SMS48
PreliminaryInformation
DEVICE OPERATION AND CONFIGURATION REGISTERS
Associatedwitheachinputisacomparatorwithaprogram-
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 V0, V1, V2,
and V3 respectively.
SUPPLY AND MONITOR FUNCTIONS
The V0, V1, V2, and V3 inputs are internally ORed so that
any one of the four can act as the device supply. The
RESET#outputswillbeguaranteedtruesolongasoneof
the four pins is at or above 1V.
Note:forperformingaReadorWriteoperationand
tohavetheabilitytochangeconfigurationregister
contents at least one supply input must be above
2.7V.
If the value contained in any register is all zeroes, the
correspondingthresholdwillbe0.6V. Ifthecontentswere
lowrange05HEX thethresholdwouldthenbe0.625V[0.6V
+ (5 × 0.005V)]. All four registers are configured as 8-Bit
registers.
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.
LocatethecapacitorsasphysicallyclosetotheSMS48 as
possible.
D7
D0
D6
D5
D4
D3
D2
D1
Action
MSB
LSB
Highest threshold adjustment = 5.625V
1
1
1
1
1
1
1
1
(High Range)
Lowest threshold adjustment = 0.6V
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
(Low Range)
0
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. Configurationregister4isusedforenablingthe
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,
eachindividualRESET#outputwillremainactivefortPRTO
(programmableresettime-out).Theresetthresholdvoltage
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.
RESET# outputs will remain active so long as MR# is low,
and will continue driving the RESET# outputs for tPRTO
(programmableresettimeout)afterMR#returnshigh. 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 SMS48 provides the option of the monitors triggering
on either an under-voltage or over-voltage condition. The
low-orderfourbitsofconfigurationregister5programthese
options.
The RESET#0-3 outputs have two hardwired sources for
activation: the MR# input and Watchdog timer. All
WATCHDOG TIMER
D7
D0
D6
D5
D4
D3
D2
D1
Action
MSB
LSB
The SMS48 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#.
X
X
X
X
V3
V2
V1
V0
Voltage Threshold Range
Select
Low
If the watchdog should time-out the device status can be
monitored in the status register (Table 4). Refer to Figure
3whichillustratestheactionofRESET#0-3withrespectto
the Watchdog timer and the WLDI input.
RESET Trigger Enable
0
1
0
1
0
1
0
1
Range
High
Range
Table 2. Configuration Register 4
SUMMIT MICROELECTRONICS, Inc.
2088 1.1 04/10/05
8
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
