www.ams.com/DC-DC_Step-Up

Revision 1.12

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AS1312

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9.1.2

Thermal Shutdown

To prevent the AS1312 from short-term misuse and overload conditions the chip includes a thermal overload protection. To block the normal

junction temperature exceeds 150°C. To resume the normal operation the temperature has to drop below 140°C.

A good thermal path has to be provided to dissipate the heat generated within the package. Otherwise it’s not possible to operate the AS1312 at

its usable maximal power. To dissipate as much heat as possible from the package into a copper plane with as much area as possible, it’s

recommended to use multiple vias in the printed circuit board. It’s also recommended to solder the Exposed Pad (pin 9) to the GND plane.

Note:

Continuing operation in thermal overload conditions may damage the device and is considered bad practice.

9.2 Component Selection

Only four components are required to complete the design of the step-up converter. The low peak currents of the AS1312 allow the use of low

value, low profile inductors and tiny external ceramic capacitors.

9.3 Inductor Selection

For best efficiency, choose an inductor with high frequency core material, such as ferrite, to reduce core losses. The inductor should have low

DCR (DC resistance) to reduce the I²R losses, and must be able to handle the peak inductor current without saturating. A 6.8µH inductor with a

> 500mA current rating and < 500m

Ω DCR is recommended.

9.4 Capacitor Selection

The convertor requires three capacitors. Ceramic X5R or X7R types will minimize ESL and ESR while maintaining capacitance at rated voltage

for a list of capacitors for input and output capacitor selection.

On the pin REF a 100nF capacitor with an Insulation resistance >1G

Ω is recommended.

Table 4. Recommended Inductors

Part Number

L

DCR

Current Rating

Dimensions (L/W/T)

Manufacturer

XPL2010-682M

6.8µH

421m

Ω

0.62A

2.0x1.9x1.0mm

Coilcraft

www.coilcraft.com

EPL2014-682M

6.8µH

287m

Ω

0.59A

2.0x2.0x1.4mm

LPS3015-682M

6.8µH

300m

Ω

0.86A

3.0x3.0x1.5mm

LPS3314-682M

6.8µH

240m

Ω

0.9A

3.3x3.3x1.3mm

LPS4018-682M

6.8µH

150m

Ω

1.3A

3.9x3.9x1.7mm

LQH32CN6R8M53L

6.8µH

250m

Ω

0.54A

3.2x2.5x1.55mm

Murata

www.murata.com

LQH3NPN6R8NJ0L

6.8µH

210m

Ω

0.7A

3.0x3.0x1.1mm

LQH44PN6R8MJ0L

6.8µH

143m

Ω

0.72A

4.0x4.0x1.1mm

Table 5. Recommended Input and Output Capacitors

Part Number

C

TC Code

Rated Voltage

Dimensions (L/W/T)

Manufacturer

GRM21BR60J226ME99

22µF

X5R

6.3V

0805, T=1.25mm

Murata

www.murata.com

GRM31CR61C226KE15

22µF

X5R

16V

1206, T=1.6mm

GRM31CR60J475KA01

47µF

X5R

6.3V

1206, T=1.6mm

Table 6. Recommended Capacitors for REF

Part Number

C

TC Code

Insulation

Resistance

Rated

Voltage

Dimensions (L/W/T)

Manufacturer

GRM188R71C104KA01

100nF

X7R

>5G

Ω

16V

0603, T=0.8mm

Murata

www.murata.com