MAX8734A datasheet(23/33 Pages) MAXIM

部品番号	MAX8734A

部品情報	High-Efficiency, Quad-Output, Main Power-Supply Controllers for Notebook Computers

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メーカー	MAXIM [Maxim Integrated Products]

ホームページ	https://www.maximintegrated.com/en.html

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23 / 33 page

High-Efficiency, Quad-Output, Main Power-

Supply Controllers for Notebook Computers

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23

synchronous rectifier drivers clamp the SMPS outputs

to GND. When PRO is high, the SMPS outputs do not

discharge and the DL_ synchronous rectifier drivers

remain low.

Shutdown Mode

Drive SHDN below the precise SHDN input falling-edge

trip level to place the MAX8732A/MAX8733A/MAX8734A

in their low-power shutdown state. The MAX8732A/

MAX8733A/MAX8734A consume only 6µA of quiescent

current while in shutdown mode. When shutdown mode

activates, the reference turns off, making the threshold

to exit shutdown inaccurate. To guarantee startup,

drive SHDN above 2V (SHDN input rising-edge trip

level). For automatic shutdown and startup, connect

SHDN to V+. If PRO is low, both SMPS outputs are dis-

charged to 0.3V through a 12

Ω switch before entering

true shutdown. The accurate 1V falling-edge threshold

on SHDN can be used to detect a specific analog volt-

age level and shut down the device. Once in shutdown,

the 1.6V rising-edge threshold activates, providing suffi-

cient hysteresis for most applications. For additional

hysteresis, the undervoltage threshold can be made

dependent on REF or LDO_, which go to 0V in shutdown.

MODE

CONDITION

COMMENT

Power-Up

LDO5 < UVLO threshold

Transitions to discharge mode after a V+ POR and after REF becomes valid.

LDO5, LDO3, and REF remain active. DL_ is active if PRO is low.

Run

SHDN = high, ON3 or ON5

enabled

Normal operation.

Overvoltage

Protection

Either output > 111% of

nominal level, PRO = low

DL_ is forced high. LDO3, LDO5 active. Exited by a V+ POR or by toggling

SHDN, ON3, or ON5.

Undervoltage

Protection

Either output < 70% of

nominal after 22ms time-

out expires and output is

enabled, PRO = low

If PRO is low, DL_ is forced high after discharge mode terminates. LDO3,

LDO5 active. Exited by a V+ POR or by toggling SHDN, ON3, or ON5.

Discharge

PRO is low and either

SMPS output is still high in

either standby mode or

shutdown mode

Discharge switch (12

Ω) connects OUT_ to PGND. One output may still run

while the other is in discharge mode. Activates when LDO_ is in UVLO, or

transition to UVLO, standby, or shutdown has begun. LDO3, LDO5 active.

Standby

ON5, ON3 < startup

threshold, SHDN = high

DL_ stays high if PRO is low. LDO3, LDO5 active.

Shutdown

SHDN = low

All circuitry off.

Thermal Shutdown

TJ > +160°C

All circuitry off. Exited by V+ POR or cycling SHDN, ON3, or ON5.

Table 3. Operating-Mode Truth Table

SHDN

(V)

VON3

(V)

VON5

(V)

LDO5

LDO3

5V SMPS

3V SMPS

Low

X

Off

“> 2.4” => High

Low

On

On (after REF powers up)

Off

“> 2.4” => High

High

On

On (after REF powers up)

On

“> 2.4” => High

High

Low

On

On (after REF powers up)

Off

On

“> 2.4” => High

Low

High

On

On (after REF powers up)

On

Off

“> 2.4” => High

High

REF

On

On (after REF powers up)

On (after 3V SMPS is up)

On

“> 2.4” => High

REF

High

On

On (after REF powers up)

On

On (after 5V SMPS is up)

Table 4. Power-Up Sequencing

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