AAT1152
850kHz 1A Buck DC/DC Converter
Enable
2V/div
VOUT
1V/div
IL
0.5A/div
Time (200μs/div)
Figure 1: Inrush Limit (VIN = 3.6V; VOUT = 1.5V; IL = 1A).
Current Limit and Over-Temperature
Power and Signal Source
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 (shown in
schematic Figures 3 and 4) filters the noise associ-
ated with power switching.
For overload conditions, the peak input current is
limited. Figure 2 displays the current limit charac-
teristics. 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.
3.5
VCC = VP = 5.0V
3
VO = 3.3V
2.5
2
1.5
VCC = VP = 3.6V
VO = 1.5V
1
0.5
0
0
0.5
1
1.5
2
2.5
Output Current (A)
Figure 2: Current Limit Characteristics.
10
1152.2006.09.1.7
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
