AS1374

Datasheet - Detailed Descr i pti on

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Revision 1.8

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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

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

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.

Trimmable

Reference

Bandgap

+

-

+

-

Enable Logic

CH1

Thermal

Protection

Common

Logic

Enable Logic

CH2

EN1

VIN

EN2

OUT1

GND

OUT2

AS1374

Overcurrent

Protection CH1

Overcurrent

Protection CH2