tb6641fg TOSHIBA Semiconductor CORPORATION, tb6641fg Datasheet - Page 13

• Manufacturer Part Number: tb6641fg
• Description: Full-bridge Dc Motor Driver Ic
• Manufacturer: TOSHIBA Semiconductor CORPORATION

9.
OSC
PWM Constant-Current Control
The TB6641FG uses a peak current detection technique to keep the output current constant by applying
constant voltage through the VREF pin. When running in Discharge mode, the TB6641FG powers the motor
to operate in Short Brake mode.
(1)
(2)
Internal CLK
VREF/10
Control
circuit
OSC
OSC
GND
PWM constant-current control programming
The peak current upon the constant-current operation is determined by applying voltage on the VREF
pin. The peak current value is calculated by the following equation:
The PWM current-constant frequency is also programmable by using the capacitor of the OSC pin. The
oscillation frequency is approximated by using the following equation:
For preventing the overvoltage on connecting a detection resistor, the RSGND pin is driven High (the
outputs are turned off (Hi-Z)) when the applied voltage is over 0.4 V (typ.). The subsequent control of
the RSGND is the same as the ISD circuit. The ALERT pin is also driven High. However, when the IN1
and IN2 pins are pulled Low, the ALERT pin is pulled Low and the TB6641FG resumes the normal
operation.
It is recommended to use a detection resistor of over 0.1  for the RSGND pin.
Constant-current chopping
The TB6641FG enters Discharge mode when V
After a lapse of four internal clocks generated by the OSC signal, the TB6641FG shifts to Charge
mode.
OUT1
I
fosc = 0.42/(Cosc [F] × 10
O
= VREF/R × 1/10 [A]
V
RSGND
RSGND
VREF/10
R
V
RSGND
I
M
O
I
O
OUT2
VM
3
) = [Hz] (typ.)
Coil current
Discharge
Coil current
Control
0.4 V (typ.)
circuit
ISD
13
RSGND
Control
Charge
circuit
reaches the predetermined voltage (VREF/10).
1/10
Discharge
VREF
Analog input voltage
TB6641FG
2011-06-21