BD7902 데이터 시트보기 (PDF) - Unspecified

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BD7902

6CH Power Driver for CD-ROM, DVD-ROM

Unspecified 

Optical disc ICs

BD7902CFS

4. Torque command (spindle: pin 24, sled motor: pin 28 and 29) / output current detection terminals (spindle: pin 20, sled

motor: pin 31 and 32)

The relation between the torque command input and the output current detection terminals input is expressed as

shown below:

SPRNF

SLRNF

FWD rotation

Dead zone +

Dead zone −

SPIN

VC

SLIN1, 2

The input-output gain (gm) and the output-limit current (ILIM) depend on the resistance of RNF (output current

detection resistor). Please refer to the following expression.

The gain to drive the spindle or the sled motor can be decreased by connecting a resistor in series to each input

terminal.

Gain expression

Spindle

Input-output gain gm (A/V)

1.0/RNF

Output-limit current Ilim (A)

0.47/RNF

Gain with the added resistor gm (A/V) 15k/{SPRNF×(Rin+15k)}

Sled

0.5/RNF

0.47/RNF

0.5×47k/{SLRNF×(Rin+47k)}

Rin : added series resistor

5. PWM oscillation frequency

The PWM oscillation for driving the spindle and sled is free running. The oscillating frequency is 100kHz (typ.).

6. Muting functions

a) VC-drop muting

When the voltage at VC terminal (pin 27) drops to a value lower than 0.7V (typ.), the outputs of all the channels are

turned off. Set the VC terminal voltage to larger than 1.0V.

b) VCC-drop muting

When the voltages at DVCC terminal (pin 54) and VCC terminal (pin 51) drop to lower than 3.8V (typ.), the outputs of

all the channels are turned off.

c) Over voltage protection circuit

When the voltages at VCC terminal (pin 51) drop to uper than 15.5V (typ.), the output of only the spindle block is

turned off.

7. Thermal-shutdown

A thermal-shutdown circuit (over-temperature protection circuit) is built in to prevent the IC from thermal breakdown.

Use the IC under the thermal loss allowed to the package. In case the IC is left running over the allowable loss, the

junction temperature rises, and the thermal-shutdown circuit works at the junction temperature of 175°C (typ.) (the

outputs of all the channels are turned off). When the junction temperature drops to 150°C (typ.), the IC start operating

again.

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