MAX6766 MAXIM [Maxim Integrated Products], MAX6766 Datasheet - Page 16

• Manufacturer Part Number: MAX6766
• Description: Automotive Micropower Linear Regulators with Supervisor
• Manufacturer: MAXIM [Maxim Integrated Products]

Automotive Micropower Linear Regulators
with Supervisor
Table 3. ENABLE/HOLD Truth Table/State Table
The MAX6773/MAX6774 include a watchdog timer that
asserts RESET if the watchdog input (WDI) does not
toggle within the watchdog timeout period t
typ). RESET remains low for the reset timeout period,
t
of time, the reset output appears as a pulse train,
asserted for the reset timeout period and deasserted
for the watchdog timeout period, until WDI is toggled
again. When RESET asserts, it stays low for the entire
reset timeout period ignoring any WDI transitions. To
prevent the watchdog from asserting RESET, toggle
WDI with a valid rising or falling edge prior to t
= 1.12s. The watchdog counter clears when WDI tog-
gles prior to t
resumes counting after RESET deasserts. The watch-
dog timer cannot be disabled.
When the junction temperature exceeds T
(typ), an internal thermal sensor signals the shutdown
logic that turns off the pass transistor and allows the IC
to cool. The thermal sensor turns the pass transistor on
again after the IC’s junction temperature cools by 20°C
(typ), resulting in a cycled output during continuous
thermal-overload conditions. Thermal protection pro-
tects the MAX6765–MAX6774 in the event of a fault con-
dition. Never exceed the absolute maximum junction
temperature rating of T
for the safe operating area.
The MAX6767–MAX6774 feature dual-mode operation:
these devices operate in either a preset or adjustable
16
RP
Initial State
Turn-On State
Hold
Setup State
Hold State
Off-State
OPERATING
. If the watchdog is not updated for lengthy periods
STATE
______________________________________________________________________________________
Watchdog Timer (MAX6773/MAX6774)
WD
Applications Information
ENABLE
or when RESET asserts. The watchdog
High
High
Low
Low
Low
J
Output Voltage Selection
= +150°C. See Figures 3 and 4
(floats high)
Don’t care
Don’t care
HOLD
High
Low
Low
Thermal Protection
REGULATOR
OUTPUT
J
Off
On
On
On
Off
= +160°C
WD
WD
(1.6s,
(min)
ENABLE is pulled to GND through an internal pulldown. HOLD is
floating (pulled up to OUT). Regulator output is disabled.
ENABLE is externally driven high turning the regulator output on.
HOLD is pulled up by OUT.
HOLD is externally pulled low while ENABLE remains high (latches
HOLD state).
ENABLE is driven low (or allowed to float low by an internal pulldown).
HOLD remains externally pulled low keeping the regulator output on.
HOLD is driven high (or allowed to float high by an internal pullup)
while ENABLE is low. Regulator output is shut off and ENABLE/
HOLD logic returns to the initial state.
voltage mode. In preset voltage mode, internal trimmed
feedback resistors set the internal linear regulator to
+1.8V, +2.5V, +3.3V, or +5V (see Table 2). Select pre-
set-voltage mode by connecting SET to ground. In
adjustable mode, select an output voltage between
+1.8V and +11V using two external resistors connected
as a voltage-divider to SET (see Figure 1). Set the out-
put voltage using the following equation:
where V
R2 is 50kΩ (maximum 100kΩ).
The MAX6769/MAX6770 feature an adjustable reset
threshold to monitor the voltage on RESETIN using a
resistive divider between the monitored voltage,
RESETIN and GND. See Figure 2. Use the following for-
mula to set the desired reset threshold:
where V
1.147V for L/T/Z/W versions.
Figure 2. RESETIN Threshold Selection
SET
TH
= 1.233V and the recommended value for
is 1.085V for the M/S/Y/V versions and
V
V
R3
R4
OUT
MON
V
RESETIN Threshold Selection
MON
COMMENT
= V
= V
RESETIN
SET
TH
MAX6769
MAX6770
(1 + R3 / R4)
(1 + R1 / R2)
GND
V
IN
IN
RESET