M61040FP Datasheet, PDF (13/25 Pages) Mitsubishi Electric Semiconductor – Smart battery protection and monitoring IC

Smart battery protection and monitoring IC
M61040FP
(2) Charge / discharge current detection circuit
The Charge/Discharge current detection circuit is shown in figure 6. This circuit is composed of
offset voltage adjustment circuit, buffer amplifier and resistor network.
The pre-amplifier amplifies the voltage of sense resistance to the voltage based on GND. The
voltage gain can be selected by microcomputer commands.
Buffer amplifier does an impedance translation between input and output.
Vreg = 5.2V
To Multiplexer
circuit
AMP3 R
+
−
R
AMP2
+
−
RC1
Charge current
Monitor
RC3
RC2
From Serial to Parallel
conversion circuit
R
R
−
+
AMP4
Offset voltage
Adjustment circuit
RD1 _−
+
Discharge current
Monitor
RD2
AMP1
From Serial to Parallel
conversion circuit
VIN 11
RD3
VIN 10
Rsence
GND
Figure 6. Charge / discharge current detection circuit
The offset voltage can be compensated by adjustment circuit.
The function in detecting discharge current is shown in figure 7. The differential voltage of sense
resistor is input to +(plus) terminal of AMP 1 when discharge current is flowing in sense resistor.
Selecting high voltage gain by microcomputer’s command is capable of monitoring very little
discharge current accurately.
The differential voltage of sense resistor is input to -(minus) terminal of AMP 2 when charge current
is flowing in sense resistor. The methods of detecting in charging are the same as in discharging
except that AMP2 reverses input voltage before outputting.
NOTE: Regard 500µs as the standard of settling time by voltage change in this block.
Vb = Idis × Rsens × Gain
+
AMP2
−
RC1
RC2
RC3
From I/F circuit
RD1 _−
AMP1
+
RD2
Va = Idis × Rsens × Gain
RD3
VIN 10
VIN 11
Rsence
Charge current Icha Discharge current Idis
Figure 7.Charge/Discharge current detection
Mitsubishi Electric
(13/25)