ISL55100B_14 Datasheet, PDF (8/14 Pages) Intersil Corporation – Quad 18V Pin Electronics Driver/Window Comparator

ISL55100B
Application Information
The ISL55100B provides Quad pin drivers and Quad dual level
comparator receivers in a small footprint. The four channels
may be used as bidirectional or split channels. Drivers have per
channel level, data and high impedance controls, while
comparators have per channel high and low threshold levels.
Receiver Features
The receivers are four independent window comparators that
feature high output current capability and user defined high and
low output levels to interface with a wide variety of logic
families. Each receiver comprises two comparators and each
comparator has an independent threshold level input, making it
easy to implement window comparator functions. The CVA and
CVB pins set the threshold levels of the A and B comparators
respectively. COMP HIGH and COMP LOW set all the comparator
output levels and COMP HIGH must be more positive than COMP
LOW. These two inputs are unbuffered supply pins, so the
sources driving these pins must provide adequate current for the
expected load. COMP HIGH and COMP LOW typically connect to
the power supplies of the logic device driven by the comparator
outputs. The ‘truth table” for the receivers is given on page 3.
Receiver outputs cannot be placed in a HIZ state and do not
incorporate any on-chip short circuit current protection.
Momentary short circuits to GND or any supply voltage, won’t
cause permanent damage, but care must be taken to avoid
longer duration short circuits. If tolerable to the application,
current limiting resistors can be inserted in series with the QA(0-3)
and QB(0-3) outputs to protect the receiver outputs from damage
due to overcurrent conditions.
Driver Features
The drivers are single-ended outputs featuring a wide voltage
range, an output stage capable of delivering 125mA while
providing a low out resistance and HIZ capability. The driver
output can be toggled to drive one of two user defined output
levels High (VH) or Low (VL).
Driver waveforms are greatly affected by load characteristics. The
ISL55100B actually double bonds the VH(0-3) and VL(0-3) supply
pins for each channel. The Driver Output Pins (DOUT(0-3)) are
triple bonded. Multiple bond wires help reduce the effects of
Inductance between the IC Die (Wafer) and the packaging. Also
the QFN style of packaging reduces inductance over other types
of packaging.
While the inductance of a bond wire might seem insignificant, it
can reduce high-frequency waveform fidelity. So this should be
borne in mind when doing PCB layout and DUT interconnect. Lead
lengths should be kept as short as possible, maintaining as much
decoupling on the drive rails as possible and make sure scope
measurements are made properly. Often the inductance of a
scope probe ground can be the actual cause of the waveform
distortion.
VH and VL (Driver Output Rails)
Sets of VH and VL pins are designated for each Driver. These
are unbuffered analog inputs that determine the Drive High
(VH) and Drive Low (VL) Voltages that the drivers will deliver.
These inputs are double bonded to reduce inductance and
decrease AC Impedance.
Each VH and VL should be decoupled with 4.7µF and 0.1µF
capacitors to ground. If all four Driver VH/VLs are bussed, then
one 4.7µF can be used. Layouts should also accommodate the
placement of capacitance “across” VH and VL. So in addition to
decoupling the VH/VL pins to ground, they are also decoupled
to each other.
Logic Inputs
The ISL55100B uses differential mode digital inputs and can
therefore mate directly with LVDS or CML outputs. Single- ended
logic families are handled by connecting one of the digital input
pins to an appropriate threshold voltage (e.g., 1.4V for TTL
compatibility).
LOWSWING Circuit Option
The drivers include switchable circuitry that is optimized for
either low (VH-VL < 3V) or high output swings. Configuring the
part is accomplished via the LOWSWING pin. Connecting
LOWSWING to V_EE selects the circuits optimized for low
overshoots at low swing operation. Connecting the pin to VCC
enables the large signal circuitry (see Figure 7).
With LOWSWING = V_EE, the low swing circuitry activates
whenever VH < V_EE + 5V. Set LOWSWING = V_EE only if the
output swing (VH-VL) is less than 3V and better than 10%
overshoots are required.
For the best small (low swing) signal performance, the VH/VL
common mode voltage [(VH + VL)/2] must be V_EE + 1.5V. So if
V_EE = 0V and the desired swing is 500mV, set VH = 1.75V and
VL = 1.25V.
Driver and Receiver Overload Protection
The ISL55100B is designed to provide minimum and balanced
Driver R_OUT. Great care should be taken when making use of
the ISL55100B low R_OUT drivers as there is no internal
protection. There is no short circuit protection built into either
the driver or the receiver/comparator outputs. Also there are
no junction temperature monitors or thermal shutdown
features.
The driver or receiver outputs may be damaged by more than a
momentary short circuit directly to any low impedance voltage.
Driver protection can be obtained with a 50Ω series
termination resistor that is properly rated.
External Logic Supply Option (V_EXT)
Connection of the V_EXT Pin to a 5.5V DC Source (referenced to
V_EE) will reduce the V_CC-V_EE current drain. Current drain is
directly proportional to Data Rate. This option will help with
Power Supply/Dissipation should heat distribution become an
issue.
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FN6229.2
December 4, 2014