SAMHOP Microelectronics Corp.
SM16706P/SP/F/FN
16-BIT CONSTANT CURRENT LED DRIVER
[1] Output Current (IOUT)
I
OUT is set by the enternal resistor (R-EXT) as shown in Figure1.
[2] Total supply voltage (VLED)
This device can operate at 0.4~0.7V (VOUT). When a higher voltage is input to the device, the excess
voltage is consumed inside the device, that leads to more power dissipation.
In order to minimize power dissipation and loss, we would like to recommend to set the total supply voltage
as shown below,
V
LED (total supply voltage)=VOUT (IC Supply Voltage)+ Vf (LED Forward voltage)
+ VDS (MOSFET Voltage Drop)
When the total supply is too high considering the power dissipation of this device, an additional R can
decrease the OUT voltage (VOUT).
PATTERN LAYOUT
V
LED = 3 ~ 4 (V)
VDD
SDM4952
SDM4953
SDM9435A
VDS
SCAN
VDD
Vf
V
DD
ENABLE
CLOCK
LATCH
OUT0
VOUT
OUT15
SERIAL-IN
R-EXT
GND SERIAL-OUT
CPU
VDD
V
DD
Vf
ENABLE
CLOCK
LATCH
OUT0
VOUT
OUT15
SERIAL-IN
R-EXT
GND SERIAL-OUT
[3] Pattern Layout
This device has only one ground pin that means signal ground pin and power ground pin are common.
If ground pattern layout contains large inductance and impedance, and the voltage between ground
and LATCH, CLOCK terminals exceeds 2.5V by switching noise during operation, this device may miss-
operate. So we would advise you to pay attention to pattern layout to minimize ground inductance.
Page 11
V.2.0 MAY,2003
SAMHOP [ SAMHOP MICROELECTRONICS CORP. ]
