mc33264dm ON Semiconductor, mc33264dm Datasheet - Page 6

• Manufacturer Part Number: mc33264dm
• Description: Low Dropout Micropower Voltage Regulators With On/off Control
• Manufacturer: ON Semiconductor

where V
is the feedback pin bias current, nominally −20 nA. The
minimum recommended load current of 1.0 μA forces an
upper limit of 1.2 MΩ on the value of R2, if the regulator
must work with no load. I
in V
adjusting R1. For better accuracy, choosing R2 = 100 K
reduces this error to 0.17% while increasing the resistor
program current to 12 μA.
Output Noise
present at the output. Reducing the regulator bandwidth by
The complete equation for the output voltage is:
In many applications it is desirable to reduce the noise
out
Unregulated Input
which may be eliminated at room temperature by
ref
6.0 to 10 Vdc
is the nominal 1.235 V reference voltage and I
Ground
V out + V
0.1
Control Input
ref
3.3 μF
FB
Control
1 ) R1
will produce a 2% typical error
2
3
2
3
R2
On/Off
On/Off
On/Off
On/Off
MC33264D−5.0
6
) I
Gnd
Gnd
Figure 8. Lithium Ion Battery Cell Charger
FB
6
Figure 7. Regulator Output Voltage Trim
V
in
1
V
V
R1
5
in
in
Adj
1
Base
TYPICAL APPLICATIONS
V
out
Adj
5
Base
V
8
7
4
http://onsemi.com
out
N/C
N/C
FB
4
8
7
N/C
N/C
6
increasing the size of the output capacitor is the only method
for reducing noise.
across R1, since it reduces the high frequency gain from 4
to unity for the MC33264D−5.0. Pick
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 Vrms for a
100 kHz bandwidth for the 5.0 V output device. With the
bypass capacitor added, noise no longer scales with output
voltage so that improvements are more dramatic at higher
output voltages.
Noise can be reduced fourfold by a bypass capacitor
R1
0.22
R2
1N4001
C
0.01
BYPASS
3.3 μF
+
100 k
1%
50 k
200 k
1%
2π R1 x 200 Hz
V
3.0, 3.3 or 5.0 V
out
1
Rechargeable Cell
4.2 V ± 0.15 V
Lithium Ion