MAX77720 datasheet(32/52 Pages) AD

32 / 52 page

Wide Output-Voltage Range, Dual-

Polarity PMIC

MAX77720

www.analog.com

Analog Devices | 32

Calculate the value of RTOP (from VFBBST to VOUTBST) for a desired VOUTBST at startup with the following equation:

�� = �� (

��

− 1)

Where:

• VOUTBST is the desired positive output voltage

• VFBBST is the default internal reference voltage at the FBBST pin, 1.25V (typ)

For best accuracy, set RBOT to a value smaller than 475kΩ to ensure that the current flowing through it is significantly

larger than the FBBST pin bias current. The advantage of using a higher value for RBOT is the reduction of quiescent

current for achieving the highest efficiency at light load currents. However, using RBOT values that are lower increases

immunity against noise injection. Additionally, using one percent tolerance resistors (or better) are recommended to

maintain high output-voltage accuracy.

Figure 12 shows a small circuit diagram of the feedback network.

PGNDBST

VOUTBST

FBBST

AGND

RTOP

RBOT

Figure 12. Connecting External Feedback Network

Detailed Description—Two-Wire Communication

General Description

The MAX77720 uses a 2-wire bus system to communicate by standard I2C protocol. The target address used by the host

to access the IC determines what memory locations are available to read or write.

System Configuration

The 2-wire bus system supporter operation as a target-only device in a single or multitarget, and single or multicontroller

system. Using a 7-bit target address, the system can support up to 128 target addresses. The 2-wire interface consists

of a serial data line (SDA) and serial clock line (SCL). SDA and SCL provide bidirectional communication between the IC

and a controller device at speeds up to 1MHz.

TARGET

TRANSMITTER/

RECEIVER

TARGET

TRANSMITTER

TARGET

RECEIVER

CONTROLLER

TRANSMITTER/

RECEIVER

CONTROLLER

TRANSMITTER/

RECEIVER

SDA

SCL

Figure 13. Functional Logic Diagram for the Communications Controller

MAX77720 Datasheet(PDF) 32 Page - Analog Devices

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