Overview

The LB8118M is an actuator driver IC designed for portable CD players that operate at 2.4 V (two Ni-Cd batteries) or 3.0 V (two dry cells). Because the four-channel driver control outputs are divided into two groups, this device reduces power dissipation considerably during double-speed play.

Functions and Features

? H bridge drivers (output dynamic range maximum is about 2 V) on chip for four channels to drive each CD actuator (the focus coil, the tracking coil, the spindle motor, and the sled motor).

? Step-up circuit (voltage to be set by an external resistor) on chip that is used to apply voltage to the CD DSP, ASP and microcontroller. Center-tap coil for step-up circuit makes it possible to supply the driver control voltage. (However, the drive Tr, L, C, and Di are all external.)

? Oscillator circuits for each converter on chip. (C is external.)

? Four-channel driver control output is divided into two groups (the focus/tracking group and the spindle/sled group) for minimum loss at double-speed playback. Highest operating voltage detected in each group is supplied for each 2ch H bridge driver after PMW conversion. The single channel PWM drive without dividing the outputs into two groups is also possible. (However, the PWM PNP-Tr, NPN-Tr, L, C, and Di are all external.)

? The dynamic range of 4-channel H bridge driver output voltage is up to 2 V on the focus and tracking side, and can be set by the Vosat pin on the spindle and sled side. However, if the 4-channel H bridge voltages in the H bridge driver block are the same, the maximum voltage is determined using the Voset pin.

? Sled motor driving mode is switchable between step drive mode for lower power dissipation, and normal V-type drive mode. (The other three channels are fixed to V-type.)

? In the spindle motor drive circuit, the control gain can be set higher for double-speed playback.

? PWM step-down circuit for external power operates when external power (4 V or higher) is supplied.

In this function, external power is converted to VCC power supply, and two type voltage setting is possible.

In playback mode, step-up voltage for DSP has to be set equal to or lower than VCC, but in charging the battery, it has to be set higher enough than VCC.

So step-down voltage (VCC) setting of two types is possible with two pairs of external resistor. (Switching port is provided.) (However, the PWM PNP-Tr, NPN-Tr, L, C, and Di are all external.)

? APC step-up power supply for the laser diode. (Also supports a pre-power supply for the internal bias.) The laser diode is controlled with a voltage of roughly 0.5 V.

? Battery pulse charging function on chip. (However, the drive NPN-Tr, and the current feedback C and R are external.)

? Battery check comparator on chip.

? The system can be started up and stopped by outputs from the microcontroller.

? Actuator muting function on chip (for all four channels simultaneously).

? Thermal shutdown circuit on chip