3

Standard ICs

BU2879AK

Pin No.

Pin

Name

I / O

Function

14, 38

Power supply pin 1

Oscillation pin

Ground pin

Input

Input / output

Input

Connected to system power supply.

OSC

Capacitor connection pin for oscillation

44

Connected to system ground.

7, 43

Serial data input

Input

SI

Serial data input starting from MSB

6

Serial clock input

Input

SCK

Serial data read at rising edge.

8

Serial chip select

Input

CS

Serial initialization when LOW, valid at HIGH.

9

High-voltage withstand

Output pin for segment; output is

output pin for segment

Output

Pch open drain + pull-down resistance.

S1 ~ S11

15 ~ 25

Power supply pin 2

Input

Pull-down resistance connection for FLP driver output.

27

High-voltage withstand

Output pin for grid; output is Pch

output pin for grid

Output

open drain + pull-down resistance.

G1 ~ G10

42 ~ 39,

37 ~ 32

High-voltage withstand

S12 / G15

Used to switch output between segment and grid;

26,

output pin for segment / grid

Output

output is Pch open drain + pull-down resistance.

S16 / G11

28 ~ 31

Key data input pin

Data input pin for key scanning.

Input

K1 ~ K4

10 ~ 13

General-purpose input pin; input data can be

General-purpose input pin

Input

transmitted serially to microcomputer.

SW1 ~ SW4

1 ~ 4

Serial data output

Output

SO

Serial data output starting from MSB;

output is Nch open drain.

5

Parameter

Symbol

Conditions

Supply current

44-pin attachment, at 1000pF oscillation

Input threshold voltage

Pins 1 to 4, 6, 8, 9 to 13

Input current

Pins 1 to 4, 6, 8, 9 to 13

OSC oscillation frequency

44-pin attachment, at 1000pF oscillation

Segment output current

Grid output current

Leakage current when OFF

Output pull-down resistance

Pins 15 to 26, 28 to 37

Maximum operating frequency

Design guarantee value

〈Serial transmission〉

Input data hold

Input data setup

Output data delay

Input clock cycle

Input clock "H" width

Min.

—

1.5

—

130

6

18

—

35

—

0.16

0.16

—

0.5

40

Typ.

—

—

—

200

—

—

—

70

—

—

—

—

—

—

Max.

5

3.5

10

300

—

—

10

140

1

—

—

0.3

—

60

Unit

mA

V

µA

kHz

mA

mA

µA

k

Ω

MHz

µs

µs

µs

µs

%

At minimum input clock cycle

Measurement

circuit

Fig.1

Fig.4

Fig.2

Fig.3

Fig.2

Fig.2

Fig.2

Fig.2

Fig.3

—

—

—

—

—

—

—

—

—

when grid output is specified, grid current is output.