CS5201-1
Typical Performance Characteristics: continued
70.0
I
O
= 10mA
Ripple Rejection (dB)
65.0
Adjust Pin Current (mA)
85
75
65
55
45
35
25
15
0
10
20
30
40
50
60
70
80
90 100 110 120 130
10
1
10
2
10
3
10
4
10
5
10
6
Temperature (°C)
60.0
55.0
50.0
T
CASE
= 25°C
I
OUT
= 1A
(V
IN
Ð V
OUT
) = 3V
V
RIPPLE
= 1.0V
PP
C
Adj
= 0.1mF
45.0
40.0
Frequency (Hz)
Adjust Pin Current vs. Temperature
Ripple Rejection vs. Frequency
Voltage Deviation (mV)
3.5
200
100
0
-100
-200
V
OUT
= 3.3V
C
OUT=
C
IN
= 22mF Tantalum
C
Adj=
0.1mF
3.3
3.1
2.9
2.7
I
SC
(A)
9
10
2.5
2.3
2.1
1.9
1.7
Load Step (mA)
1000
500
0
0
1
2
3
4
5
Time
mS
6
7
8
1.5
1.0
1.5
2.0
2.5
V
IN
- V
OUT
(V)
3.0
3.5
4.0
Transient Response
Short Circuit Current vs. V
IN
- V
OUT
Applications Information
The CS5201-1 linear regulator provides adjustable volt-
ages at currents up to 1A. The regulator is protected
against overcurrent conditions and includes thermal
shutdown.
The CS5201-1 has a composite PNP-NPN output transistor
and requires an output capacitor for stability. A detailed
procedure for selecting this capacitor is included in the
Stability Considerations section.
Adjustable Operation
50µA) also flows through R2 and adds a small error that
should be taken into account if precise adjustment of V
OUT
is necessary.
The output voltage is set according to the formula:
V
OUT
= V
REF
´
R1 + R2 + I
Adj
´
R2
R1
The term I
Adj
´
R2 represents the error added by the adjust
pin current.
R
1
is chosen so that the minimum load current is at least
2mA. R1 and R2 should be the same type, e.g. metal film
for best tracking over temperature. While not required, a
bypass capacitor from the adjust pin to ground will
improve ripple rejection and transient response. A 0.1µF
tantalum capacitor is recommended for Òfirst cutÓ design.
Type and value may be varied to obtain optimum perfor-
mance vs. price.
(
)
The CS5201-1 has an output voltage range of 1.25V to 5.5V.
An external resistor divider sets the output voltage as
shown in Figure 1. The regulator maintains a fixed 1.25V
(typical) reference between the output pin and the adjust
pin.
A resistor divider network R1 and R2 causes a fixed cur-
rent 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
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
