Typical Performance Characteristics: continued
20.0
18.0
1.25
1.00
0.75
16.0
14.0
12.0
10.0
8.0
0.50
0.25
0.00
6.0
4.0
2.0
0.0
1.0
2.0
3.0
4.0
5.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
0.0
6.0
7.0
V
-V (V)
IN OUT
Output Current (A)
Dropout Voltage vs. Output Current
Short Circuit Current vs. VIN - VOUT
90.0
80.0
70.0
60.0
50.0
1.00
0.98
0.96
0.94
0.92
T
CASE
= 125°C
T
CASE
= 23°C
0.90
V
V
- V
= 2V
IN
Ripple
OUT
40.0
30.0
20.0
10.0
0.88
0.86
= 1V
PP
I
= 4A
OUT
C
C
= 0.1mF
= 22mF
Adj
0.84
0.82
OUT
T
CASE
= 0°C
0.80
6
1
2
3
4
5
10
10
10
10
Frequency (Hz)
10
10
1.00
2.00
3.00
– V
4.00
5.00
V
(V)
IN
OUT
Minimum Load Current vs. VIN - VOUT
Ripple Rejection vs. Frequency
Application Notes
that adds to the 1.25V across R1 and sets the overall output
voltage. The adjust pin current (typically 50µA) also flows
through R2 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:
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.
R1 + R2
VOUT = VREF
´
+ R2 ´ IAdj
R1
Adjustable Operation
Design Guidelines
The term IAdj ´ R2 represents the error added by the adjust
pin current.
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.
R1 is chosen so that the minimum load current is a least
10mA. R1 and R2 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.
A resistor divider network R1 and R2 causes a fixed current
to flow to ground. This current creates a voltage across R2
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
