MAX1153/MAX1154
Stand-Alone, 10-Channel, 10-Bit System Monitors
with Internal Temperature Sensor and VDD Monitor
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23
execute a manual conversion. See Figure 9 for manual
conversion timing:
1) Disable autoscan (set up register scan mode bit to
zero), if necessary.
2) Pull CS low.
3) Initiate a conversion by issuing a Manually
Triggered Conversion command (0000, followed by
the address bits of the channel to be converted).
4) Pull CS high to start the conversion.
5) Maintain a logic high on CS to allow for reference
power-up (if the reference mode requires it) and
conversion time.
6) Pull CS low.
7) Issue a Read Current Data Register for Selected-
Channel command (0010, followed by the same
address of the channel in the Manually Triggered
Conversion command).
Voltage Measurements
Every voltage measurement (internal VDD or external
input channel) requires 10.6s to complete. If the inter-
nal reference needs to power up (reference mode =
01), an additional 40s is required every time the
MAX1153/MAX1154 come out of automatic shutdown
mode after a sample wait period greater than 80s.
Monitoring VDD
This internal acquisition channel samples and converts
the supply voltage, VDD.
VDD value can be calculated from the digitized data
with the following equation:
The reference voltage must be larger than 1/2VDD for
the operation to work properly. VDD monitoring requires
10.6s (typ) per measurement.
Temperature Measurement
The MAX1153/MAX1154 perform temperature measure-
ment by measuring the voltage across a diode-con-
nected transistor at two different current levels. The
following equation illustrates the algorithm used for
temperature calculations:
temperature
V
x
HIGH
LOW
=
()
q
k
nx ln
I
High
LOW
V
x current data register content x
V
DD
REF
=
2
1024
(_
_
)
C3
C2
C1 C0
A2
A1
A0
SCLK
DIN
DOUT
C3
C2
C1 C0
A2
A1
A0
A3
CS
tPU+CONV
Figure 9. Manual Conversion Timing Without Reading Data