sp791 Exar Corporation, sp791 Datasheet - Page 11

• Manufacturer Part Number: sp791
• Description: Low Power Microprocessor Supervisory With Battery Switch-over
• Manufacturer: Exar Corporation

SP791DS/08
Figure 7. Reset and Chip-Enable Timing
The 10ns maximum CE propagation from CE
IN
most Ps.
CHIP-ENABLE INPUT
CE
RESET is asserted.
During a power-down sequence where V
below 4.65V, CE IN assumes a high impedance
state when the voltage at CE
15 s after RESET is asserted, whichever
occurs first, (Figure 7).
During a power-up sequence, CE
high impedance until RESET is deasserted.
In the high-impedance mode, the leakage
currents into this input are less than 1 A over
temperature. In the low-impedance mode, the
impedance of CE
in series with the load at CE
The propagation delay through the CE
transmission gate depends on both the source
impedance of the drive to CE
capacitive loading on CE
Enable Propagation Delay vs. CE
to CE
IN
THRESHOLD
is high impedance (disabled mode) while
OUT
CE
RESET
RESET
CE
Vcc
enables the SP791 to be used with
OUT
IN
IN
SP791 Low Power Microprocessor Supervisory with Battery Switch-Over
appears as a 65
OUT
OUT
IN
100 s
(see the Chip-
.
goes high or
15 s
IN
IN
OUT
and the
remains
resistor
CC
Load
falls
11
Capacitance graph in the Typical Operating
Characteristics). The CE propagation delay is
defined from the 50% point on CE
point on CE
load capacitance as in Figure 8. For minimum
propagation delay, minimize the capacitive load
at CE
driver.
CHIP-ENABLE OUTPUT
In the enabled mode, the impedance of CE
is equivalent to 65
driving CE
transmission gate is off and CE
pulled to V
transmission gate is enabled.
Figure 8. CE Propagation Delay Test Circuit
50 Driver
100 s
OUT
OUT
IN
and use a low output-impedance
OUT
. In the disabled mode, the 65
. This source turns off when the
using a 50 driver with 50pF
CE
in series with the source
© Copyright 2000 Sipex Corporation
IN
+5V
Vcc
GND
Corporation
CE
OUT
OUT
IN
to the 50%
is actively
50pF
C
LOAD
OUT