LB1947VC

No.A2035-9/11

Notes on Usage

1. VREF pin

Because the VREF pin serves for input of the set current reference voltage, precautions against noise must be taken.

2. GND pin

The ground circuit for this IC must be designed so as to allow for high-current switching. Blocks where high current

flows must use low-impedance patterns and must be removed from small-signal lines. Especially the ground

connection for the sensing resistor RE at pin E, and the ground connection for the Schottky barrier diodes should be in

close proximity to the IC ground.

The capacitors between VCC and ground, and VBB and ground should be placed close to the VCC and VBB pins,

respectively.

3. CR pin setting (Switching off time, Noise cancel time)

The noise cancel time (Tn) and the switching off time (Toff) are set by the following expressions:

Noise cancel time: Tn

≈ C × R × ln {(1.0 − RI) / (4.0 − RI) [sec]

CR charge current: 1.3mA

Switching off time: Toff

≈ −C × R × ln (1.0 / 4.8) [sec]

Internal configuration at CR pin

C:680pF

CR

VCC line

One-shot multi-blanking

time circuit

CR constant range: R = 4.7k to 100k

Ω

C = 330pF to 2200pF