Switch capacitive instrumentation amplifier
Description
Applications
This is a general-purpose switched capacitive instrumentation
 Wheatstone-bridge (strain-gauges, hall-sensors etc.)
amplifier (SCInstAmp) intended for high accuracy measure-
 Inline current sensing (input voltages beyond supply rails)
ment applications. The instrumentation amplifier consists of
 Low voltage differential sensing of any kind
two gain stages:
 A fully differential input stage
 A differential to single ended output stage.
Both stages are digitally programmable giving a variety of gain
settings in the range 12.5 to 800 nominal. The input stage
supports fully rail-to-rail common-mode voltage. The input can
even go marginally beyond both VddA and VssA in e.g. inline
current sensing systems.
The amplifier operates in a 2-phase manner with amplification
(low to medium impedance level)
Technology
X-FAB: XC035–CMOS, Polysilicon 2 Module
Size: ~0.65 mm2.
Portable to other 180 nm CMOS with Schottky diodes.
Proven in silicon
Schematic
hence intrinsic offset and error cancellation periods; it can
even be used as time continuously amplifier if a filter capacitor
is applied on the output. When absolutely maximum accuracy
is required, it is recommended to sample the output voltage in
the amplification period and do appropriate average of those
values.
Features
 Low offset voltage (<10 µV)
 Fully rail-to-rail input level (even beyond)
 Programmable gain
(12.5 to 800 nominal, 25 to 1600 crossover)
 Handle bi-polar input voltages (Vout is symmetrical
around the common-mode base Vcm)
 High linearity
 Low supply current
 On-chip bias generators and multi-clock phase generator.
Requires only master clock signal and output common-
For further information please contact us
mode voltage base Vcm.
asic@delta.dk
1179.2.11
DELTA · Venlighedsvej 4 · 2970 Hørsholm · Denmark - Tel. (+45) 72 19 40 40 · asic@delta.dk · asic.madebydelta.com
Pin list
Signal name
VddA
Vcm
Vout
Ena
Ctrl4
Ctrl5
Ctrl6
Ctrl7
Vinneg
Vinnegcm
Vinposcm
Vinpos
Ctrl3
Ctrl2
Ctrl1
Ctrl0
CLKin
Vback
VssA
Direction
Description
Analog
Analog
Analog
Input
Positive power supply
Common-mode voltage VddA/2 or Vref
Output voltage (Vout-Vcm)
Enable amplifier
Input
Gain setting of differential input stage
Analog
Analog
Analog
Analog
Negative input voltage
Negative common-mode voltage
Positive common-mode voltage
Positive input voltage
Input
Gain setting of single ended output stage
Input
Analog
Analog
Input clock for switch cap switches
Capacitor back plate voltage (Vcm or VssA)
Negative power supply
Electrical characteristics
Parameter
Condition/Note
Power supply range
Supply current
Input offset
Input voltage, high
Input voltage, low
Vcm, out
Vout, high
Vout, low
CLK, frequency
Input, frequency
Vin, capacitance
Gain=800 filtered output
Beyond supply rail ESD diodes
will come into action
VddA/2 or Vref is recommended
Switched not static!
Minimum
Typical
2.7
VddA
50
300
<10
VddA+10 mV
VssA-10 mV
1.25
VddA-200 mV
VssA+200 mV
10
~DC
Maximum
Unit
3.6
V
µA
µV
VssA
V
<100
Fclk/20
100
kHz
pF
The average output voltage is as follows:
Vout  Vcm  Gain  Vinpos  Vinneg   Vinposcm  Vinnegcm 
1179.2.11
DELTA · Venlighedsvej 4 · 2970 Hørsholm · Denmark - Tel. (+45) 72 19 40 40 · asic@delta.dk · asic.madebydelta.com
Typical applications
1179.2.11
DELTA · Venlighedsvej 4 · 2970 Hørsholm · Denmark - Tel. (+45) 72 19 40 40 · asic@delta.dk · asic.madebydelta.com
1179.2.11
DELTA · Venlighedsvej 4 · 2970 Hørsholm · Denmark - Tel. (+45) 72 19 40 40 · asic@delta.dk · asic.madebydelta.com