MC33264D-2.8 查看數據表（PDF） - ON Semiconductor
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MC33264D-2.8 Datasheet PDF : 10 Pages
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MC33264
Vin
3.3 μF
1
2
Vin
Control Input On/Off
8
Vout
7
Base N/C
3 On/Off
Gnd
6
4
R1
N/C
Adj
5
Vout
3.0, 3.3 or 5.0 V
3.3 μF
0.01
R2
Figure 7. Regulator Output Voltage Trim
The complete equation for the output voltage is:
ǒ Ǔ Vout + Vref
1)
R1
R2
) IFB R1
where Vref is the nominal 1.235 V reference voltage and IFB
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. IFB will produce a 2% typical error
in Vout which may be eliminated at room temperature by
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
In many applications it is desirable to reduce the noise
present at the output. Reducing the regulator bandwidth by
increasing the size of the output capacitor is the only method
for reducing noise.
Noise can be reduced fourfold by a bypass capacitor
across R1, since it reduces the high frequency gain from 4
to unity for the MC33264D−5.0. Pick
CBYPASS
+
2π
R1
1
x 200
Hz
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.
Unregulated Input
6.0 to 10 Vdc
0.1
Ground
TYPICAL APPLICATIONS
1
2
Vin
Control On/Off
8
Vout
Base
MC33264D−5.0
3
On/Off
7
N/C
4
N/C
Gnd Adj
6
5
1N4001
0.22
200 k
1%
100 k
1%
50 k
4.2 V ± 0.15 V
Lithium Ion
Rechargeable Cell
Figure 8. Lithium Ion Battery Cell Charger
http://onsemi.com
6
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