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AS1340

Datasheet - Application In form atio n

9.7 Capacitor Selection

A 4.7µF capacitor is recommended for CIN as well as a 2µF for COUT. Small-sized ceramic capacitors are recommended. X5R and X7R

ceramic capacitors are recommend as they retain capacitance over wide ranges of voltages and temperatures.

9.7.1 Output Capacitor Selection

Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since they have extremely low

ESR and are available in small footprints. A 2.2 to 10µF output capacitor is sufficient for most applications. Larger values up to 22µF may be

used to obtain extremely low output voltage ripple and improve transient response.

X5R and X7R dielectric materials are recommended due to their ability to maintain capacitance over wide voltage and temperature ranges.

9.7.2 Input Capacitor Selection

Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Ceramic capacitors are

recommended for input decoupling and should be located as close to the device as is practical. A 4.7µF input capacitor is sufficient for most

applications. Larger values may be used without limitations.

9.7.3 Diode Selection

A Schottky diode must be used to carry the output current for the time it takes the PMOS synchronous rectifier to switch on.

Note:

Do not use ordinary rectifier diodes, since the slow recovery times will compromise efficiency.

9.8 Thermal Protection

To protect the device from short circuit or excessive power dissipation of the auxiliary NPNs, the integrated thermal protection switches off the

device when the junction temperature (TJ) reaches 145ºC (typ). When TJ decreases to approximately 125ºC, the device will resume normal

operation. If the thermal overload condition is not corrected, the device will switch on and off while maintaining TJ within the range between

125ºC and 145ºC.

Table 5. Recommended Output Capacitor

Part Number

C

TC Code

Rated Voltage

Dimensions (L/W/T)

Manufacturer

GRM31MR71H105KA88

1µF

X7R

50V

C1206

Murata

www.murata.com

GRM32ER71H475KA88

4.7µF

X7R

50V

C1210

C1206C105K5RAC

1µF

X7R

50V

C1206

Kemet

www.kemet.com

C1206C225K5RAC

2.2µF

X7R

50V

C1210

1206C105KAT2A

1µF

X7R

50V

C1206

AVX

www.avx.com

Table 6. Recommended Input Capacitor

Part Number

C

TC Code

Rated Voltage

Dimensions (L/W/T)

Manufacturer

GRM21BR71C105KA01

1µF

X7R

16V

C0805

Murata

www.murata.com

GRM21BR61C225KA88

2.2µF

X7R

16V

C0805

GRM32DR71C106KA01

10µF

X7R

16V

C1210

Table 7. Recommended Diodes

Part Number

Reverse Voltage

Forward Current

Package

Manufacturer

PMEG4010BEA

40V

1A

SOD123

Philips

www.nxp.com

MBR0540

40V

500mA

SOD123

MCC

www.mccsemi.com

MBR0560

60V

500mA

SOD123