SMS46
Preliminary Information
DEVICE OPERATION AND CONFIGURATION REGISTERS
SUPPLY AND MONITOR FUNCTIONS
The V
0
, V
1
, V
2,
and V
3
inputs are internally ORed so that
any one of the four can act as the device supply. The
RESET# outputs will be guaranteed true so long as one of
the four pins is at or above 1V.
Note:
for performing a memory operation (Read
or Write) and to have the ability to change
configuration register contents at least one sup-
ply input must be above 2.7V.
Read/Write operations require a 0.1µF capacitor from the
VDD_CAP node to GND. For optimum performance
connect capacitors from each of the Vx inputs to GND.
Locate the capacitors as physically close to the SMS46 as
possible.
Associated with each input is a comparator with a program-
mable threshold for detection of under-voltage or over-
voltage conditions on any of the four supply inputs. The
threshold can be programmed in 5mV increments any-
where within the range of 0.6V to 1.875V or 15mV incre-
ments within the range of 1.8V to 5.625V. Configuration
registers 0, 1, 2, and 3 adjust the thresholds for V
0
, V
1
, V
2,
and V
3
respectively.
If the value contained in any register is all zeroes, the
corresponding threshold will be 0.6V. If the contents were
low range 05
HEX
the threshold would then be 0.625V [0.6V
+ (5
×
0.005V)]. All four registers are configured as 8-Bit
registers.
D7
MSB
1
0
0
D6
1
0
0
D5
1
0
0
D4
1
0
0
D3
1
0
0
D2
1
0
1
D1
1
0
1
D0
LSB
1
0
0
Action
Highest threshold adjustment = 5.625V
(High Range)
Lowest threshold adjustment = 0.6V
(Low Range)
Threshold = 0.6V + (6
×
0.005V) = 0.625V
(e.g.)
Table 1. Configuration Registers 0, 1, 2, and 3
RESET# FUNCTION
Each RESET# output has a programmable source for
activation. Configuration register 4 is used for enabling the
activation source. A monitor input can be programmed to
activate on either an under-voltage or over-voltage condi-
tion, but not both conditions. When this condition ceases,
each individual RESET# output will remain active for t
PRTO
(programmable reset time-out). The reset threshold voltage
range for V0 to V3 can be set for 5mV increments below
1.875V (low Range = "0") or for 15mV increments above
1.8V (high range = "1") using Bits D3:0.
The RESET#0-3 outputs have two hardwired sources for
activation: the MR# input and Watchdog timer. All
D7
MSB
V
3
D6
V
2
D5
V
1
D4
V
0
D3
V
3
D2
V
2
D1
V
1
D0
LSB
V
0
Action
RESET# outputs will remain active so long as MR# is low,
and will continue driving the RESET# outputs for t
PRTO
(programmable reset time out) after MR# returns high. The
MR# input cannot be bypassed or disabled.
Refer to Figures 1, 2 and 3 for a detailed illustration of the
relationships among the affected signals.
The SMS46 provides the option of the monitors triggering
on either an under-voltage or over-voltage condition. The
low-order four bits of configuration register 5 program these
options.
WATCHDOG TIMER
The SMS46 contains an independent timer that can be
programmed. The Watchdog generates all RESET#s if it
times out. The timer is cleared by a low to high transition
on WLDI and will reset all four RESET#.
If the watchdog should time-out the device status can be
monitored in the status register (Table 4). Refer to Figure
3 which illustrates the action of RESET#0-3 with respect to
the Watchdog timer and the WLDI input.
Voltage Threshold Range
Select
RESET Trigger Enable
0
1
0
1
0
1
0
1
Low
Range
High
Range
Table 2. Configuration Register 4
8
2083 1.1 06/04/04
SUMMIT MICROELECTRONICS, Inc.
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
