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© 2007 Semtech Corp. / Rev. 6, 2/20/07 www.semtech.com
TEST AND MEASUREMENT PRODUCTS
E737
Circuit Description (continued)
HIZ
HIZ is a digital input which places the FORCE output
into a high impedance state, regardless of the operat-
ing mode (forcing current or voltage.) This function al-
lows the PMU to be connected directly to the pin elec-
tronics without an isolation relay while NOT adding any
leakage current.
DISABLE
DISABLE is a digital input which places DUT LTH, DUT
GTL, I/V MONITOR, and PASS/FAIL* into high imped-
ance states.
Force Voltage / Measure Current Mode
In the FV / MI mode, VINP is a high input impedance,
analog voltage input that maps directly to the voltage
forced at the DUT (see Figure 1), where FORCE =
VINP.
A current monitor is connected in series with the Op
Amp driving the FORCE voltage. This monitor gener-
ates a voltage that is proportional to the current pass-
ing through it, and its output is brought out to I/V MONI-
TOR. The monitor’s voltage may also be evaluated
using the Window Comparator whose operation is in
accordance with the FV/MI functional truth table (Table
6).
I/V MAX and I/V MIN are high impedance analog in-
puts that establish the upper and lower thresholds for
the window comparator (see Table 4). In the FV / MI
mode, a maximum voltage input corresponds to at least
a maximum current output. Positive current is dened
as current owing out of the PMU.
I/V MAX
I/V MIN Comparator Threshold
+8.0V > Imax (full scale)
0V 0
-8.0V < Imin (full scale)
Table 4.
The voltage at I/V MONITOR follows the equation:
I(measured) = I/V MONITOR / (4.0 * REXT).
Nominally, the external resistors (RA, RB, RC, and RD)
should be chosen such that Imax * REXT = 2.0V.
Force Current / Measure Voltage Mode
In the FI / MV mode, IVIN is a high input impedance,
analog voltage input that is converted into a current
(see Table 5) using the following relationship:
FORCE = IVIN / (4.0 * REXT)
where positive current is dened as current owing out
of the PMU.
IVIN Forced Current
+8.0V Imax (full scale)
0V 0
-8.0V Imin (full scale)
Table 5.
The resulting DUT voltage is then tested via the SENSE
input by a window comparator, whose functional truth
table is shown in Table 7.
I/V MAX and I/V MIN are high impedance analog in-
puts that establish the upper and lower thresholds for
the window comparator. In the FI / MV mode, the refer-
ence inputs translate 1:1 to SENSE level thresholds.