AS1374
Datasheet - Detailed Description
8 Detailed Description
Figure 25 shows the block diagram of the AS1374. It identifies the basics of a series linear regulator employing a P-Channel MOSFET as the
control element. A stable voltage reference (REF in Figure 25) is compared with an attenuated sample of the output voltage. Any difference
between the two voltages (reference and sample) creates an output from the error amplifier that drives the series control element to reduce the
difference to a minimum. The error amplifier incorporates additional buffering to drive the relatively large gate capacitance of the series pass P-
channel MOSFET, when additional drive current is required under transient conditions. Input supply variations are absorbed by the series
element, and output voltage variations with loading are absorbed by the low output impedance of the regulator.
8.1 Output Voltage
The AS1374 deliver preset output voltages from 1.2V to 3.6V, in 50mV increments (see Ordering Information on page 17).
8.2 Enable
The AS1374 feature an active high enable mode to shutdown each output independently. Driving EN 1 low disables Output 1, driving EN 2 low
disables Output 2. The disabled Output enters a high-impedance state.
Figure 25. AS1374 Block Diagram
-
+
EN1
VIN
Enable Logic
CH1
OUT1
GND
Overcurrent
Protection CH1
Thermal
Protection
Common
Logic
Trimmable
Reference
Bandgap
Overcurrent
Protection CH2
Enable Logic
CH2
EN2
OUT2
+
-
AS1374
8.3 Current Limit
The AS1374 include a current limiting circuitry to monitor and control the P-channel MOSFET pass transistor’s gate voltage, thus limiting the
device output current to 300mA.
Note: See Table 3 on page 4 for the recommended min and max current limits. The output can be shorted to ground indefinitely without
causing damage to the device.
8.4 Thermal Protection
Integrated thermal protection circuitry limits total power dissipation in the AS1374. When the junction temperature (TJ) exceeds +160ºC, the
thermal sensor signals the shutdown logic, turning off the P-channel MOSFET pass transistor and allowing the device to cool down. The thermal
sensor turns the pass transistor on again after the device’s junction temperature drops by 15ºC, resulting in a pulsed output during continuous
thermal-overload conditions.
Note: Thermal protection is designed to protect the devices in the event of fault conditions. For continuous operation, do not exceed the
absolute maximum junction temperature rating of +150ºC.
www.austriamicrosystems.com/LDOs/AS1374
Revision 1.8
9 - 18
AMSCO [ AMS(艾迈斯) ]
