MAX16016PTBS+T Maxim Integrated Products, MAX16016PTBS+T Datasheet - Page 15

• Manufacturer Part Number: MAX16016PTBS+T
• Description: IC UP SUPERVISOR LP 10TDFN-EP
• Manufacturer: Maxim Integrated Products
• Type: Battery Backup Circuitr

Specifications of MAX16016PTBS+T

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 145 ms Minimum
• Voltage - Threshold: 2.93V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TDFN Exposed Pad
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The watchdog monitors µP activity through the input
WDI. If the µP becomes inactive, either the reset output is
asserted in pulses (MAX16016) or the watchdog output
goes low (MAX16020/MAX16021). To use the watchdog
function, connect WDI to a bus line or µP I/O line. If WDI
remains high or low for longer than the watchdog timeout
period, the internal watchdog timer runs out and RESET
asserts for the reset timeout period (MAX16016) or WDO
goes low (MAX16020/MAX16021). The internal watchdog
timer clears whenever the reset output asserts or the
WDI sees a rising or falling edge within the watchdog
timeout period. The WDI input is designed for a three-
stated output device with a 10µA maximum leakage cur-
rent and the capability of driving a maximum capacitive
load of 200pF. The three-state device must be able to
source and sink at least 200µA when active. Disable the
watchdog timer by leaving WDI unconnected or by
three-stating the driver connected to WDI. The watchdog
timer periodically attempts to pulse WDI to the opposite
logic-level through a 25kΩ resistor for 40µs to determine
whether WDI is either unconnected or latched to a logic
state. The watchdog function is also disabled when in
battery-backup mode.
WDO remains high if there is a transition or pulse at WDI
during the watchdog-timeout period. WDO goes low if no
transition occurs at WDI during the watchdog timeout
period and remains low until the next transition at WDI or
when a reset is asserted. Connect WDO to MR to gener-
ate a system reset on every watchdog fault. When a
Figure 1. Watchdog Timing (MAX16016/MAX16020)
Battery-Backup Circuit and Chip-Enable Gating
WDO
WDI
______________________________________________________________________________________
Low-Power µP Supervisory Circuits with
Watchdog Timer
Watchdog Output
Watchdog Input
t
WD
watchdog fault occurs in this mode, WDO goes low,
which pulls MR low, causing a reset pulse to be issued.
As soon as the reset output is asserted, the watchdog
timer clears and WDO returns high. With WDO connect-
ed to MR, a continuous high or low on WDI causes
145ms (min) reset pulses to be issued every 1.235s.
The MAX16020/MAX16021 feature a battery testing
function that works in conjunction with the BATTOK out-
put. The battery voltage is tested for 1.235s after V
applied and once every 24 hours thereafter. During this
test, an internal 100kΩ resistor is connected from BATT
to ground and the battery is monitored to ensure that
the battery voltage is above 2.6V. If the battery voltage
is below 2.6V, the BATTOK output deasserts low to indi-
cate a weak battery condition. The MAX16020 has a
BATT_TEST output that pulses high during the battery
voltage test. Connect a resistor and FET as shown in
Figure 6 to provide an additional load during the battery
test. In battery-backup mode, the battery testing function
is disabled and BATTOK goes low.
The MAX16016/MAX16020/MAX16021 battery fresh-
ness seal disconnects the backup battery from internal
circuitry and OUT until V
backup battery connected to BATT is fresh when the
final product is used for the first time.
The internal freshness seal latch prevents BATT from
powering OUT until V
setting the latch. When V
BATT begins to power OUT.
t
WD
Battery Testing Function/BATTOK
Indicator (MAX16020/MAX16021)
Battery Freshness Seal Mode
CC
t
CC
WD
has come up for the first time,
CC
is applied. This ensures the
subsequently turns off,
CC
15
is