contact-fact Micrel Semiconductor, contact-fact Datasheet - Page 11

• Manufacturer Part Number: contact-fact
• Description: Mic2950/mic2951 150ma Low-dropout Voltage Regulator
• Manufacturer: Micrel Semiconductor

Noise can be reduced fourfold by a bypass capacitor across
R
Pick:
* SEE APPLICATIONS INFORMATION
Typical Applications
*HIGH INPUT LOWERS V
July 2005
MIC2950/2951
ERROR
OUTPUT
*SLEEP
INPUT
ON
SHUTDOWN
INPUT
1
, since it reduces the high frequency gain from 4 to unity.
OUTPUT
VOLTAGE
ERROR
INPUT
VOLTAGE
C
OFF
5V Regulator with 2.5V Sleep Function
47kΩ
BYPASS
5
3
Figure 1. ERROR Output Timing
SD
ERROR
NOT *
VALID
GND
4
OUT
MIC2951
≅
4.75V
+V IN
TO 2.5V
+V IN
2 R
1.3V
π
8
1
5V
V
7
FB
OUT
• 200 Hz
1
1
C-MOS
GATE
100pF
2N3906
470 kΩ
NOT *
VALID
200kΩ
1%
100kΩ
1%
100kΩ
+V OUT
+
3.3µF
11
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 improve-
ments are more dramatic at higher output voltages.
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40
ON
NOTE: PINS 2 AND 6 ARE LEFT OPEN
DEPENDING ON LOAD CURRENT.
E R R O R
O UTPUT
SHUTDOWN
INPUT
ON
ERROR
OUTPUT
SHUTDOWN
INPUT
Wide Input Voltage Range Current Limiter
O F F
100kΩ
Figure 2. Adjustable Regulator
5
3
E R R O R
S D
OFF
5
3
GND
ERROR
SD
MIC2951
4
GND
+V
8
V
IN
MIC2951
4
IN
V
+V IN
+V IN
F B
R E F
V
7
8
OUT
1.23V
V
FB
OUT
7
1
*SEE APPLICATIONS
INFORMATION
1
R 100
m
R
V
1.2
1
V TO 400
OUT
2
*V
MIC2950/2951
pF
V
OUT
x (1 +
OUT
30V
Micrel, Inc.
m
3.3µF
≈V IN
V,
= V
R
R
1
2
R E F
)