ILC705 Impala Linear Corporation, ILC705 Datasheet - Page 4

• Manufacturer Part Number: ILC705
• Description: MP SUPERVISORY CIRCUIT
• Manufacturer: Impala Linear Corporation

Microprocessor Reset
The RESET pin is asserted whenever V
reset threshold voltage or when MR goes low. The reset pin
remains asserted for a period of 200ms after V
above the reset threshold voltage and MR goes high. The
reset function ensures the microprocessor is properly reset
and powers up into a known condition after a power failure.
RESET will remain valid with V
The microprocessor can be monitored by connecting the
WDI pin (watchdog input) to a bus line or I/O line. If a tran-
sition does not occur on the WDI pin within the watchdog
timeout period, then WDO will go low. A minimum pulse of
50ns or any transition low-to-high or high-to-low on the WDI
pin will reset the watchdog timer. The output of the watch-
dog timer (WDO) will remain high if WDI sees a valid tran-
sition within the watchdog timeout period or if WDI is left
floating. If V
WDO goes low immediately regardless of WDI. If WDI is left
floating, then WDO can be used as a low line indicator.
Manual Reset
The manual-reset input (MR) allows reset to be triggered by
a pushbutton switch which is debounced by the 140ms min-
imum reset pulse width. MR can be driven by external
TTL/CMOS compatible logic. By connecting WDO to MR a
watchdog timeout will generate a reset pulse in the
ILC705/ILC706.
Power Fail Warning
An additional comparator which is independent of other
functions on the ILC705/706/707/708 is provided for early
warning of power failure. An external voltage divider can be
used to compare unregulated DC to an internal 1.25V ref-
erence. The voltage divider ratio on the input of the power
ILC705-708 1.0
Circuit Description
Watchdog Timer
mP Supervisory Circuit
RESET
Impala Linear Corporation
WDO
V
MR
CC
t
MD
CC
falls below the reset threshold voltage then
t
MR
t
RS
CC
as low as 1.4V
V
RT
CC
falls below the
[phone]
t
RS
CC
has risen
fail comparator (PFI) can be chosen so as to trip the power
fail comparator a few milliseconds before V
the maximum reset threshold voltage. The output of the
power fail comparator (PFO) can be used to interrupt the
microprocessor when used in this mode and execute shut-
down procedures prior to power loss
www.impalalinear.com
Unregulated DC
Alternate Reference Guide
R1
R2
PFI
MAX705CPA
MAX705CSA
MAX705EPA
MAX705ESA
ADM705AN
DS1705
MAX706CPA
MAX706CSA
MAX706EPA
MAX706C/D
ADM706AN
DS1706
MAX707CPA
MAX707CSA
MAX707EPA
MAX707ESA
MAX707C/D
ADM707AN
DS1707
MAX708CPA
MAX708CSA
MAX708EPA
MAX708ESA
MAX708C/D
ADM708AN
DS1708
Industry P/N
4
1.25 V
ILC705N
ILC705M
ILC705N
ILC705M
ILC705N
ILC705
ILC706N
ILC706M
ILC706N
ILC706D
ILC706N
ILC706
ILC707N
ILC707M
ILC707N
ILC707M
ILC707D
ILC707N
ILC707
ILC708N
ILC708M
ILC708N
ILC708M
ILC708D
ILC708N
ILC708
Replacement
+
ILC Direct
-
Sept 1999
CC
5
falls below
PFO
4