MAX14720 Datasheet, PDF(14/38 Page) Maxim Integrated Products

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MAX14720 Datasheet, PDF (14/38 Pages) Maxim Integrated Products – Extended System Battery Use Time

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MAX14720/MAX14750

Power-Management Solution

Detailed Description

Power Regulation

The MAX14720/MAX14750 include a buck-boost regulator,

a synchronous buck regulator, a low quiescent current

linear regulator, and a power switch with integrated battery

monitoring. Burst mode operation of the switching regulators

provides excellent light-load efficiency and allows the

switching regulators to run continuously without significant

energy cost.

The buck-boost regulator in the devices is suitable for

applications (such as low-power display biasing) that

need the voltage present continuously while running from

a battery. The buck-boost regulator can also operate in a

current-limited mode to reduce current surges to the supply.

The current-limiting is implemented by dividing down the

frequency of the switching and is dependent on the ratio

of the input-to-output voltage. Step-down operation is not

allowed when current-limiting is active.

UVLO

In addition to the internal power-on reset (POR) circuit,

the devices also have two UVLO circuits that monitor the

voltages on BIN and LIN pin to ensure that input voltages are

sufficient for proper operation. It is required that the boost

and buck-boost are powered from the same voltage so they

share a UVLO on the BIN pin. The LDO has its own UVLO

on the LIN pin. The UVLO circuits are disabled when the

blocks are not enabled to reduce the quiescent current. The

devices provide the ability to select which of the two UVLOs

are used so that applications with BIN and LIN tied to the

same supply can share a single UVLO to reduce quiescent

current. The selection is made in the UVLOCfg register and

the effects of the different settings are shown in the Table 1.

In the MAX14720, if there is a fault in a block that is

enabled by the sequencer (every _Seq[2:0] option except

000, 110 or 111) the part will transition to the shutdown

and then the off state. The part will remain off until the

next button press. After the button press it will wait for the

fault to clear before beginning the power on sequence.

A fault is any condition that causes the block to turn off

when it should be enabled, such as a UVLO condition or

thermal shutdown.

Output Discharge

The regulators include circuitry to discharge their outputs.

Active discharge applies a current sink, while passive

discharge applies a load resistor. The active discharge is

enabled during hard reset, or for 10ms as the part enters

the off/seal mode. It can also be activated in the on state

by a register bit when the regulator is disabled. Passive

discharge is applied in the off/seal mode if the GlbPasDsc

bit is set and can also be applied in the on state by a

Power On/Off and Reset Control

The MAX14750 provides individual enable pins for each

of the primary functions, while the MAX14720 includes a

push-button monitor and sequencing controller. Figure 1

shows the basic flow diagram for the power-management

control inside the MAX14720. Each primary function

of the MAX14720 can be automatically enabled by the

sequencing controller. The functions can default to be

controlled by the I2C configuration registers. The default

state is determined by the factory configuration. See I2C

POWER

SEQUENCING

tRST DELAY

KIN = 0 > 10s, OR I2C CMD

MAX14720

SHUTDOWN HOLD

RST LOW ACTIVELY

DISCHARGE OUTPUTS

10ms DELAY

POWER-ON RESET

tBOOT DELAY

OFF

(SEAL MODE )

OTP

KIN = 0 > 400ms

Figure 1. Power State Diagram for MAX14720

Table 1. UVLO Configuration

UVLOCfg

0x00

0x01

0x02

0x03

BBBUVLOsel

LIN

BIN

LDOUVLOsel

LIN

BIN

LIN

BIN

BIN UVLO

Disabled

Enabled

LIN UVLO

Enabled

Disabled

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