AS1358 / AS1359
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1358 / AS1359 are ultra-low-noise, low-dropout, low-quiescent current linear-regulators specifically designed for space-limited
applications. The devices are available with preset output voltages from 1.5V to 4.5V in 50mV increments.
These devices can supply loads up to 150mA / 300mA. As shown in
Figure 18,
the AS1358 / AS1359 consist of an integrated bandgap core and
noise bypass circuitry, error amplifier, P-channel MOSFET pass transistor, and internal feedback voltage-divider.
Figure 18
shows the block diagram of the AS1358 / AS1359. It identifies the basics of a series linear regulator employing a 0.5 (typ) P-Channel
MOSFET as the control element. A stable voltage reference (REF in
Figure 18)
is compared with an attenuated sample of the output voltage.
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.
The AS1358 / AS1359 deliver preset output voltages from 1.5V to 4.5V, in 50mV increments
(see Ordering Information on page 15).
The output voltage is fed back through an internal resistor voltage-divider connected to pin OUT. An external bypass capacitor connected to pin
BYPASS reduces noise at the output. Startup time is minimized by internal power-on circuitry which pre-charges C
include a current limiter, thermal sensor, and shutdown logic.
Figure 18. AS1358 / AS1359 Block Diagram
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Noise Bypass
AS1358 /
AS1359
Revision 1.5
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AMSCO [ AUSTRIAMICROSYSTEMS AG ]
