CS52015-3GDPR3 datasheet(4/6 Pages) CHERRY

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Applications Information

The CS52015-3 linear regulator provides a 3.3V output

voltage at currents up to 1.5A. The regulator is protected

against overcurrent conditions and includes thermal

shutdown.

The CS52015-3 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.

The output or compensation capacitor helps determine

three main characteristics of a linear regulator: start-up

delay, load transient response and loop stability.

The capacitor value and type are based on cost, availabili-

ty, size and temperature constraints. A tantalum or alu-

minum 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 solu-

tion. However, when the circuit operates at low tempera-

tures, both the value and ESR of the capacitor will vary

considerably. The capacitor manufacturersÕ data sheet pro-

vides this information.

A 22µF tantalum capacitor will work for most applications,

but with high current regulators such as the CS52015-3 the

transient response and stability improve with higher val-

ues of capacitance. The majority of applications for this

regulator involve large changes in load current so the out-

put capacitor must supply the instantaneous load current.

The ESR of the output capacitor causes an immediate drop

in output voltage given by:

ÆV = ÆI

´ ESR

For microprocessor applications it is customary to use an

output capacitor network consisting of several tantalum and

ceramic capacitors in parallel. This reduces the overall ESR

and reduces the instantaneous output voltage drop under

load transient conditions. The output capacitor network

should be as close as possible to the load for the best results.

When large external capacitors are used with a linear regu-

lator it is sometimes necessary to add protection diodes. If

the input voltage of the regulator gets shorted, the output

capacitor will discharge into the output of the regulator.

The discharge current depends on the value of the capaci-

tor, the output voltage and the rate at which VIN drops. In

the CS52015-3 linear regulator, the discharge path is

through a large junction and protection diodes are not usu-

ally needed. If the regulator is used with large values of

output capacitance and the input voltage is instantaneous-

ly shorted to ground, damage can occur. In this case, a

diode connected as shown in Figure 1 is recommended.

Figure 1: Protection diode scheme for large output capacitors.

Since the CS52015-3 is a three terminal regulator, it is not

possible to provide true remote load sensing. Load regula-

tion is limited by the resistance of the conductors connect-

ing the regulator to the load. For best results the regulator

should be connected as shown in Figure 2.

Output Voltage Sensing

VOUT

VIN

CS52015-3

VIN

Gnd

VOUT

IN4002

(optional)

Protection Diodes

Stability Considerations

Typical Performance Characteristics

750

-100

100

200

Time

1500

-200

COUT =CIN =22mF Tantalum

Transient Response

Load Regulation vs. Output Current

0.025

0.000

0.050

0.075

0.100

Output Current (A)

CASE = 0°C

CASE = 125°C

CASE = 25°C

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