MAX77179 Просмотр технического описания (PDF) - Maxim Integrated

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MAX77179

High-Bandwidth LTE/WCDMA PA Power Management ICs in a 1.75mm x 1.4mm, 0.4mm Pitch WLP

Maxim Integrated 

MAX77178 / MAX77179

High-Bandwidth LTE/WCDMA PA Power Management ICs

in a 1.75mm x 1.4mm, 0.4mm Pitch WLP

Pin Description (continued)

PIN

MAX77178 MAX77179

C1

—

—

C1

C2

C2

C3, C4

C3, C4

NAME

SEL1

BYP

PGND

IN2,

IN1

FUNCTION

Output-Voltage Selection Input 1. Connect SEL0 and SEL1 to logic-high or logic-low

to set the step-down converter output voltage to one of four voltage levels. See Table

1. SEL1 is internally connected to AGND through an 800kI pulldown resistor.

Bypass Mode Selection Input. When BYP = GND, the IC is set for automatic bypass

mode operation. When BYP = IN, the control circuitry forces the IC into bypass

mode where the high-side FET is turned on continuously with all FET scaling

segments enabled, regardless of the mode of operation. BYP is internally connected

to AGND through an 800kI pulldown resistor.

Power Ground. Connect PGND and the input/output capacitor grounds through a

star connection to the PCB ground plane.

Power-Supply Voltage Input. Connect IN1/IN2 to a battery or supply voltage from

2.5V to 5.5V. IN1/IN2 powers the internal p-channel and n-channel MOSFETs.

Bypass IN1/IN2 to PGND with a 4.7FF ceramic capacitor as close as possible to the

devices. Connect IN1/IN2 to the same source as IN3.

Detailed Description

The MAX77178/MAX77179 step-down converters are

optimized for dynamically powering the PA in multiband

3G/4G mobile communications. They provide a single-

device PA power-management solution that supports

basic power control for WCDMA and LTE applications.

The devices are high-bandwidth converters designed to

meet the load-transient response requirements for large-

signal polar transmitter architectures.

The MAX77178 provides two logic control inputs (SEL0

and SEL1) to program the DC-DC converter output volt-

age to one of four options (1.0V, 1.7V, 2.325V, or 2.9V).

This method simplifies system implementation by mini-

mizing changes to the existing baseband software. For

other output voltage options, contact factory.

The MAX77179 provides an independent DAC-controlled

analog input (REF) to support power control applications

for WCDMA/LTE. Two other logic control inputs (BYP and

MODE_SEL) select the DAC-controlled input source and

the ICs’ operational modes for multimode applications.

The output voltage range (0.5V to VIN) supports opera-

tion with a wide variety of PAs, and allows implementation

of aggressive power-management schemes.

The 2.5V to 5.5V input supply range supports both

current and future battery chemistries. Fast switching

frequency allows the use of small ceramic input and

output capacitors while maintaining low-ripple voltage.

Efficiency is enhanced at light loads by switching to

skip mode where the converter switches only as needed

to service the load when the skip mode is enabled.

Adaptive smart FET scaling further improves efficiency

under all operating conditions.

Shutdown Mode

Connect EN to AGND or logic-low to place the ICs in

shutdown mode. In shutdown, the control circuitry, inter-

nal switching MOSFET and synchronous rectifier turn off

and LX becomes high impedance. Connect EN to IN_, or

logic-high for normal operation.

SKIP Mode

The step-down converters feature skip mode to provide

the highest possible efficiency during light load condi-

tions. Skip mode is only activated when the output volt-

age is within 12% of the desired regulated value. This

requirement maintains the proper slew-rate operation

of the output voltage, particularly when the REF input

is slewing down. Skip mode occurs when a zero-cross

condition is detected on the inductor current.

Maxim Integrated

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