e7804 Semtech Corporation, e7804 Datasheet - Page 8

• Manufacturer Part Number: e7804
• Description: 133 Mhz Quad Pin Electronics Driver And Window Comparator
• Manufacturer: Semtech Corporation

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when disconnected from VIO through ~50KW. To prevent
the comparator outputs from switching due to noise when
not in use, the CVA/B inputs should be parked >250mV
from ground. An external pin, OPN[0:3] one input for each
channel, is combined with the register bit, and will override
the internal register bit and open the S2 switch for the
channel. In its low state, the OPN input will not override and
force the switch closed. (It should be noted that OPN=
will also open S to disconnect the channel’s driver output
from the VIO pin.) OPN is a fast way of disconnecting the
lower voltage driver and comparator circuitry from the VIO
pin. When the comparator (and driver) are disconnected,
the voltage at the VIO pin may be in the range of the VEE
to VXX power supplies.
Parametric Measurements
The E7804 incorporates a switch matrix which permits
an External Parametric Measurement Unit (EPMU) to be
connected to one or more channel’s POUT pin. The EPMU
range is a function of the VEE and VXX power supplies
with ±40 mA capability. Typically, POUT is connected
directly to the VIO pin or connected by an inductor so as
to minimize the effect of the capacitance at the POUT pin
on the driver’s waveform and maximum frequency.
The EPMUF and EPMUS inputs are force and sense
inputs respectively and connect to the POUT output
pin through an internal, normally open, dual switch (S4).
There is one dual switch for each channel [0:3]. This
switch can be closed by serially programming the internal
register bit for the appropriate channel (see Table 2,
CH[0:3]_switches_&_states registers) denoted as S4 to a
logical “”. Logical “0” will open the switch. The switch and
metal lines for the EMPUF path are sized to accommodate
the higher currents (up to 40mA). Do not use EPMUS for
higher currents. The EPMUS line is the Kelvin sense path
for the external PMU.
Continuity Test Circuit
Each channel has a programmable Continuity Test Circuit
(CTC) which can be switched to its POUT pin. The CTC
sinks current in the range –5 to –250 µA as determined
by the voltage of the CTCFIV input pin which is common
to all CTC’s.
TEST AND MEASUREMENT PRODUCTS
Circuit Description (continued)
2007 Semtech Corp. / Rev. 7, 02/26/07
8
The relationship between the CTCFIV input voltage and the
resulting current produced by the CTC uses the resistor
REREF, as a reference. This gives a good degree of voltage
to current accuracy. The relationship is:
CTCLV input determines the voltage limit to which CTC
may sink current. CTCLV has a range of 0 to –2.0V and
is common to all channels’ CTCs. With POUT, connected
externally to VIO, then with CTC connected and sinking
current, the resultant voltage at VIO can be tested by the
channel’s comparators. As this voltage could be as low as
–2V, when performing a continuity test, a channel’s driver
should be disconnected in order to protect the driver, which
has a range of –0.2V to +5.2V. The driver output should
be disconnected by opening switch S when connecting
the CTC to the POUT pin. The CTC connects to the POUT
pin through the normally open switch S5. Switch S5 can
be closed by serially programming a logical “” via the
internal register for the appropriate channel. See Table
2,”CH[0:3]_switches_&_states write instruction for the
individual channels.
Note that the CTC’s use the external resistor on
the EREF pin to calculate the ICTC test currents.
The driver output impedance calibration also uses
this reference. If any CTC is switched in-circuit
(S5 closed), then attempting to calibrate the driver
output impedance will fail and not occur. No change
to the calibration values will take place.
A typical continuity test will program the CTC’s force current
to –00 µA, its voltage limit at –2V, and CVA and CVB at
–0.5V and –.5V, respectively, so as to detect shorts, opens
and continuity. typically, in this test, the DUT power supplies
are all set to zero volts. The continuity test will determine
if each pin of the DUT is connected to the pin channel in
the tester without shorts to supplies or ground.
The tested pins will test good if the resulting voltage from a
–00µA load on them results in ~–0.7V. This is the voltage
CTCLV = -2V
CVB = -1.5V
CVA = -0.5V
ICTC = –.09 * [CTCFIV(V) / REREF(W)].
0V
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E7804