CS5207A-1
Typical Performance Characteristics: continued
1.25
20.0
18.0
1.00
16.0
Output Current (A)
Dropout Voltage (V)
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.75
0.50
0.25
0.00
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Output Current (A)
V
IN
-V
OUT
(V)
Dropout Voltage vs. Output Current
Short Circuit Current vs. V
IN
- V
OUT
90.0
1.00
0.98
Minimum Load Current (mA)
0.96
0.94
0.92
0.90
0.88
0.86
0.84
0.82
0.80
1.00
2.00
3.00
V
IN
– V
OUT
(V)
4.00
5.00
10
T
CASE
= 0°C
T
CASE
= 23°C
T
CASE
= 125°C
Ripple Rejection (dB)
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
1
V
IN
- V
OUT
= 2V
V
Ripple
= 1V
PP
I
OUT
= 4A
C
Adj
= 0.1mF
C
OUT
= 22mF
10
2
10
3
10
4
10
5
10
6
Frequency (Hz)
Minimum Load Current vs. V
IN
- V
OUT
Ripple Rejection vs. Frequency
Application Notes
Theory of Operation
The CS5207A-1 linear regulator has a composite PNP-NPN
output stage that requires an output capacitor for stability.
A detailed procedure for selecting this capacitor is includ-
ed in the Stability Considerations section.
Adjustable Operation
that adds to the 1.25V across R
1
and sets the overall output
voltage. The adjust pin current (typically 50µA) also flows
through R
2
and adds a small error that should be taken
into account if precise adjustment of Vout is necessary. The
output voltage is set according to the formula:
V
OUT
= V
REF
´
R
1
+ R
2
+ R
2
´
I
Adj
R
1
Design Guidelines
This LDO adjustable regulator has an output voltage range
of 1.25V to 5V. An external resistor divider sets the output
voltage as shown in Figure 1. The regulatorÕs voltage sens-
ing error amplifier maintains a fixed 1.25V reference
between the output pin and the adjust pin.
A resistor divider network R
1
and R
2
causes a fixed current
to flow to ground. This current creates a voltage across R
2
The term I
Adj
´
R
2
represents the error added by the adjust
pin current.
R
1
is chosen so that the minimum load current is a least
10mA. R
1
and R
2
should be of the same composition for
best tracking over temperature. For best results, the divider
resistor should be placed near the regulator with a separate
metal trace connecting them to output.
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
