BH6505K [ROHM]
PWM driver for CD and MD players; PWM驱动程序CD和MD播放器
| 型号： | BH6505K |
| 厂家： | 
ROHM |
| 描述： | PWM driver for CD and MD players |
| 文件： | 总12页 (文件大小：210K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Optical disc ICs
PWM driver for CD and MD players
BH6505K
The BH6505K is a 4-channel PWM driver designed for CD and MD player motor and actuator drives. The power MOS-
FET output stage allows for applications with low power consumption. This IC also has a charge pump circuit and stan-
dard operational amplifier (needed for power MOSFET gate drives), and so supports a wide spectrum of applications.
FApplications
Portable CD players, MD players
FFeatures
1) Low power consumption.
5) Allowsforfree-runningandclocksynchronizationop-
eration.
2) A minimum of attached components.
3) Goodgainprecisionbecauseofthevoltagefeedback
circuit.
6) Internal standard operational amplifier.
7) Internal charge pump circuit for gate drive.
4) Internal mute function for channels 1 and 2.
FAbsolute maximum ratings (Ta = 25_C)
FRecommended operating conditions
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Optical disc ICs
BH6505K
FBlock diagram
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Optical disc ICs
BH6505K
FPin descriptions
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Optical disc ICs
BH6505K
FInput / output circuits
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BH6505K
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Optical disc ICs
BH6505K
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BH6505K
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Optical disc ICs
BH6505K
FElectrical characteristics (unless otherwise noted, Ta = 25_C, BATTERY = 2.4V, Pre.VCC = 3.0V, VC = 1.5V,
fCLK = 176.4kHz, RL = 8Ω–47µH)
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Optical disc ICs
BH6505K
FMeasurement circuit
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Optical disc ICs
BH6505K
FCircuit operation
(1) PWM driver
(2) Clock synchronization
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 VC, and to
the absolute value. The load is direct-PWM-driven by the
square wave with this varying duty.
The triangular wave can be synchronized by inputting to
the CLK pin (17 pin) a pulse wave equal to 0–Pre.VCC
(Vp-p). The following precautions should be kept in mind:
S The amplitude of the triangular wave decreases as the
clock frequency rises.
This is a voltage feedback driver and so delivers a
constant gain regardless of battery voltage variation.
(2) DC/DC converter
S The PWM driver is a voltage feedback driver, which
should preclude any problems unless the setting is such
that the triangular wave has an extremely small ampli-
tude.
The DC/DC converter that generates the voltage need-
ed to drive the FETs of the output-stage H bridge. Pre.VCC
is raised to 6.5V by attaching an inductance, Schottky
barrier diode, and capacitor.
S As mentioned above, a capacitor and resistor are also
required during clock synchronization.
(3) Triangular wave generator
(1) Freerunning
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 Pre.VCC at the top and VF (approximately 0.7V)
at the bottom. The ratio between rise time and fall time
is 3 : 1. Free-running frequency (ft) is determined with the
following equation:
3
4
1
ft=
S
VF
Ct S Rt 1*
3
5
Pre.VCC
FOperation notes
Attach a bypass capacitor (roughly 1µF) to the power
supply, at the base of the IC.
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Optical disc ICs
BH6505K
FApplication example
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Optical disc ICs
BH6505K
FElectrical characteristic curves
FExternal dimensions (Units: mm)
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