LTC6091_15 Datasheet, PDF (11/22 Pages) Linear Technology – Dual 140V, Rail-to-Rail Output, Picoamp Input Current Op Amp

LTC6091
APPLICATIONS INFORMATION
General
The LTC6091 dual high voltage operational amplifier
is designed in a Linear Technology proprietary CMOS
process enabling a rail-to-rail output stage with a 140V
supply while maintaining precision, low offset, low offset
drift and low noise.
Power Supply
The LTC6091 consists of single monolithic die containing
two LTC6090 amplifiers assembled in a single exposed-
pad QFN package. Since both amplifiers share the same
substrate, V^– pins (Pin 3 and Pin 7 ) must be tied together
and to the exposed pad underneath. The V⁺A (Pin 14) and
V⁺B (Pin 10) may be supplied independently. The LTC6091
works off single or split supplies. Split supplies can be
balanced or unbalanced. For example, two ±70V supplies
can be used, or a 100V and –40V supply can be used.
The V+ and V– pins should be bypassed with high qual-
ity surface mount ceramic capacitors. See Board Layout
section for recommendations. When using split supplies,
supply sequencing does not cause problems.
Input Protection
As shown in the Block Diagram, the LTC6091 has a
comprehensive protection network to prevent damage to
the input devices. The current limiting resistors and back-
to-back diodes are to keep the inputs from being driven
apart. The voltage-current relationship is that of a resistor
in series with a diode until the voltage difference between
the pins reaches 12V. At that point the Zener diodes turn
on. Any additional current into the pins will snap back the
input differential voltage to 9V.
In the event of an ESD strike between an input and V^–,
the voltage clamps and ESD device fire providing a cur-
rent path to V^– protecting the input devices. The input
pin protection is designed to protect against momentary
ESD events. A repetitive large fast input swing (>5.5V and
<20ns rise time) will cause repeated stress on the MOSFET
input devices. When in such an application, anti-parallel
diodes (1N4148) should be connected between the inputs
to limit the swing.
Output Disable
Each amplifier of the LTC6091 has its own output disable
(OD) pin (Refer to Figure 1). The OD pin is an active low
disable with an internal 2M resistor that will pull up the
OD pin enabling the output stage. The OD pin voltage is
limited by an internal Zener diode tied between COM and
OD. When the OD pin for a particular channel is asserted
low with respect to its COM pin, the output stage for that
LOW
VOLTAGE
CONTROL
LOW
VOLTAGE
CONTROL
V⁺A
2M
ODA
10k
15
12 ^{TFLAGA 6k}
LTC6091
V⁺B
ODB
11
2M
20k V^–
8 ^{TFLAGB 6k}
10k _COMA
16
6k
500Ω
10k _COMB
4
6k
500Ω
V^–
6091 F01
Figure 1. Low Voltage Interface Example for Output Disable
For more information www.linear.com/LTC6091
6091fa
11