Typical Performance Characteristics: continued
1.25
1.00
0.75
20.0
18.0
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
8.0
0.0
6.0
7.0
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
-V (V)
IN OUT
Short Circuit Current vs. VIN - VOUT
Dropout Voltage vs. Output Current
1.00
0.98
0.96
0.94
0.92
90.0
80.0
70.0
60.0
50.0
T
= 125°C
CASE
T
= 23°C
CASE
0.90
V
V
- V
= 2V
0.88
0.86
IN
Ripple
OUT
40.0
30.0
20.0
10.0
= 1V
PP
I
= 4A
OUT
0.84
0.82
C
C
= 0.1mF
= 22mF
Adj
T
= 0°C
OUT
CASE
0.80
1.00
2.00
3.00
– V
4.00
5.00
6
1
2
3
4
5
10
10
10
10
Frequency (Hz)
10
10
V
(V)
IN
OUT
Minimum Load Current vs. VIN - VOUT
Ripple Rejection vs. Frequency
Application Notes
output voltage is set according to the formula:
Theory of Operation
The CS5208-1 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
The term IAdj ´ R2 represents the error added by the adjust
pin current.
Adjustable Operation
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. The divider resistors
should be placed as close to the IC as possible and connect-
ed to the output with a separate metal trace.
Design Guidelines
This LDO adjustable regulator has an output voltage range
of 1.25V to 4.5V. An external resistor divider sets the out-
put voltage as shown in Figure 1. The regulatorÕs voltage
sensing error amplifier maintains a fixed 1.25V reference
between the output pin and the adjust pin.
A resistor divider network R1 and R2 causes a fixed current
to flow to ground. This current creates a voltage across R2
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
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
