BH6504K ROHM Co. Ltd., BH6504K Datasheet - Page 11

• Manufacturer Part Number: BH6504K
• Description: Pwm Driver For Cd And Md Players
• Manufacturer: ROHM Co. Ltd.

FCircuit operation
(1)
This is an H bridge driver with four N-type FETs in the out-
put stage. Output polarity and PWM duty vary in propor-
tion to the input differential voltage between V
the absolute value. The load is direct-PWM-driven by the
square wave with this varying duty. This is a voltage feed-
back driver and so delivers a constant gain regardless of
battery voltage variation.
(2)
The DC / DC converter that generates the voltage need-
ed to drive the FETs of the output-stage H bridge. Pre.V
is raised to 6.5V by attaching an inductance, Schottky
barrier diode, and capacitor.
(3)
(1) Free-running oscillation
The free-running oscillation frequency of the triangular
waves can be set with an attached resistor (Rt, between
pin 16 and the ground) and capacitor (Ct, between pin 15
and the ground). The triangular wave has an amplitude
of 3 / 5
at the bottom. The ratio between rise time and fall time
is 3: 1. Free-running frequency (ft) is determined with the
following equation:
236
Operational amplifier
Optical disc ICs
ft=
PWM driver
DC / DC convertor
Triangular wave generator
4
3
Pre.V
S
CC
Ct
at the top and V
S
Rt 1
*
1
3
5
F
Pre.V
V
(approximately 0.7V)
F
cc
C
, and to
CC
BH6504K