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AS1374

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

The AS1374 is an ultra-low-noise, low-dropout, low-quiescent current linear-regulator with two seperated outputs spe-

cifically designed for space-limited applications. These device can supply loads up to 200mA. As shown in Figure 25,

the AS1374 consist of an integrated bandgap core, error amplifier, P-channel MOSFET pass transistor, and internal

feedback voltage-divider.

The output voltage is fed back through an internal resistor voltage-divider connected to pin OUT. Additional blocks

include a current limiter, thermal sensor, and enable logic.

Internal Voltage Reference

The bandgap reference is connected to the error amplifier’s inverting input. The error amplifier compares this reference

with the feedback voltage and amplifies the difference. If the feedback voltage is lower than the reference voltage, the

pass-transistor gate is pulled low. This allows more current to pass to the output and increases the output voltage. If

the feedback voltage is too high, the pass transistor gate is pulled high, allowing less current to pass to the output.

Internal P-Channel Pass Transistor

The AS1374 feature a 0.6

Ω (typ) P-channel MOSFET pass transistor, which provides several advantages over similar

designs using a PNP pass transistor, including prolonged battery life. The P-channel MOSFET does not require a base

driver, thus quiescent current is dramatically reduced. The AS1374 do not exhibit problems associated with typical

PNP-based LDOs, and consume only 30µA of quiescent current in light load and 50µA in dropout (see Typical Operat-

ing Characteristics on page 5).

Output Voltage

The AS1374 deliver preset output voltages from 1.2V to 3.6V, in 50mV increments (see Ordering Information on page

13).

Enable

The AS1374 feature an actice high enable mode to shutdown each output indepentend. Driving EN 1 low disables Out-

put 1, driving EN 2 low disables Output 2. The disabled Output enters a high-impedance state.

Figure 25. AS1374 - Block Diagram

EN 1

GND

OUT 1

AS1374

-

+

OUT 2

-

+

Overcurrent

Protection CH2

Overcurrent

Protection CH1

Trimmable

Reference

Bandgap

Common

Logic

Enable Logic

CH2

Enable Logic

CH1

Thermal

Protection

EN 2

VDD