8

Pin Descriptions

PVCC - Positive supply for the power (internal FET) stage of

the PWM section.

SGND - Analog ground for the PWM. All internal control

circuits are referenced to this pin.

EN _PWM- The PWM controller is enabled when this pin is

HIGH, and held off when the pin is pulled LOW. It is a CMOS

EN_LDO - LDO1 and LDO2 are enabled when this pin is

HIGH, and held off when the pin is pulled LOW. It is a CMOS

CT - Timing capacitor connection to set the 25ms minimum

pulse width for the RESET/RESET signal.

RESET, RESET - These complementary pins are the

The IC asserts these RESET and RESET signals whenever

the supply voltage drops below a preset threshold; keeping

above the reset threshold. These outputs are push-pull.

RESET is LOW when re-setting the microprocessor. The

UVLO threshold.

PG_LDO - This is a high impedance open drain output that

provides the status of both LDOs. When either of the outputs

are out of regulation, PG_LDO goes LOW.

CC1 - This is the compensation capacitor connection for

LDO1. Connect a 0.033µF capacitor from CC1 to

GND_LDO.

CC2 - This is the compensation capacitor connection for

LDO2. Connect a 0.033µF capacitor from CC2 to

GND_LDO.

low ESR capacitor to GND_LDO for stable operation.

GND_LDO - Ground pin for LDO1 and LDO2.

low ESR capacitor to GND_LDO for stable operation.

PGND - Power ground for the PWM controller stage.

converter stage. For fixed 1.8V operation, connect this pin

directly to the output voltage.

PG_PWM - This pin is an active pull-up/pull-down able to

PG_PWM - This pin provides an inverted PG_PWM output.

LX - The LX pin is the switching node of synchronous buck

converter, connected internally at the junction point of the

upper MOSFET source and lower MOSFET drain. Connect

this pin to the output inductor.

stage and must be closely decoupled to ground.

SYNC - This is the external clock synchronization input. The

device can be synchronized to 500kHz to 1MHz switching

frequency.

GND - Tie this pin to the ground plane with a low impedance,

shortest possible path.

Functional Description

The ISL6413 is a 3-in-1 multi-output regulator designed for

wireless chipset power applications. The device integrates a

single synchronous buck regulator with dual LDOs. It

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

The 1.8V is generated using a synchronous buck regulator

with greater then 92% efficiency. Both 2.84V supplies are

generated from ultra low noise LDO Regulators. Under

voltage lock-out (UVLO) prevents the converter from turning

on when the input voltage is less then typically 2.6V

Additional blocks include an output over-current protections,

thermal sensor, PGOOD detectors, RESET function and

shutdown logic.

Synchronous Buck Regulator

The Synchronous buck regulator with integrated N- and

P-channel power MOSFET provides pre-set 1.8V for

BBP/MAC core supply. Synchronous rectification with

internal MOSFETs is used to achieve higher efficiency and

reduced number of external components. Operating

frequency is typically 750kHz allowing the use of smaller

inductor and capacitor values. The device can be

synchronized to an external clock signal in the range of

500kHz to 1MHz. The PG_PWM output indicates loss of

regulation on PWM output.

The PWM architecture uses a peak current mode control

scheme with internal slope compensation. At the beginning

of each clock cycle, the high side P-channel MOSFET is

turned on. The current in the inductor ramps up and is

sensed via an internal circuit. The error amplifier sets the

threshold for the PWM comparator. The high side switch is

turned off when the sensed inductor current reaches this

threshold. After a minimum dead time preventing shoot

through current, the low side N-channel MOSFET will be

turned on and the current ramps down again. As the clock

cycle is completed, the low side switch will be turned off and

the next clock cycle starts.

The control loop is internally compensated reducing the

amount of external components. The PWM section includes

an anti-ringing switch to reduce noise at light loads.

The switch current is internally sensed and the minimum

current limit is 600mA.

ISL6413