7
470 kΩ
+V _OUT
2N3906
100pF
200kΩ
1% ₊
100kΩ
3.3µF
1%
100kΩ
*HIGH INPUT LOWERS V_OUT TO 2.5V
5V Regulator with 2.5V Sleep Function
+VIN
8
ERROR
OUTPUT
+VIN
870 25
5 _{ERROR VOUT} ^{1 *VOUT ≈VIN}
MIC2951
SHUTDOWN
INPUT
3
SD
OFF
GND FB
ON
4
7
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
Wide Input Voltage Range Current Limiter
February 1999
3-59