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ISL6414

Triple Output, Low-Noise LDO Regulator with Integrated Reset Circuit

Renesas Electronics 

ISL6414

Pin Descriptions

OUT1 - This pin is the output for LDO1. Bypass with a

minimum of 2.2F, low ESR capacitor to GND for stable

operation.

VIN - Supply input pins. Connect to input power source.

Bypass with 2.2F capacitor to GND. Both VIN pins must be

tied together on the PC board, close to the IC.

GND - Ground pin for LDO1 and LDO2.

CC1 - Compensation Capacitor for LDO1. Connect a 0.033µF

capacitor from CC1 to GND.

SHDN - Shutdown input for LDO1 and LDO2. Connect to IN for

normal operation. Drive SHDN pin LOW to turn off LDO1 and

LDO2.

OUT2 - This pin is the output for LDO2. Bypass with a

minimum of 2.2F, low ESR capacitor to GND for stable

operation.

CT - Timing pin for the RESET circuit pulse width.

CC2 - Compensation capacitor for LDO2. Connect a 0.033µF

capacitor from CC2 to GND.

OUT3 - This pin is output for LDO3. Bypass with a minimum of

2.2F, low ESR capacitor to GND3 for stable operation.

GND3 - Ground pin for LDO3.

CC3 - Compensation capacitor for LDO3. Connect a 0.033µF

capacitor from CC3 to GND3.

SHDN3 - Shutdown input for LDO3. Connect to VIN for normal

operation. Drive SHDN3 pin LOW to turn off LDO3.

FAULT - This is the power good indicator for LDO1. When the

1.8V output is out of regulation (>±5%, typ.), this pin goes

LOW. This pin also goes LOW during thermal shutdown and

any overcurrent event on LDO1. Connect this pin to GND, if

unused. This pin remains HIGH in the shutdown mode, as

controlled by the SHDN pin (refer to Figure 19).

RESET - This pin is the active-LOW output of the push-pull

output stage of the integrated reset supervisory circuit. The

reset circuit monitors VIN and asserts a RESET output at this

pin, if VIN falls below the RESET threshold. The RESET output

remains LOW, while the VIN pin voltage is below the reset

threshold, and for at least 25ms, after VIN rises above the

RESET threshold.

RESET - This pin is the active-HIGH output of the push-pull

output stage of the integrated reset supervisory circuit. The

reset circuit monitors VIN and asserts a RESET output at this

pin, if VIN falls below the RESET threshold. The RESET output

remains HIGH, while the VIN pin voltage is below the RESET

threshold, and for at least 25ms, after VIN rises above the

RESET threshold.

Functional Description

The ISL6414 is a 3-in-1 multi-output, low dropout, regulator

designed for wireless chipset power applications. It supplies

three fixed output voltages 1.8V, 2.84V and 2.84V. The 1.8V

output from LDO1 remains active down to a VIN = 2.7V (min.),

ensuring proper BBP/MAC operation. Each LDO consists of a

1.2V reference, error amplifier, MOSFET driver, P-Channel

pass transistor, dual-mode comparator and internal feedback

voltage divider.

The 1.2V band gap reference is connected to the error

amplifier’s inverting input. The error amplifier compares this

reference to the selected feedback voltage and amplifies the

difference. The MOSFET driver reads the error signal and

applies the appropriate drive to the P-Channel pass transistor.

If the feedback voltage is lower then the reference voltage, the

pass transistor gate is pulled lower, allowing more current to

pass and increasing the output voltage. If the feedback voltage

is higher then the reference voltage, the pass transistor gate is

driven higher, allowing less current to pass to the output. The

output voltage is fed back through an internal resistor divider

connected to OUT1/2/3 pins.

Additional blocks include an output overcurrent protection,

reverse battery protection, thermal sensor, fault detector,

RESET function and shutdown logic.

Internal P-Channel Pass Transistors

The ISL6414 features a typical 0.5 rDS(ON) P-channel

MOSFET pass transistors. This provides several advantages

over similar designs using PNP bipolar pass transistors. The P-

Channel MOSFET requires no base drive, which reduces

quiescent current considerably. PNP based regulators waste

considerable current in dropout when the pass transistor

saturates. They also use high base drive currents under large

loads. The ISL6414 does not suffer from these problems.

Integrated RESET for MAC/ Baseband Processors

The ISL6414 includes a microprocessor supervisory block.

This block eliminates the extra RESET IC and external

components needed in wireless chipset applications. This

block performs a single function; it asserts a RESET signal

whenever the VIN supply voltage decreases below a preset

threshold, keeping it asserted for a programmable time (set by

external capacitor CT) after the VIN pin voltage has risen

above the RESET threshold.

The push pull output stage of the reset circuit provides both an

active-Low and an active-HIGH output. This function is

guaranteed to be in the correct state for VIN down to 1V. The

reset comparator is designed to ignore transients on the VIN

pin. The RESET threshold for ISL6414 is 2.63V typical.

In addition to issuing a reset to the microprocessor during

power-up, power down and brownout conditions, this block is

relatively immune to short duration, negative-going VIN

transients/glitches.

FN9128 Rev 1.00

Aug 2, 2004

Page 9 of 12

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