Datasheet

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November 30, 2010
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8.4 Mode 12. Ib1: resistive bridge, ref. is I
bridge
,+/- 0.25% imbalance
This mode is similar to mode 11. The connection of the bridge and the resistor is shown in Figure 14 .
The difference with mode 11 is that the bridge imbalance range is +/- 0.25%. The voltage
across the reference resistor should be between 0.1 V and 0.2 V, as in mode 11.
Phase Measured voltages Output periods
1 V
offset
Toffset=N*K
2
*Voffset
2 V
ab
+V
offset
Tab= N*K
2
*(Vab+Voffset)
3 15*Vcd+V
offset
Tcd=N*K
2
*(15*Vcd+Voffset)
Table 22. Measured voltages of Ib1 mode
The bridge output voltage is amplified 15 times before it is processed in the same way as the reference
voltage. The voltages measured during each phase are indicated in Table 22 . The specifications of the Ib1
mode are listed in Table 23
To find the bridge imbalance, the microcontroller calculates
ref
CD
phasephase
phasephase
IR
V
TT
TT
M =
−
−
=
12
13
15
1
(5)






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Parameter (V
DD
= 5 V) Typical value
K
2
56 s/V
V
0
0.54 V
Bridge excitation AC Vdd
excitation current (max E - F) 20 mA
Bridge resistance 250-10k
Bridge output Voltage <+/- 0,2V
Accuracy 12 bits (over =/- 0.2V)
Offset
<10 V
Resolution (SF=0)
< 7 V
Table 21. Specifications of the Ib2 mode
Parameter (V
DD
= 5 V) Typical value
K
2
56 s/V
V
0
0.54 V
Bridge excitation AC Vdd
excitation current (max E - F) 20 mA
Bridge resistance 250-10k
Bridge output Voltage <+/- 12,5 mV
Accuracy 10 bits (over +/- 12,5mV)
Offset
<10 V
Resolution (SF=0) 700 nV
Table 23. Specifications of the Ib1 mode