AMP =
rm
RSHUNT
=
0.168
0.08
= 2.1
Finally choosing R
a
=R
b
and R
c
=R
d
, the differential gain of the circuit is:
(10)
AMP =
Rc
Ra
= 2.1
An amplification gain of 2.1 was chosen. The same amplification is obtained for all the other devices, taking into
account the OCP current and the shunt resistance, as described in Table 1.
The RC filter for output amplification is designed to have a time constant that matches noise parameters in the
range of 1.5 μs:
(11)
4 ⋅ ι = 4 ⋅ R
e
⋅ C
c
= 1.5µs
(12)
C
c
=
1.5µs
4 ⋅ 1000
= 375pF 330pFselected
Table 4.
Amplifying networks
Phase
Amplifying network
RC filter
R
a
R
b
R
c
R
d
R
e
C
c
Phase U
R30
R32
R29
R33
R31
C25
Phase V
R35
R37
R34
R39
R36
C29
Phase W
R40
R42
R38
R43
R41
C31
UM2702
Current sensing amplifying network
UM2702
-
Rev 1
page 16/34