SMS47
PreliminaryInformation
CONFIGURATION REGISTERS
If cascading is enabled, the designer must insure V0 is the
primary supply and is the first to become active.
SUPPLY AND MONITOR FUNCTIONS
TheV0, V1, V2, andV3 inputsareinternallydiode-ORedso
that any one of the four can act as the device supply. The
RESET# output will be guaranteed true so long as one of
the four pins is at or above 1V.
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.
Note: for performing a Read or Write to the con-
figuration register contents, at least one supply
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.
LocatethecapacitorsasphysicallyclosetotheSMS47as
possible.
If the value contained in any register is all zeroes, the
correspondingthresholdwillbe0.6V. Ifthecontentswere
lowrange 05HEX thethresholdwouldthenbe0.625V[0.6V
+ (5 × 0.005V)]. All four registers are configured as 8-Bit
registers.
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 AND THRESHOLD RANGE
conditiononV1. Whenthisconditionceases,theRESET#
output will remain active for tPRTO (programmable reset
time-out). This reset time-out interval takes priority over
the PUP outputs for use of the timer.
The reset output has four programmable sources for
activation. Configurationregister4isusedforselectingthe
activationsource(D7:4),whichcanbeanycombinationof
V0, V1, V2 and V3. A monitor input can be programmed to
activate on either an under-voltage or over-voltage condi-
tion. The low-order four bits of configuration register 5
programtheseoptions. Theresetthresholdvoltagerange
for V0 to V3 can be set for 5mV increments below 1.875V
(lowRange="0")orfor15mVincrementsabove1.8V(high
range = "1") using Bits D3:0.
TheRESET#outputhastwohardwiredsourcesforactiva-
tion: the MR# input, and the expiration of the Watchdog
timer. RESET# will remain active so long as MR# is low,
and will continue driving the RESET# output for tPRTO
(programmableresettimeout)afterMR#returnshigh. The
MR# input cannot be bypassed or disabled.
TheRESET#outputwillbecomeactivewhentriggeredby
a selected activation source such as an under-voltage
Refer to Figures 2, 3 and 4 for a detailed illustration of the
relationships among the affected signals.
D7
D0
D6
D5
D4
D3
D2
D1
Action
MSB
LSB
X
X
X
X
V3
V2
V1
V0
Thestatusofthefoursuppliesisavailableatanytimeover
theI2Cbusinthehighorderconfigurationbitsofregister5
(Table 3). A "1" in a bit location indicates a fault on that
supply.
Voltage Threshold Range
Select
Low
RESET Trigger Enable
0
0
0
0
Range
High
1
1
1
1
Range
Table 2. Configuration Register 4
SUMMIT MICROELECTRONICS, Inc.
2087 1.1 04/11/05
10
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
