X40030_06 Datasheet, PDF (8/24 Pages) Intersil Corporation – Triple Voltage Monitor with Integrated CPU Supervisor

X40030, X40031, X40034, X40035
WATCHDOG TIMER
The Watchdog Timer circuit monitors the microproces-
sor activity by monitoring the SDA and SCL pins. A
standard read or write sequence to any slave address
byte restarts the watchdog timer and prevents the
WDO signal going active. A minimum sequence to
reset the watchdog timer requires four microprocessor
instructions namely, a Start, Clock Low, Clock High
and Stop. The state of two nonvolatile control bits in
the Status Register determine the watchdog timer
period. The microprocessor can change these watch-
dog bits by writing to the X40030, X40031, X40034,
X40035 control register (also refer to page 21).
Figure 4. Watchdog Restart
.6µs
1.3µs
SCL
SDA
Start
WDT Reset ^Stop
V1, V2 AND V3 THRESHOLD PROGRAM
PROCEDURE (OPTIONAL)
The X40030 is shipped with standard V1, V2 and V3
threshold (V_TRIP1, V_TRIP2, V_TRIP3) voltages. These
values will not change over normal operating and stor-
age conditions. However, in applications where the
standard thresholds are not exactly right, or if higher
precision is needed in the threshold value, the X40030,
X40031, X40034, X40035 trip points may be adjusted.
The procedure is described below, and uses the appli-
cation of a high voltage control signal.
Setting a V_TRIPx Voltage (x=1, 2, 3)
There are two procedures used to set the threshold
voltages (V_TRIPx), depending if the threshold voltage to
be stored is higher or lower than the present value. For
example, if the present V_TRIPx is 2.9 V and the new
V_TRIPx is 3.2 V, the new voltage can be stored directly
into the V_TRIPx cell. If however, the new setting is to be
lower than the present setting, then it is necessary to
“reset” the V_TRIPx voltage before setting the new value.
Setting a Higher V_TRIPx Voltage (x=1, 2, 3)
To set a V_TRIPx threshold to a new voltage which is
higher than the present threshold, the user must apply
the desired V_TRIPx threshold voltage to the corre-
sponding input pin (Vcc(V1MON), V2MON or V3MON).
Then, a programming voltage (Vp) must be applied to
the WDO pin before a START condition is set up on
SDA. Next, issue on the SDA pin the Slave Address
A0h, followed by the Byte Address 01h for V_TRIP1, 09h
for V_TRIP2, and 0Dh for V_TRIP3, and a 00h Data Byte in
order to program V_TRIPx. The STOP bit following a valid
write operation initiates the programming sequence. Pin
WDO must then be brought LOW to complete the oper-
ation. To check if the V_TRIPX has been set, set VXMON
to a value slightly greater than V_TRIPX (that was previ-
ously set). Slowly ramp down VXMON and observe
when the corresponding outputs (LOWLINE, V2FAIL
and V3FAIL) switch. The voltage at which this occurs is
the V_TRIPX (actual).
CASE A
Now if the desired V_TRIPX is greater than the V_TRIPX
(actual), then add the difference between V_TRIPX
(desired) – V_TRIPX (actual) to the original V_TRIPX
desired. This is your new V_TRIPX that should be
applied to VXMON and the whole sequence should be
repeated again (see Figure 5).
CASE B
Now if the V_TRIPX (actual), is higher than the V_TRIPX
(desired), perform the reset sequence as described in
the next section. The new V_TRIPX voltage to be applied
to VXMON will now be: V_TRIPX (desired) – (V_TRIPX
(actual) – V_TRIPX (desired)).
Note: This operation does not corrupt the memory array.
Setting a Lower V_TRIPx Voltage (x=1, 2, 3)
In order to set V_TRIPx to a lower voltage than the
present value, then V_TRIPx must first be “reset” accord-
ing to the procedure described below. Once V_TRIPx
has been “reset”, then V_TRIPx can be set to the desired
voltage using the procedure described in “Setting a
Higher V_TRIPx Voltage”.
Resetting the V_TRIPx Voltage
To reset a V_TRIPx voltage, apply the programming volt-
age (Vp) to the WDO pin before a START condition is
set up on SDA. Next, issue on the SDA pin the Slave
Address A0h followed by the Byte Address 03h for
V_TRIP1, 0Bh for V_TRIP2, and 0Fh for V_TRIP3, followed
by 00h for the Data Byte in order to reset V_TRIPx. The
STOP bit following a valid write operation initiates the
programming sequence. Pin WDO must then be
brought LOW to complete the operation.
After being reset, the value of V_TRIPx becomes a nomi-
nal value of 1.7V or lesser.
Notes: 1.This operation does not corrupt the memory
array.
2. Set V_CC ≅ 1.5(V2MON or V3MON), when
setting V_TRIP2 or V_TRIP3 respectively
8
FN8114.1
May 25, 2006