Datasheet

TPS3820-xx-Q1, TPS3823-xx-Q1, TPS3824-xx-Q1, TPS3825-xx-Q1, TPS3828-xx-Q1
PROCESSOR SUPERVISORY CIRCUITS
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SGLS143B − DECEMBER 2002 − REVISED JUNE 2008
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description (continued)
During power-on, RESET is asserted when supply voltage V
DD
becomes higher than 1.1 V. Thereafter, the
supply voltage supervisor monitors V
DD
and keeps RESET active as long as V
DD
remains below the threshold
voltage V
IT−
. An internal timer delays the return of the output to the inactive state (high) to ensure proper system
reset. The delay time, t
d
, starts after V
DD
has risen above the threshold voltage V
IT−
. When the supply voltage
drops below the threshold voltage V
IT−
, the output becomes active (low) again. No external components are
required. All the devices of this family have a fixed-sense threshold voltage V
IT−
set by an internal voltage
divider.
The TPS3820/3/5/8 devices incorporate a manual reset input, MR
. A low level at MR causes RESET to become
active. The TPS3824/5 devices include a high-level output RESET. TPS3820/3/4/8 have a watchdog timer that
is periodically triggered by a positive or negative transition at WDI. When the supervising system fails to retrigger
the watchdog circuit within the time-out interval, t
tout
, RESET becomes active for the time period t
d
. This event
also reinitializes the watchdog timer. Leaving WDI unconnected disables the watchdog.
In applications where the input to the WDI pin may be active (transitioning high and low) when the
TPS3820/3/4/8 is asserting RESET
, the TPS3820/3/4/8 does not return to a non-reset state when the input
voltage is above Vt. If the application requires that input to WDI is active when RESET
is asserted, WDI must
be decoupled from the active signal. This can be accomplished by using an N-channel FET in series with the
WDI pin, with the gate of the FET connected to the RESET
output as shown in Figure 1.
WDI
RESET
TPS3824
WDI External
Figure 1
The product spectrum is designed for supply voltages of 2.5 V, 3 V, 3.3 V, and 5 V. The circuits are available
in a 5-pin SOT23-5 package. The TPS382x-xxQ devices are characterized for operation over a temperature
range of −40°C to 125°C, and are qualified in accordance with AEC-Q100 stress test qualification for integrated
circuits.