MIC2937 Datasheet, PDF (9/12 Pages) Micrel Semiconductor – 750mA Low-Dropout Voltage Regulator

MIC2937A/29371/29372
with a bypass capacitor across R₁, since it reduces the high
frequency gain from 4 to unity. Pick
CBYPASS ≅
1
2 πR1 • 200 Hz
or about 0.01µF. When doing this, the output capacitor must
be increased to 10µF to maintain stability. These changes
reduce the output noise from 430µV to 100µV_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.
Micrel, Inc.
Automotive Applications
The MIC2937A is ideally suited for automotive applications
for a variety of reasons. It will operate over a wide range of
input voltages with very low dropout voltages (40mV at light
loads), and very low quiescent currents (100µA typical). These
features are necessary for use in battery powered systems,
such as automobiles. It is a “bulletproof” device with the abil-
ity to survive both reverse battery (negative transients up to
20V below ground), and load dump (positive transients up to
60V) conditions. A wide operating temperature range with low
temperature coefficients is yet another reason to use these
versatile regulators in automotive designs.
Typical Applications
VIN
+VIN
VOUT
VOUT = 5V
GND
+
10µF
Figure 2. MIC2937A-5.0 Fixed +5V Regulator
VIN
VOUT
VOUT
1.2V 26V
SHUTDOWN
SHUTDOWN
INPUT
OFF
GND ADJUST
ON
1.23V
R1
.01
µF
10µF
VOUT = VREF x (1 +
R1
R2
)
VREF
R2
Figure 3. MIC29372 Adjustable Regulator
+VIN
VIN
VOUT
VOUT ≈ VIN
+5V to +7V
SHUTDOWN
INPUT
OFF
+V _IN
SHUTDOWN
VOUT
ON
GND ADJUST
VCC OUT
100pF
+
300k Ω
1%
10µF
GND ADJUST
3.3V
5V
Input Output
0
3.3V
1
5.0V
470 k Ω
220k Ω
1%
180k Ω
1%
2N2222
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
SHUTDOWN PIN LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF = 5.0V.
Figure 4. MIC29372 Wide Input Voltage Range Current Limiter
Figure 5. MIC29372 5.0V or 3.3V Selectable Regulator with
Shutdown.
May 2006
9
MIC2937A/29371/29372