X9522_06 Datasheet, PDF (14/27 Pages) Intersil Corporation – Triple DCP, Dual Voltage Monitors

X9522
Setting a Higher V_TRIPx Voltage (x = 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 (V2 or V3). Then, a programming
voltage (Vp) must be applied to the WP 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 09h for V_TRIP3, 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 program-
ming sequence. Pin WP must then be brought LOW to
complete the operation (See Figure 16). The user
does not have to set the WEL bit in the CONSTAT reg-
ister before performing this write sequence.
Setting a Lower V_TRIPx Voltage (x = 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 WP 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 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 fol-
lowing a valid write operation initiates the program-
ming sequence. Pin WP must then be brought LOW to
complete the operation (See Figure 16).The user does
not have to set the WEL bit in the CONSTAT register
before performing this write sequence.
After being reset, the value of V_TRIPx becomes a nomi-
nal value of 1.7V.
V_TRIPx Accuracy (x = 2,3)
The accuracy with which the V_TRIPx thresholds are set,
can be controlled using the iterative process shown in
Figure 17.
If the desired threshold is less that the present threshold
voltage, then it must first be “reset” (See "Resetting the
VTRIPx Voltage").
The desired threshold voltage is then applied to the
appropriate input pin (V2 or V3) and the procedure
described in Section “Setting a Higher V_TRIPx Voltage“
must be followed.
Once the desired V_TRIPx threshold has been set, the
error between the desired and (new) actual set threshold
can be determined. This is achieved by applying Vcc / V1
to the device, and then applying a test voltage higher
than the desired threshold voltage, to the input pin of the
voltage monitor circuit whose V_TRIPx was programmed.
For example, if V_TRIP2 was set to a desired level of 3.0 V,
then a test voltage of 3.4 V may be applied to the voltage
monitor input pin V2. In all cases, care should be taken
not to exceed the maximum input voltage limits.
After applying the test voltage to the voltage monitor
input pin, the test voltage can be decreased (either in dis-
crete steps, or continuously) until the output of the volt-
age monitor circuit changes state. At this point, the error
between the actual / measured, and desired threshold
levels is calculated.
For example, the desired threshold for V_TRIP2 is set to
3.0 V, and a test voltage of 3.4 V was applied to the input
pin V2 (after applying power to Vcc / V1). The input volt-
age is decreased, and found to trip the associated output
level of pin V2RO from a LOW to a HIGH, when V2
reaches 3.09 V. From this, it can be calculated that the
programming error is 3.09 - 3.0 = 0.09 V.
If the error between the desired and measured V_TRIPx is
less than the maximum desired error, then the program-
ming process may be terminated. If however, the error is
greater than the maximum desired error, then another
iteration of the V_TRIPx programming sequence can be
performed (using the calculated error) in order to further
increase the accuracy of the threshold voltage.
If the calculated error is greater than zero, then the
V_TRIPx must first be “reset”, and then programmed to the
a value equal to the previously set V_TRIPx minus the cal-
culated error. If it is the case that the error is less than
zero, then the V_TRIPx must be programmed to a value
equal to the previously set V_TRIPx plus the absolute value
of the calculated error.
Continuing the previous example, we see that the calcu-
lated error was 0.09V. Since this is greater than zero, we
must first “reset” the V_TRIP2 threshold, then apply a volt-
age equal to the last previously programmed voltage,
minus the last previously calculated error. Therefore, we
must apply V_TRIP1 = 2.91 V to pin V2 and execute the
programming sequence (See "Setting a Higher VTRIPx
Voltage (x = 2,3)" ) .
Using this process, the desired accuracy for a particu-
lar V_TRIPx threshold may be attained using a succes-
sive number of iterations.
14
FN8208.1
January 3, 2006