AS1312
Datasheet - Application Information
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
operation mode all further switching is inhibited for output voltage above VOUT lockout threshold. The device is in thermal shutdown when the
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 < 500mΩ DCR is recommended.
Table 4. Recommended Inductors
Part Number
L
DCR
Current Rating
0.62A
Dimensions (L/W/T)
2.0x1.9x1.0mm
2.0x2.0x1.4mm
3.0x3.0x1.5mm
3.3x3.3x1.3mm
3.9x3.9x1.7mm
3.2x2.5x1.55mm
3.0x3.0x1.1mm
4.0x4.0x1.1mm
Manufacturer
XPL2010-682M
EPL2014-682M
6.8µH
6.8µH
6.8µH
6.8µH
6.8µH
6.8µH
6.8µH
6.8µH
421m
287m
300m
240m
150m
250m
210m
143m
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
0.59A
Coilcraft
www.coilcraft.com
LPS3015-682M
0.86A
LPS3314-682M
0.9A
LPS4018-682M
1.3A
LQH32CN6R8M53L
LQH3NPN6R8NJ0L
LQH44PN6R8MJ0L
0.54A
Murata
www.murata.com
0.7A
0.72A
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
over temperature. The VIN capacitor should be 22µF. The VOUT capacitor should be between 22µF and 47µF. A larger output capacitor should
be used if lower peak to peak output voltage ripple is desired. A larger output capacitor will also improve load regulation on VOUT. See Table 5
for a list of capacitors for input and output capacitor selection.
Table 5. Recommended Input and Output Capacitors
Part Number
C
TC Code
X5R
Rated Voltage
6.3V
Dimensions (L/W/T)
0805, T=1.25mm
1206, T=1.6mm
Manufacturer
GRM21BR60J226ME99
GRM31CR61C226KE15
GRM31CR60J475KA01
22µF
22µF
47µF
Murata
www.murata.com
X5R
16V
X5R
6.3V
1206, T=1.6mm
On the pin REF a 100nF capacitor with an Insulation resistance >1GΩ is recommended.
Table 6. Recommended Capacitors for REF
Insulation
Resistance
Rated
Voltage
Part Number
C
TC Code
Dimensions (L/W/T)
Manufacturer
Murata
www.murata.com
GRM188R71C104KA01
100nF
X7R
>5GΩ
16V
0603, T=0.8mm
www.ams.com/DC-DC_Step-Up
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