Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
LED Driver IC
PT6955
DESCRIPTION
PT6955 is an LED Controller driven on a 1/4 to 1/7 duty factor. Twelve/nine segment output lines, 4 to
7 grid output lines, one display memory, control circuit are all incorporated into a single chip to build a
highly reliable peripheral device for a single chip microcomputer. Serial data is fed to PT6955 via a
three-line serial interface. Housed in a 24-pin SOP, PT6955’s pin assignments and application circuit
are optimized for easy PCB Layout and cost saving advantages.
FEATURES
•
•
•
•
•
CMOS Technology
Low Power Consumption
8-Step Dimming Circuitry
Serial Interface for Clock, Data Input, Strobe Pins
Available in 24-pin, SOP
APPLICATION
•
Micro-computer Peripheral Device
PT6955 V1.5
-1-
June, 2005
Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
LED Driver IC
PT6955
BLOCK DIAGRAM
PT6955 V1.5
-2-
June, 2005
Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
LED Driver IC
PT6955
INPUT/OUTPUT PORT CONFIGURATION
The schematic diagrams of the input and output circuit of the logic section are shown below.
Input Pins: CLK, STB & DIN
Output Pins: SG10/GR7, SG11/GR6, SG12/GR5
VDD
GND
GND
Output Pins: GR1 to GR4
VDD
Output Pins: SG1 to SG9
VDD
GND
GND
PT6955 V1.5
-3-
June, 2005
Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
LED Driver IC
PT6955
PIN CONFIGURATION
PIN DESCRIPTION
Pin Name
OSC
DIN
CLK
STB
VDD
SG1 ~ SG9
SG10/GR7 ~ SG12/GR5
GND
GR4 ~ GR1
I/O
I
I
I
I
-
O
O
-
O
Description
Pin No.
Oscillator Input Pin
A resistor is connected to this pin to determine
1
the oscillation frequency
Data Input Pin
This pin inputs serial data at the rising edge of the
2
shift clock (starting from the lower bit)
Clock Input Pin
3
This pin reads serial data at the rising edge.
Serial Interface Strobe Pin
The data input after the STB has fallen is processed
4
as a command. When this pin is "HIGH", CLK is ignored.
Power Supply
5, 18
Segment Output Pins
6 ~ 14
(p-channel, open drain)
Segment Output Pin/Grid Output Pin
15 ~ 17
(CMOS Output)
Ground Pin
19, 24
Grid Output Pins (n-channel, open drain)
20 ~ 23
PT6955 V1.5
-4-
June, 2005
Tel: 886-2-66296288
Fax: 886-2-29174598
URL: http://www.princeton.com.tw
LED Driver IC
PT6955
FUNCTION DESCRIPTION
COMMANDS
A command is the first byte (b0 to b7) inputted to PT6955 via the DIN Pin after STB Pin has changed
from “HIGH” to “LOW” State. If for some reason the STB Pin is set to “HIGH” while data or commands
are being transmitted, the serial communication is initialized, and the data/commands being
transmitted are considered invalid.
COMMAND 1: DISPLAY MODE SETTING COMMANDS
PT6955 provides 4 display mode settings as shown in the diagram below: As stated earlier a command
is the first one byte (b0 to b7) transmitted to PT6955 via the DIN Pin when STB is “LOW”. However, for
these commands, Bit No. 3 to Bit No.6 (b2 to b5) are ignored, Bit No.7 & Bit No.8 (b6 to b7) are given
a value of “0”.
The Display Mode Setting Commands determine the number of segments and grids to be used (1/4 to
1/7 duty, 12 to 9 segments). When these commands are executed, the display is forcibly turned off.
A display command “ON” must be executed in order to resume display. If the same mode setting is
selected, no command execution is take place, therefore, nothing happens.
When Power is turned “ON”, the 7-Grid, 9-Segment Mode is selected.
MSB
0
0
-
-
-
-
LSB
b1 b0
Not Relevant
Display Mode Settings:
00: 4 digits, 12 segments
01: 5 digits, 11 segments
10: 6 digits, 10 segments
11: 7 digits, 9 segments
PT6955 V1.5
-5-
June, 2005
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