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MAX9949/MAX9950
Current-Range Selection
Three bits from the control word, RS0, RS1, RS2, con-
trol the full-scale current range for either FI (force cur-
rent) or MI (measure current). Table 6 describes the
full-scale current-range control.
Clamp Enable
The CLENABLE bit enables the force-output voltage
clamps when high and disables the clamps when low.
Table 7 depicts the various clamp mode options.
Measure Output High-Impedance Control
The MSR_ output attains a low-leakage, high-imped-
ance state by using the
HI-ZMSR control bit or the HI-Z_
input. The 2 bits are logically ORed together to control
the MSR_ output. The
HI-Z_ input allows external multi-
plexing among several PMU MSR_ outputs without
using the serial interface. Table 8 explains the various
output modes for the MSR_ output.
Digital Output (DOUT)
The digital output follows the last output of the serial
shift register and clocks out on the falling edge of the
input clock. DOUT provides the first bit of the incoming
serial data word 16.5 clock cycles later. This allows for
daisy-chaining an additional device using DOUT and
the same clock.
“Quick Load” Using Chip Select
If
CS goes low and then returns high without any clock
activity, the data from the input registers latch into the
PMU registers. This extra function is not standard for
SPI/QSPI/MICROWIRE interfaces. The quick load mim-
ics the function of
LOAD without forcing LOAD low.
Comparators
Two comparators configured as a window comparator
monitor the MSR_ output. THMAX_ and THMIN_ set the
high and low thresholds that determine the window.
Both outputs are open drain and share a single disable
control that places the outputs in a high-Z, low-leakage
state. Table 9 describes the comparator output states
of the MAX9949/MAX9950.
Dual Per-Pin Parametric Measurement Units
______________________________________________________________________________________
17
RS2
RS1
RS0
RANGE
NOMINAL RESISTOR VALUE
0
±2A
R_E = 1M
0
1
±2A
R_E = 1M
0
1
0
±20A
R_D = 100k
0
1
±200A
R_C = 10k
1
0
±2mA
R_B = 1k
1
0
1
±25mA
R_A = 80
1
0
External
—
1
±25mA
R_A = 80
Table 6. Current Range Selection
CLENABLE
MODE
1
Clamps enabled
0
Clamps disabled
Table 7. Clamp Enable
HI-ZMSR
HI-Z_
MSR_ STATE
1
Measure output enabled
0
1
High-Z
1
0
High-Z
0
High-Z
Table 8. MSR_ Output Truth Table
DISABLE
CONDITION
DUTH_
DUTL_
0
X
High-Z
1VMSR > VTHMAX and VTHMIN
01
1VTHMAX > VMSR > VTHMIN
11
1VTHMAX and VTHMIN > VMSR
10
1VTHMIN > VMSR > VTHMAX*0
0
Table 9. Comparator Truth Table
*
VTHMAX > VTHMIN constitutes normal operation. This condition, however, has VTHMIN > VTHMAX and does not cause any problems with
the operation of the comparators.