AAT1152
850kHz 1A Synchronous Buck DC/DC Converter
Enable
2V/div
VOUT
1V/div
IL
0.5A/div
VIN=3.6V
VOUT=1.5V
IL=1A
200µsec/div
Figure 1: Inrush Limit
Power and Signal Source
Current Limit and Over-temperature
protection
Separate small signal ground and power supply
pins isolate the internal control circuitry from the
noise associated with the output MOSFET switch-
ing. The low pass filter R1 and C3 in schematic fig-
ures 3 and 4 filters the noise associated with the
power switching.
For overload conditions the peak input current is
limited. Figure 2 displays the VI current limit char-
acteristics. As load impedance decreases and the
output voltage falls closer to zero, more power is
dissipated internally, raising the device tempera-
ture. Thermal protection completely disables
switching when internal dissipation becomes
excessive, protecting the device from damage. The
junction over-temperature threshold is 140°C with
15°C of hysteresis.
Current Limit Characteristic
3.5
3
VCC =VP = 5.0V
VO = 3.3V
2.5
2
Figure 4 schematic
1.5
1
VCC =VP =3.6V
VO = 1.5V
Figure 3 schematic
0.5
0
0
0.5
1
1.5
2
2.5
IOUT (A)
Figure 2.
10
1152.2003.01.0.9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
