3
AN1270.0
September 27, 2006
Finally the center off position provides a means of
connecting a repetitive signal source to the PD input. This is
so the user can observe power-down enable/disable timing.
An important note to remember when using the PD - BNC:
1. Place the switch in center-off position.
2. The PD input is referenced to VCC/VEE. The low
amplitude of the PD input must match the VEE voltage.
The high amplitude must be close to VCC.
Comparator Threshold Rails
Each comparator has two thresholds. CVA/CVB. The data
sheet explains the operation of these analog inputs.
However, it should be mentioned that while the ISL55142
(Dual) and ISL55143 (QUAD) comparators have separate
threshold inputs for each comparator, the evaluation boards
have all CVA inputs tied to single CVA_BUS. Accordingly, all
CVB inputs are tied to a single CVB_BUS.
Initial Power-Up
Please refer to the device specification for power-up
sequencing and current requirements. Also note that the
frequency of operation and number of comparators will
determine the current needed. There are graphs in the
specification regarding current characteristics.
When first powering up the device, set all power bus inputs
to minimum current levels needed for quiescent operation.
Check the device out statically with DC inputs on the VINP
pins and observe that the QA/QB outputs toggle when the
VINP voltage crosses the CVA and CVB thresholds.
Once static observations check out, you can then increase
power current limits for VCC/VEE and VOH/VOL and apply
higher frequency inputs to the VINP pins.
Layout Information
All evaluation boards have complete silk-screen information
regarding test points, jumpers and component placements.
The silk-screen on the board you receive will provide
up-to-date layout information.
Schematic Information
Schematics are drawn with physical location in mind. Any
changes in electrical circuitry will be updated in this
document as needed.
Included in the following pages are three schematics.
ISL55141 single comparator device, ISL55142 dual
comparator and ISL55143 quad comparator device. The
Evaluation boards are laid out for the TSSOP packages for
the ISL55141 and ISL55142, while the ISL55143 is the QFN
package. Please refer to the device specification for part
numbers/options for these and other package ordering.
Bill of Material
A bill of material of the ISL55142 evaluation board is
included on page 6. It provides sources for special
components such as the BNC connectors and banana jacks.
All other parts are QPL standard passive components. Refer
to device specification (FN6230) when ordering
replacements for actual ISL55141, ISL55142 or ISL55143
devices.
FIGURE 7. ISL55142 AND ISL55143 COMPARATOR
THRESHOLD CVA/CVB INPUTS ARE TIED
TOGETHER TO EITHER THE CVA_BUS OR
CVB_BUS.
QA0
2
QB0
3
QA1
4
VINP2
20
VINP0
26
CVB0
27
VO
L
11
VO
H
12
VO
L
13
VEE
14
VC
C
34
QB1
5
CVA2
19
VCC
15
VEE
33
QA2
6
QB2
7
QA3
8
QB3
9
CV
A3
16
VI
NP3
17
CVB3
18
VO
H
10
CVA1
22
VINP1
23
CVA0
25
CVB1
24
CVB2
21
VC
C
32
VEE
31
PD
28
ISL55143_QFN
CVB_BUS
CVA_BUS
Application Note 1270
