THAT1206 Datasheet, PDF (6/10 Pages) List of Unclassifed Manufacturers – InGenius High-CMRR Balanced Input Line Receiver

Page 6
InGenius Balanced Line Receiver
Preliminary Information
THAT1206
or THAT1246 Vcc
Ref
Gnd
CM out or N/C
+
Cb
In-
In-
In+
In+
Vee
Vcc
Vout
CM in or Sense
Connect
for
THAT1246
Vee
Figure 5. Dual PCB layout for THAT 1206 and THAT 1246
DIP version
Dual Layout Option
The THAT 1246 is a conventional balanced
line-receiver that is pin-for-pin compatible with the
Analog Devices SSM2143 and Burr-Brown INA137.
Though the THAT 1200 series is not pin-compatible
with the THAT 1246, the PCB layouts shown in Fig-
ures 5 and 6 provide manufacturers with the option
to stuff a PCB with any of these input stages. Note
that these figures are not to scale. The interconnects
should be as short as practicable constrained only by
component size and relevant manufacturing consid-
erations.
When a THAT 1200 series IC is installed, capaci-
tor Cb is connected between CM In and CM Out.
When the THAT 1246 (or SSM2143 or INA137) is
used, capacitor Cb is removed, and a jumper con-
nects the Vout and Sense pins.
Input Protection
Figure 7 shows the internal overvoltage protection
circuitry at the IN+, IN-, and CM IN pins. The values
of R and R’ vary with actual part number as shown in
Table 3.
While the internal protection circuitry shown is
adequate to keep the combination of signal and com-
mon mode voltages from driving the internal inputs
beyond the power supply rails, the circuitry does not
provide adequate protection against most ESD inci-
dents. Since these ICs will very often connect directly
to the outside world, it is mandatory that additional,
external protection from ESD be provided. Any un-
protected InGenius input will fail when subjected to
ESD if this protection circuitry is omitted. Addi-
THAT1206 Vcc
Gnd
THAT1246
Ref N/C
In-
In- ^Vcc
In+
In+ Vout
Vee
Vee _Sense
CM Out
+
Cb
Vcc
Vout
CM in
Connect
for
THAT1246
Vee
Figure 6. Dual PCB layout for THAT 1206 and THAT 1246
Surface mount versions
tionally, proper ESD handling precautions must be
observed until the IC is properly affixed to the PCB.
Vcc
R
IN+
Vee
Vcc
R
IN-
R'
CM IN
R'
Vee
Figure 7. Internal input protection circuitry (see text)
Part No.
R
R’
THAT 1200
500W
23.5kW
THAT 1203
7kW
17kW
THAT 1206
7kW
17kW
Table 3. Input resistance values
Diodes D1-D6 in figures 3 and 4 show our recom-
mended approach to protecting the 1200 series from
ESD damage. This arrangement of 1N4148s and
12V Zener diodes permits the maximum allowable
input signal to reach the IC's input pins, but directs
high-energy ESD impulses to the rails. So long as the
supply rails are adequately decoupled, most ESD
events will be diminished to harmless levels.
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com