MAX77816 datasheet(11/26 Pages) MAXIM

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Output Voltage Slew-Rate Control

Buck-Boost regulator supports programmable slew-rate

control feature when increasing and decreasing the out-

put voltage. The ramp-up slew-rate can be set to 20mV/µs

or 40mV/µs through BB_RU_SR bit, while the ramp-down

slew-rate is programmable to 5mV/µs or 10mV/µs through

BB_RD_SR bit.

Output Active Discharge

Buck-boost provides an internal 100Ω resistor for output

active discharge function. If the active discharge function

is enabled (BB_AD = 1), the internal resistor discharges

the energy stored in the output capacitor to PGNDBB

whenever the regulator is disabled.

Either the regulator remains enabled or the active dis-

charge function is disabled (BB_AD = 0), the internal

resistor is disconnected from the output. If the active dis-

charge function is disabled, the output voltage decays at a

rate that is determined by the output capacitance and the

load current when the regulator is turned off.

Inductor Selection

Buck-boost is optimized for a 1µH inductor. The lower the

inductor DCR, the higher buck-boost efficiency is. Users

need to trade off inductor size with DCR value and choose

a suitable inductor for buck-boost.

Input Capacitor Selection

The input capacitor, CIN, reduces the current peaks

drawn from the battery or input power source and reduces

switching noise in the device. The impedance of CIN at

the switching frequency should be kept very low. Ceramic

capacitors with X5R or X7R dielectrics are highly rec-

ommended due to their small size, low ESR, and small

temperature coefficients. For most applications, a 10µF

capacitor is sufficient.

Output Capacitor Selection

The output capacitor, COUT, is required to keep the

output voltage ripple small and to ensure regulation loop

stability. COUT must have low impedance at the switch-

ing frequency. Ceramic capacitors with X5R or X7R

dielectric are highly recommended due to their small size,

low ESR, and small temperature coefficients. For stable

operation, buck-boost requires 16µF of minimum effective

output capacitance. Considering DC bias characteristic

of ceramic capacitors, a 47µF 6.3V capacitor is recom-

mended for most of applications.

Serial Interface

I2C-compatible 2-wire serial interface is used for regulator

on/off control, setting output voltages, and other functions.

Refer to the Register Map section for details.

I2C serial bus consists of a bidirectional serial-data line

(SDA) and a serial clock (SCL). I2C is an open-drain bus.

SDA and SCL require pullup resistors (500Ω or greater).

Optional 24Ω resistors in series with SDA and SCL help

to protect the device inputs from high voltage spikes on

the bus lines. Series resistors also minimize crosstalk and

undershoot on bus lines.

System Configuration

I2C bus is a multimaster bus. The maximum number of

devices that can attach to the bus is only limited by bus

capacitance.

Figure 6 shows an example of a typical I2C system. A

device on I2C bus that sends data to the bus in called a

transmitter. A device that receives data from the bus is

called a receiver. The device that initiates a data transfer

and generates SCL clock signals to control the data trans-

fer is a master. Any device that is being addressed by

the master is considered a slave. When MAX77816 I2C

compatible interface is operating, it is a slave on I2C bus

and it can be both a transmitter and a receiver.

Bit Transfer

One data bit is transferred for each SCL clock cycle. The

data on SDA must remain stable during the high portion of

SCL clock pulse. Changes in SDA while SCL is high are

control signals (START and STOP conditions).

Table 2. Suggested Inductors for Buck-Boost

MANUFACTURER

SERIES

NOMINAL

INDUCTANCE

(µH)

RESISTANCE

(typ) (mΩ)

CURRENT

RATING (A)

-30% (∆L/L)

CURRENT

RATING (A)

∆T = -40°C RISE

DIMENSIONS

L x W x H (mm)

TDK

TFM201610GHM-

1R0MTAA

1.0

3.8

3.0

2.0 x 1.6 x 1.0

TOKO

DFE322512C

1.0

4.6

3.7

3.2 x 2.5 x 1.2

Coilcraft

XAL4020-102MEB

1.0

8.7

9.6

4.0 x 4.0 x 2.1

MAX77816

High-Efficiency Buck-Boost Regulator

with 5A Switches

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