MIC2920A/29201/29202/29204
tor from 1µF to 220µF only decreases the noise from 430µV
to 160µV
RMS
for a 100kHz bandwidth at 5V output. Noise can
be reduced fourfold by a bypass capacitor across R
1
, since it
reduces the high frequency gain from 4 to unity. Pick
1
C
BYPASS
=
2
πR1
• 200 Hz
or about 0.01µF. When doing this, the output capacitor must
be increased to 10µF to maintain stability. These changes re-
duce the output noise from 430µV to 100µV rms for a 100kHz
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 MIC2920A 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
V IN
100kΩ
+V IN
8
V
IN
+V IN
V OUT
V OUT
V
OUT
1
V OUT
= 5V
ERROR
O U T PU T
SHUTDOWN
INPUT
ON
5
ERROR
1.2
26V
+
10µF
GND
3
SHUTDOWN
GND ADJU ST
7
4
1.23V
OFF
R 1 100
pF
10µF
V OUT = V R E F x (1 +
R1
)
R2
VREF
R2
NOTE: PINS 2 AND 6 ARE LEFT OPEN
Figure 2. MIC2920A-5.0 Fixed +5V Regulator
Figure 3. MIC29202/29204 Adjustable Regulator. Pinout is for
MIC29204.
≥
5.3V
+V IN
8
+VIN
ERROR
OUTPUT
SHUTDOWN
INPUT
ON
8
+V IN
V CC OUT
5 ERROR
VOUT
1
*V OUT
= V IN
SHUTDOWN
INPUT
HIGH = OFF
3
V
OUT
SHUT-
DOWN
1
+
3
SD
GND ADJ U ST
4
7
LOW = ON
100pF
OFF
GND
4
ADJUST
7
220kΩ
1%
300kΩ
1%
10µF
HIGH = 5V OUT
470 kΩ
180kΩ
1%
* Minimum Input-Output Voltage ranges from 40mV to 400mV, depending on load current
LOW = 3.3V OUT
2N2222
PIN 3 LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF = 5.0V.
Figure 4. MIC29204 Wide Input Voltage Range Current Limiter
Figure 5. MIC29202/29204 5.0V or 3.3V Selectable Regulator
with Shutdown. Pinout is for MIC29204.
February 2005
9
M9999-021505
MICREL [ MICREL SEMICONDUCTOR ]
