X40430_06 Datasheet, PDF (9/26 Pages) Intersil Corporation – Triple Voltage Monitor with Integrated CPU Supervisor

X40430, X40431, X40434, X40435
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 neces-
sary 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, fol-
lowed 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 operation. To
check if the V_TRIPX has been set, set VXMON to a value
slightly greater than V_TRIPX (that was previously set).
Slowly ramp down VXMON and observe when the corre-
sponding 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.
CONTROL REGISTER
The Control Register provides the user a mechanism
for changing the Block Lock and Watchdog Timer set-
tings. The Block Lock and Watchdog Timer bits are
nonvolatile and do not change when power is removed.
The Control Register is accessed with a special pream-
ble in the slave byte (1011) and is located at address
1FFh. It can only be modified by performing a byte write
operation directly to the address of the register and only
one data byte is allowed for each register write opera-
tion. Prior to writing to the Control Register, the WEL
and RWEL bits must be set using a two step process,
with the whole sequence requiring 3 steps. See "Writing
to the Control Registers" on page 11.
The user must issue a stop, after sending this byte to
the register, to initiate the nonvolatile cycle that stores
WD1, WD0, PUP1, PUP0, and BP. The X40430,
X40431, X40434, X40435 will not acknowledge any
data bytes written after the first byte is entered.
The state of the Control Register can be read at any
time by performing a random read at address 1FFh,
using the special preamble. Only one byte is read by
each register read operation. The master should
supply a stop condition to be consistent with the bus
protocol.
7
6
5
4
PUP1 WD1 WD0 BP
3
2
1
0
0 RWEL WEL PUP0
RWEL: Register Write Enable Latch (Volatile)
The RWEL bit must be set to “1” prior to a write to the
Control Register.
9
FN8251.1
May 24, 2006