LB8658FN, LB8658PL

No.7983-13/16

Application Design Notes

(1) Constant-voltage setting for OUT1 to OUT8

“H” output voltage for OUT1 and OUT2 can be set by the VC1 pin input voltage.

The setting formula is as follows:

(OUT1/OUT2 output voltage) = (VC1 input voltage)

×5.23

Correspondingly, OUT3 and OUT4 can be set by VC2, OUT5 and OUT6 can be set by VC3, and OUT7

and OUT8 can be set by VC4. The setting formula is as follows:

(OUT3/OUT4 output voltage) = (VC2 input voltage)

×5.23

(OUT5/OUT6 output voltage) = (VC3 input voltage)

×5.23

(OUT7/OUT8 output voltage) = (VC4 input voltage)

×5.23

In addition, if the right side setting of the above formula exceeds the supply voltage (VB), the output

voltage is saturated.

(2) Output pin oscillation prevention capacitor for OUT1 to OUT8 constant-voltage control

For constant-voltage control of OUT1 to OUT8, a capacitor must be placed between OUT pins in order to

prevent oscillation.

Test capacitor values between 0.01

µF to 0.1µF and choose a value that does not cause output oscillation problems.

However, for the saturated drive, no oscillation prevention capacitor is necessary.

(3) Constant-current setting of OUT9 and OUT10

Constant-current setting between OUT9 and OUT10 depends on the IC pin input voltage and IMA/IMB pin

connection resistance (current detection resistor). The IMA pin is connected to the GND side of H-bridge and the

IMB pin is connected to the negative input of constant-current control amplifier. The IMA pin and the IMB pin are

short circuited on the PWB to be used. (Short circuit near the current detection resistor is recommended.)

As shown in the block diagram, the output current is controlled so that the IC pin input voltage can be equal to the

voltage generated on the current detection resistor, which is connected between IMA (IMB) and GND.

The formula for output current is as follows:

(Output current) = (IC input pin voltage)

÷ (current detection resistance)

In addition, since the constant-current control block is connected to PGND inside the IC, when the voltage is

supplied to the IC pin with partial resistance, GND side of the resistor must be connected to PGND.

(4) ICH pin

For the application when current is switched between shutter “Close” and “Open”, the ICH pin is used.

The ICH pin is changed to “L” only in “Open” mode (refer to the Truth table). This allows the current for shutter

“Open” to be set (switched) lower than the current for shutter “Close”.

The IC pin input voltage is switched by the combined resistance value which is obtained from resistance connected

to the IC pin (2 resistors between VREF and GND) and a resistor connected to the ICH pin.

(5) Fast charge/discharge circuit for the FC pin

In order to support high speed shutter control (sequential shutter), a built-in fast charge/fast discharge circuit is

implemented in the shutter control block (OUT9 and OUT10).