CS5203A-1 データシートの表示（PDF） - ON Semiconductor

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CS5203A-1

3.0 A Adjustable, and Fixed 1.5 V, 3.3 V and 5.0 V Linear Regulators

ON Semiconductor 

CS5203A−1, CS5203A−2, CS5203A−3, CS5203A−5

100

90

80

70

60

50

40

TCASE = 25°C

30

IOUT = 3.0 A

(VIN − VOUT) = 3.0 V

20

VRIPPLE = 1.6 VPP

10

CAdj = 25 mF

0

101

102

103

104

105

Frequency (Hz)

Figure 9. Ripple Rejection vs. Frequency

(Adjustable Versions)

APPLICATIONS INFORMATION

The CS5203A family of linear regulators provides fixed

or adjustable voltages at currents up to 3.0 A. The regulators

are protected against short circuit, and include thermal

shutdown and safe area protection (SOA) circuitry. The

SOA protection circuitry decreases the maximum available

output current as the input−output differential voltage

increases.

The CS5203A 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.

VIN

C1

VIN

VOUT

CS5203A−1

Adj

VREF

R1

VOUT

C2

IAdj

R2

CAdj

Adjustable Operation

The adjustable regulator (CS5203A−1) has an output

voltage range of 1.25 V to 13 V. An external resistor divider

sets the output voltage as shown in Figure 10. The regulator

maintains a fixed 1.25 V (typical) 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 1.25 V across R1 and sets the

overall output voltage. The adjust pin current (typically

50 mA) 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:

ǒ Ǔ VOUT + VREF

R1 ) R2

R1

) IAdj

R2

The term IAdj × R2 represents the error added by the adjust

pin current.

R1 is chosen so that the minimum load current is at least

10 mA. R1 and R2 should be the same type, e.g. metal film

for best tracking over temperature. The adjust pin is

bypassed to improve the transient response and ripple

rejection of the regulator.

Figure 10. Resistor Divider Scheme for the

Adjustable Version

Stability Considerations

The output or compensation capacitor helps determine

three main characteristics of a linear regulator: satrtup delay,

load transient response and loop stability.

The capacitor value and type is based on cost, availability,

size and temperature constraints. A tantalum or aluminum

electrolytic capacitor is best, since a film or ceramic

capacitor with almost zero ESR, can cause instability. The

aluminum electrolytic capacitor is the least expensive

solution. However, when the circuit operates at low

temperatures, both the value and ESR of the capacitor will

vary considerably. The capacitor manufacturers data sheet

provides this information.

A 22 mF tantalum capacitor will work for most

applications, but with high current regulators such as the

CS5203A the transient response and stability improve with

higher values of capacitor. The majority of applications for

this regulator involve large changes in load current so the

output capacitor must supply the instantaneous load current.

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