MBI5170
8-Bit Constant Current LED Sink Driver with Gain Control
August 2004, VA.00
- 2 -
GND
9
10
11
12
13
14
15
16
SDO
R-EXT
VDD
1
2
3
4
5
6
7
8
CLK
LE/MOD/CA
SDI
0
OUT
OUT1
OUT2
OUT3
OUT6
OUT7
OUT4
OUT5
/SW
OE
Product Description
MBI5170 succeeds MBI5168 and also exploits PrecisionDrive
™ technology to enhance its output characteristics.
Furthermore, MBI5170 uses the idea of Share-I-O
™ technique to make MBI5170 backward compatible with
MBI5168 in both package and electrical characteristics and extend its functionality for run-time LED current gain
control in LED display systems.
MBI5170 contains an 8-bit Shift Register and an 8-bit Output Latch, which convert serial input data into parallel
output format. At MBI5170 output stages, eight regulated current ports are designed to provide uniform and
constant current sinks with small skew between ports for driving LED
’s with a wide range of forward voltage (Vf)
variations. Users may adjust the output current from 5 mA to 120 mA with an external resistor Rext, which gives
users flexibility in controlling the light intensity of LED
’s. MBI5170 guarantees to endure maximum 17V at the
output ports. Besides, the high clock frequency up to 25 MHz also satisfies the system requirements of high
volume data transmission.
By means of the Share-I-O
™ technique, MBI5170 adds new functionality on the pins LE and OE of MBI5168 to
provide an additional function, Current Gain Control, without any extra pins. Thus, MBI5170 could be a drop-in
replacement of MBI5168. The printed circuit board originally designed for MBI5168 may be also applied to
MBI5170. In MBI5170 there are two operation modes and three phases: Normal Mode phase, Mode Switching
transition phase, and Current Adjust Mode phase. The signal on the multi-function pin OE /SW would be monitored.
Once a one-clock-wide short pulse appears on the pin OE /SW, MBI5170 would enter the Mode Switching phase.
At this moment, the voltage level on the pin LE/MOD/CA is used for determining the next mode to which MBI5170
is going to switch.
In the Normal Mode phase, MBI5170 has similar functionality to MBI5168. The serial data could be transferred into
MBI5170 via the pin SDI, shifted in the Shift Register, and go out via the pin SDO. The LE/MOD/CA can latch the
serial data in the Shift Register to the Output Latch. OE /SW would enable the output drivers to sink current.
On the other hand, the Current Adjust Mode phase allows users to adjust the output current level by setting a
run-time programmable Configuration Code. The code is sent into MBI5170 via the pin SDI. The positive pulse of
LE/MOD/CA would latch the code in the Shift Register into a built-in 8-bit Configuration Latch, instead of the Output
Latch. The code would affect the voltage at the terminal R-EXT and control the output current regulator. The output
current could be adjusted finely by a current gain ranging from (1/12) to (127/128) in 256 steps. Hence, the current
skew between IC
’s can be compensated within less than 1% and this feature is suitable for white balancing in LED
color display panels.
Pin Assignment
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