Datasheet

MAX814/MAX815/MAX816
±1% Accuracy, Low-Power, +3V and +5V
µP Supervisory Circuits
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_______________Detailed Description
The MAX814/MAX815/MAX816 are high-accuracy, low-
power microprocessor (µP) supervisory circuits. They
have µP-reset, watchdog-timer, and power-fail func-
tions. Typical applications illustrating their similarities
and differences are shown in Figures 1, 2, and 3.
Figures 4, 5, and 6 show the block diagrams of these
parts.
______________________________________________________________Pin Description
PIN
MAX814 MAX815 MAX816
NAME FUNCTION
1 1 1 MR
Manual-Reset Input. Triggers a reset when pulled below 1.10V. This active-
low input has an internal 150µA pullup current to V
CC
, and can be driven
with CMOS logic or shorted to GND with a switch or transistor.
2 2 —
Positive Power-Supply Input. When V
CC
is below the reset threshold
voltage*, RESET
is low, and remains low for a minimum of 140ms after
it rises above the threshold.
— — 2
V
CC
Positive Power-Supply Input. On the MAX816, RESET is controlled by
RESET IN, not V
CC
.
3 3 3 GND Ground
4 4 4 PFI
Power-Fail Input. The PFI threshold voltage is 1.70V on the MAX816 and on
MAX814/MAX815 parts with the T suffix. It is 2.50V on MAX814/MAX815
parts with K, L, and N suffixes. Connect PFI to GND or V
CC
when not used.
5 5 5 PFO
Power-Fail Output. When PFI is below its threshold, PFO is low;
otherwise it is high.
— 6 — WDI
Watchdog CMOS Input. If WDI remains high or low for more than 1.56s, the
watchdog timer times out, and WDO goes low. The timer is reset to
zero on each WDI transition.
6 — — LOW LINE
Low-Line Output. Normally high, LOW LINE goes low when V
CC
falls 60mV
above the reset threshold. It returns high as soon as V
CC
rises above the
low-line threshold.
— — 6 RESET IN
Reset Comparator Input. Reference is 1.70V. When RESET IN is below
1.70V, RESET is low, and remains low for a minimum of 140ms after it rises
above the reference.
7 7 7 RESET
Reset Output. Normally high, active low. Controlled by MR and reset
comparator.
8 — 8 RESET Reset Output. Active high. The inverse of RESET
.
— 8 — WDO
Watchdog Output. Normally high, WDO goes low whenever the V
CC
reset
threshold comparator input voltage is low or when the watchdog timer
times out. There is no appreciable delay going either direction when the
V
CC
threshold comparator toggles.
*Reset Threshold Voltage is determined by part number suffix: K = 4.80V, L = 4.70V, N = 4.55V, T = 3.03V.