www.ams.com/DC-DC_Step-Up/AS1340 Revision 1.20 13 - 17
AS1340
Datasheet - Application Information
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 T
J 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
