ISD91200 Series Technical Reference Manual
Release Date: Sep 16, 2019
- 390 -
Revision 2.4
7.2
Bridge Sense
7.2.1
Functional Description
The Bridge Sense block consists of three parts, a low noise bandgap, an LDO and an Instrumentation
Amplifier (IA). See Figure 3 for the block diagram.
The bandgap circuit generates a reference voltage, VBG. The LDO uses VBG to make a stable voltage
that can be used to bias a Wheatstone bridge. The maximum output current of the LDO is 10mA. The
IA can sense and amplify the output signal of the Wheatstone bridge and buffer it before it goes to a
high resolution Sigma Delta ADC (SDADC).
7.2.2
Features
Bandgap
•
Low noise
•
Trimmable
LDO
•
Output voltage from 1.5 to 4.5V with 0.3V steps.
•
Current limit
Instrumentation Amplifier
•
Gain adjustable from 1x to 128x
•
System chopper at the input
7.2.3
Block Diagram
VCCA
1uF
Low Noise
Bandgap
BS- LDO
BSLDO
BSP
BSN
To
SDADC
Main-
LDO(1.5V)
VMID(0.75V)
DSADC
VCCA
VCCD
Note :
VCCA >1.8V
Note :
VCCA >1.8V
Note :
VCCD >1.8V
Max: 4.5V
IA
VCCA
0.75V
1.5V
DSADC
Vref
BSP
BSN
Bridge Sensor
VCCA
Core cell
Figure 3. Block diagram of Bridge Sense.