NCP57302, NCV57302

http://onsemi.com

8

APPLICATIONS INFORMATION

Output Capacitor and Stability

The NCP57302 device requires an output capacitor for

stable operation. The NCP57302 is designed to operate with

ceramic output capacitors. The recommended output

capacitance value is 47

mF or greater. Such capacitors help

to improve transient response and noise reduction at high

frequency.

Input Capacitor

An input capacitor of 1.0

mF or greater is recommended

when the device is more than 4 inches away from the bulk

supply capacitance, or when the supply is a battery. Small,

surface−mount chip capacitors can be used for the

bypassing. The capacitor should be place within 1 inch of

the device for optimal performance. Larger values will help

to improve ripple rejection by bypassing the input of the

regulator, further improving the integrity of the output

voltage.

Minimum Load Current

The NCP57302 regulator is specified between finite

loads. A 10 mA minimum load current is necessary for

proper operation.

Enable Input

NCP57302 regulators also feature an enable input for

on/off control of the device. It’s shutdown state draws “zero”

current from input voltage supply (only microamperes of

leakage). The enable input is TTL/CMOS compatible for

Overcurrent and Reverse Output Current Protection

The NCP57302 regulator is fully protected from damage

due to output current overload and output short conditions.

When NCP57302 output is overloaded, Output Current

limiting is provided. This limiting is linear; output current

during overload or output short conditions is constant. These

features are advantageous for powering FPGAs and other

ICs having current consumption higher than nominal during

their startup.

Thermal shutdown disables the NCP57302 device when

the die temperature exceeds the maximum safe operating

temperature.

difference is less than 6.5 V in the application, the output

structure of these regulators is able to withstand output

voltage (backup battery as example) to be applied without

reverse current flow.

Adjustable Voltage Design

The NCP/NCV57302 Adjustable voltage Device Output

voltage is set by the ratio of two external resistors as shown

in Figure 21.

The device maintains the voltage at the ADJ pin at 1.24 V

referenced to ground. The current in R2 is then equal to

1.24 V / R2, and the current in R1 is the current in R2 plus

the ADJ pin bias current. The ADJ pin bias current flows

Figure 21. Adjustable Voltage Operation

R1

R2

+

+

VIN

EN

VOUT

ADJ

GND

NCP57302

R1

R2

47 mF,

Ceramic

For the R2 resistor value up to 15 k

impact can be neglected and the R1 resistor value can be

calculated y:

R1 + R2

1.24

* 1

(eq. 1)

Thermal Considerations

The power handling capability of the device is limited by

total power dissipated by the device has two components,

Input to output voltage differential multiplied by Output

current and Input voltage multiplied by GND pin current.

The GND pin current value can be found in Electrical

Characteristics table and in Typical Characteristics graphs.

(eq. 3)

Ambient Thermal Resistance of the NCP/NCV57302

device mounted on the specific PCB.

To maximize efficiency of the application and minimize

thermal power dissipation of the device it is convenient to

use the Input to output voltage differential as low as possible.

The static typical dropout characteristics for various

output voltage and output current can be found in the Typical

Characteristics graphs.