9

Pin Descriptions

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

minimum of 2.2

µF, low ESR capacitor to GND for stable

operation.

Bypass with 2.2

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

µF, 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

µF, 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.

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

the RESET threshold.

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

output stage of the integrated reset supervisory circuit. The

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

(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

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

threshold, keeping it asserted for a programmable time (set

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

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

transients/glitches.

ISL6414