M37517F8HP Datasheet, PDF (38/98 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7517 Group
Current Integrator
Current integrator integrates the current which flows through
sense resistor (10 mΩ) connected between ISENS0 pin and
ISENS1 pin. The current between sense resistor makes electrical
potential difference between ISENS0 pin and ISENS1 pin, and it is
integrated by the built-in integrator. The output of integrator is con-
nected to comparator, and the integrator and comparator
measures about 1 mA current.
Setting the current integrate enable bit “1”, the current integrator
starts the operation.
Current integrate mode
Setting the current integrate mode bit “0”, input of the level shift
circuit is connected to the ISENS1 pin and ISENS0 pin, and the
current integrator measures the electrical potential difference be-
tween ISENS1 pin and ISENS0 pin. Each electrical potential of the
ISENS1 pin and ISENS0 pin is added AVCC/2 by level shift circuit,
and then output of the level shift circuit is input to integrator. This
makes enable to minus level input to ISENS1 pin, and the current
integrator can measure both polarity current.
The output of the integrator is connected to the comparator. The
integrator integrates input voltage between ISENS1 pin and
ISENS0 pin. And when output of the integrator amounts to com-
pared voltage, output of the comparator rises “H”, and charge
(discharge) counter is increased 1 count. And at the same time,
electric charge of the integrator’s capacitor is discharged, then the
integrator starts next integration. Charge (Discharge) counter is
counting the number of the times “H” output of the comparator
during integration period (125 ms), and at the end of the period,
charge (discharge) counter is latched onto charge (discharge)
counter latch. Then charge (discharge) counter is cleared “0”, and
starts new count. At the end of the period, current integrate inter-
rupt occurs also.
The current integrator has 2 set of comparator and counter for dis-
charge and charge, and only discharge counter counts up in
discharge state, and only charge counter counts up in charge
state. The integrator and comparator are designed to sense ap-
proximate 1 mA current, then 1 count of counter means
approximate 1 mA Therefore reading the value of counter latch
means measuring the total current which flows the sense resistor
during integrate period (125 ms).
The calibration integrates the current of the period selected by the
calibration period selection bits, after discharging the electric
charge accumulated in the capacitor of the integrator.
10mΩ
ISENS0
ISENS1
XX0
001
011
101
XX0
001
011
101
Level shift
circuit
Current integrate control register
b2 b1 b0
XX0 : Current integrate mode
001 : Zero calibration
011 : Full calibration for discharge
101 : Full calibration for charge
0.1V
Fig. 44 Block diagram of Current integrator
Edge detect
AD conversion
complete signal
Calibration control signal
XCIN
Calibration
control circuit
125 ms Timer
Calibration control signal
Current integrate
interrupt
Charge counter
Charge counter latch
Discharge counter
Calibration control signal
Discharge
counter latch
10bit AD
AD conversion
complete signal
ANi
Data Bus
Rev.1.01 Aug 02, 2004 page 38 of 96