lb11947 Sanyo Semiconductor Corporation, lb11947 Datasheet - Page 10

• Manufacturer Part Number: lb11947
• Description: Pwm Current Control Type Dc Motor Driver + Switching Regulator
• Manufacturer: Sanyo Semiconductor Corporation

(Switching OFF time and noise canceling time set method)
Connection of C and R between CRA pin (pin 14), CRB pin (pin 12) and GND allows setting of the switching OFF time
and noise canceling time.
The noise canceling time Tnc and switching OFF time Toff is set approximately by the following equation.
[Noise canceling time Tnc]
[Switching OFF time Toff]
(Peak coil current set method)
The peak current value (set current) flowing through the motor coil is set by the sense resistor to sense the current
connected between EA pin (pin 25), EB pin (pin 2) and GND and by the reference voltage applied to VREFA pin (pin
15) and VREFB pin (pin 13).
Tnc
Toff
Ipeak = Vref/(5 Rs)
I
C
R
Ipeak : Set current
Vref : VREF pin application voltage [V]
Rs
.
= . C • R • ln{(1–RI)/(4–RI)}[s]
.
= . – C • R • ln(1/4.8) [s]
: CR pin charge current
: CR pin external capacitor
: CR pin external resistor
: Current sense resistor
[A]
[F]
[Ω]
[A]
[Ω]
LB11947
No. 7318 -10/14