MAX8734 Maxim Integrated Products, MAX8734 Datasheet - Page 23

• Manufacturer Part Number: MAX8734
• Description: (MAX8732 - MAX8734) Main Power-Supply Controllers
• Manufacturer: Maxim Integrated Products

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Drive SHDN below the precise SHDN input falling-edge
trip level to place the MAX8732/MAX8733/MAX8734
in their low-power shutdown state. The MAX8732/
MAX8733/MAX8734 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 discharged
to 0.3V through a 12Ω switch before entering True
Shutdown™. The accurate 1V falling-edge threshold on
SHDN can be used to detect a specific analog voltage
Table 3. Operating-Mode Truth Table
Table 4. Power-Up Sequencing
True Shutdown is a trademark of Maxim Integrated Products, Inc.
Thermal Shutdown
“> 2.4” => High
“> 2.4” => High
“> 2.4” => High
“> 2.4” => High
“> 2.4” => High
“> 2.4” => High
Undervoltage
Overvoltage
Discharge
Power-Up
Protection
Protection
Shutdown
SHDN
Standby
MODE
Low
(V)
Run
Supply Controllers for Notebook Computers
High-Efficiency, Quad-Output, Main Power-
______________________________________________________________________________________
V
High
High
High
REF
Low
Low
ON3
(V)
LDO5 < UVLO threshold
SHDN = high, ON3 or ON5
enabled
Either output > 111% of
nominal level, PRO = low
Either output < 70% of
nominal after 22ms time-
out expires and output is
enabled, PRO = low
PRO is low and either
SMPS output is still high in
either standby mode or
shutdown mode
ON5, ON3 < startup
threshold, SHDN = high
SHDN = low
T
X
J
> +160°C
CONDITION
V
High
High
High
Low
Low
REF
(V)
ON5
X
Shutdown Mode
LDO5
Off
On
On
On
On
On
On
On (after REF powers up)
On (after REF powers up)
On (after REF powers up)
On (after REF powers up)
On (after REF powers up)
On (after REF powers up)
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.
Normal operation
DL_ is forced high. LDO3, LDO5 active. Exited by a V+ POR or by toggling
SHDN, ON3, or ON5.
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 switch (12 ) 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.
DL_ stays high if PRO is low. LDO3, LDO5 active.
All circuitry off
All circuitry off. Exited by V+ POR or cycling SHDN, ON3, or ON5.
LDO3
Off
level and shut down the device. Once in shutdown, the
1.6V rising-edge threshold activates, providing sufficient
hysteresis for most applications. For additional hystere-
sis, the undervoltage threshold can be made dependent
on REF or LDO_, which go to 0V in shutdown.
ON3 and ON5 control SMPS power-up sequencing.
ON3 or ON5 rising above 2.4V enables the respective
outputs. ON3 or ON5 falling below 1.6V disables the
respective outputs.
Connecting ON3 or ON5 to REF forces the respective
outputs off while the other output is below regulation and
On (after 3V SMPS is up)
5V SMPS
COMMENT
Off
Off
On
Off
On
On
On/Off Controls (ON3, ON5)
Power-Up Sequencing and
On (after 5V SMPS is up)
3V SMPS
Off
Off
On
On
Off
On
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