BU1851GUW_技术文档

GPIO ICs Series

Key Encoder IC

BU1851GUW

No.09098EAT03

●Description

Key Encoder IC can monitor up to 8x8 matrix (64 keys), which means to be adaptable to Qwerty keyboard. We adopt the

architecture that the information of the only key which status is changed, like push or release, is encoded into the 8 bits

data. This can greatly reduce the CPU load which tends to become heavier as the number of keys increase.

(Previously, all key's status is stored in the registers.)

Furthermore, auto sleep function contribute to low power consumption, when no keys are pressed. It is also equipped with

the various functions such as ghost key rejection, N-key Rollover, Built-in power on reset and oscillator.

●Features

1) Monitor up to 64-matrix keys

2) Under 5A Stand-by Current

3) Built-in Power On Reset

4) Ghost key rejection

●Absolute maximum ratings

(Ta=25℃)

Item

Supply Voltage^*1

Input voltage

Symbol

Value

-0.3 ~ +4.5

-0.3 ~ VDD +0.3^*1

-55 ~ +125

272^*2

Unit

V

comment

VDD

VI

V

Storage temperature range

Package power

Tstg

PD

℃

mW

This IC is not designed to be X-ray proof.

^*1It is prohibited to exceed the absolute maximum ratings even including +0.3 V.

^*2Package dissipation will be reduced each 2.72mW/ ^oC when the ambient temperature increases beyond 25 ^oC.

●Operating Conditions

Limit

Typ

Item

Symbol

Unit

Condition

Min

2.20

-0.2

Max

3.60

Supply voltage range（VDD）

VDD

V_IN

3.30

-

V

Input voltage range

VDD+0.2

Operating temperature range

Topr

-30

25

+85

℃

External clock

Fclk

Rxi

0.8

1.0

1.2

MHz

CLKSEL=VDD

External resistor

118.8

120

121.2

kΩ

To Xi pin, when CLKSEL=VSS

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2009.09 - Rev.A

1/12

Technical Note

BU1851GUW

● Package Specification

U1851

Lot No.

Fig.1 Package Specification（VBGA035W040）

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2009.09 - Rev.A

2/12

Technical Note

BU1851GUW

● Pin Assignment

1

2

3

4

5

6

TESTM0

XRST

XO

XI

ROW0

TESTM3

A

B

C

D

E

F

CLKSEL

VDD

VSS

VDD

PORENB

VSS

ROW2

ROW4

ROW6

COL0

COL1

ROW1

ROW3

KINT

KSDA

VDD

VSS

ROW5

KSCL

COL6

COL7

COL4

COL5

COL2

ROW7

TESTM1

COL3

TESTM2

Fig.2 Pin Diagram（Top View）

● Block Diagram

XO

XI

CLKSEL

VDD

Oscillator

TESTM[3:0]

Column

Drive

COL[7:0]

8bit

KINT

KSCL

KSDA

3wire

Control

Key

Encoder

Key Scan

3wire

Timeout

Row

8bit

Monitor

ROW[7:0]

Reset

Gen

XRST

Power

On

Reset

PORENB

VSS

Fig.3 Functional Block Diagram

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2009.09 - Rev.A

3/12

Technical Note

BU1851GUW

● Pin-out Functional Descriptions

Cell

Type

PIN name

I/O

Function

Init

VDD

VSS

-

I

Power supply (Core, I/O)

GND

-

I

-

XRST

Reset（Low Active）

A

H: External clock is used

L: Internal CR oscillator is used

External clock input when “CLKSEL” is H.

120k is attached up to VDD when “CLKSEL”

is L.

CLKSEL

XI

I

B

G

XO

O

Test pin^*1

L

C

KINT

Key Interrupt

H

KSCL

KSDA

ROW0

I

I/O

I

Clock for serial interface

I

A

D

Serial data inout for serial interface

ROW1

ROW2

ROW3

ROW4

ROW5

ROW6

ROW7

COL0

I

Row input from key matrix

(Pull-up)

I

E

Pull-up

I

O

I

COL1

COL2

COL3

Column output to key matrix

L

C

COL4

COL5

COL6

COL7

PORENB

TESTM0

TESTM1

TESTM2

TESTM3

Power on reset enable (Low Active)

Test Pin^*2

I

B

F

I

^*1Note: This pin must be open in normal operation.

^*2Note: All these pins must be tied down to GND in normal operation.

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2009.09 - Rev.A

4/12

Technical Note

BU1851GUW

C

D

A

E

B

F

G

Fig.4 Equivalent IO circuit diagram

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2009.09 - Rev.A

5/12

Technical Note

BU1851GUW

● Functional Description

1. Power mode

The device enters the state of Power Down when XRST=”Low”. When XRST=High after powered, the device enters the standby

state.

Power On Reset

A Power On Reset logic is implemented in this device. Therefore, it will operate correctly even if the XRST port is not used.

In this case, the XRST port must be connected to high (VDD), and the PORENB port must be connected to low (VSS). If

you don’t want to use Power On reset, you must connect PORENB port to high (VDD).

Power Down State

The device enters Power Down state by XRST=”Low”. An internal circuit is initialized, and key encoding and 3wire interface

are invalid. Power On Reset becomes inactive during this state.

Stand-by State

The device enters the stand-by state by setting XRST to "High". In this state, the device is waiting for keys pressed.

When a key is pressed, the state will change to operation. Power On Reset is active in this state if PORENB = low.

Operating State

The device enters the operating state by pressing keys. The device will scan the key matrix and encode the key code,

and then the 3wire interface tries to start communication by driving KINT “Low”. See sec.2 for the details. After

communicating with host device, when no keys are pressed, the device returns to the stand-by state. Power On

Reset is active in this state if PORENB=low.

2. 3wire Interface

KINT

KSCL

invalid

Bit7

Bit6

Bit5

Bit0

KSDA

Start bit

sent by host device

sent by BU1851

Fig.5 Protocol

Figure 5 shows the protocol of BU1851. BU1851 protocol basically consists of 3 wire configuration (KINT, KSCL, and

KSDA) as shown above. Note that this 3wire interface is completely different from I2C and other standard bus interface.

Procedure

1. When BU1851 detects key events, KINT interrupt is generated to host with driving Low.

2. After the host detects KINT interrupt, the host is supposed to send start bit.

3. After BU1851 detects start bit, the 8bit data (key code) transmission on KSDA will start synchronized with the rising

edge of KSCL clock signal, which is sent from the host.

4. 8 bit data are followed by “0” (9^thbit is always “0”), and then BU1851 drives High on KINT line.

timeout

Fig.6 shows the 3wire timeout sequence. It is suppose to happen when Host doesn’t response anything in a certain time.

1. bu1851 generates KINT interrupt.

2. But Host doesn’t response within 500ms.

3. BU1851 stops KINT, and tries to communicate again by generating KINT.

4. BU1851 will go into the stand-by state when the communication fails five times.

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2009.09 - Rev.A

6/12

Technical Note

BU1851GUW

Power

Mode

Operating state

Stand-by state

KINT

start again

5 times fail -->

state will change to stand-by

communication doesn't establish.

(Host doesn't response within 500ms)

Fig.6 3wire timeout

See also “3wire interface AC characteristics”.

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2009.09 - Rev.A

7/12

Technical Note

BU1851GUW

3. Key code Assignment

Table 1 shows the key code assignment. These key codes are sent through KSDA line corresponding to the pushed or released

keys as indicated in section 2.

Table.1 Key code

ROW0

0x01

0x81

0x02

0x82

0x03

0x83

0x04

0x84

0x05

0x85

0x06

0x86

0x07

0x87

0x08

0x88

ROW1

0x11

0x91

0x12

0x92

0x13

0x93

0x14

0x94

0x15

0x95

0x16

0x96

0x17

0x97

0x18

0x98

ROW2

0x21

0xA1

0x22

0xA2

0x23

0xA3

0x24

0xA4

0x25

0xA5

0x26

0xA6

0x27

0xA7

0x28

0xA8

ROW3

0x31

0xB1

0x32

0xB2

0x33

0xB3

0x34

0xB4

0x35

0xB5

0x36

0xB6

0x37

0xB7

0x38

0xB8

ROW4

0x41

0xC1

0x42

0xC2

0x43

0xC3

0x44

0xC4

0x45

0xC5

0x46

0xC6

0x47

0xC7

0x48

0xC8

ROW5

0x51

0xD1

0x52

0xD2

0x53

0xD3

0x54

0xD4

0x55

0xD5

0x56

0xD6

0x57

0xD7

0x58

0xD8

ROW6

0x61

0xE1

0x62

0xE2

0x63

0xE3

0x64

0xE4

0x65

0xE5

0x66

0xE6

0x67

0xE7

0x68

0xE8

ROW7

0x71

0xF1

0x72

0xF2

0x73

0xF3

0x74

0xF4

0x75

0xF5

0x76

0xF6

0x77

0xF7

0x78

0xF8

M

B

COL0

COL1

COL2

COL3

COL4

COL5

COL6

COL7

M

B

M

B

M

B

M

B

M

B

M

B

M

B

M: Make Key (the code when the key is pressed)

B: Break Key (the code when the key is released)

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2009.09 - Rev.A

8/12

Technical Note

BU1851GUW

4. Ghost Key Rejection

Ghost key is an inevitable phenomenon as long as key-switch matrices are used. When three switches located at the corners of

a certain matrix rectangle are pressed simultaneously, the switch that is located at the last corner of the rectangle (the ghost

key) also appears to be pressed, even though the last key is not pressed. This occurs because the ghost key switch is

electrically shorted by the combination of the other three switches (Fig.7). Because the key appears to be pressed electrically, it

is impossible to distinguish which key is the ghost key and which key is pressed. The BU1851 solves the ghost key problem to

use the simple method. If BU1851 detects any three-key combination that generates a fourth ghost key, and BU1851 does not

report anything, indicating the ghost keys are ignored. This means that many combinations of three keys are also ignored when

pressed at the same time. Applications requiring three-key combinations (such as <Ctrl><Alt><Del>) must ensure that the three

keys are not wired in positions that define the vertices of a rectangle (Fig. 8). There is no limit on the number of keys that can be

pressed simultaneously as long as the keys do not generate ghost key events.

PRESSED KEY

EVENT

GHOST-KEY

EVENT

KEY-SWITCH MATRIX

Fig.7 Ghost key phenomenon

EXAMPLES OF VALID THREE-KEY COMBINATIONS

KEY-SWITCH MATRIX

Fig.8 Valid three key combinations

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2009.09 - Rev.A

9/12

Technical Note

BU1851GUW

● 3wire Interface AC characteristics

State

BIT 0

START

BIT 7

BIT 6

"0"

tLOW;INT

tSU;STA

tHD;INTE

KINT

tHIGH;CLK

1/fSCLK

tLOW;CLK

KSCL

KSDA

tSU;DAT

tHD;DAT

tHD;STA

Fig.9 3wire interface AC timing

VDD=3.30V，Topr=25℃, CLKSEL=H (Sysclk = External Clock)

Item

Symbol

f_SCLK

Min

-

Typ

-

Max

21.5

Unit

kHz

Condition

KSCL Clock Frequency

START Condition

Setup Time

START Condition

Hold Time

t_SU;STA

t_HD;STA

0.030

20

-

500

ms

-

s

ms

KSCL Low Time

KSCL High Time

Data Setup Time

Data Hold Time

KINT End Hold Time

KINT Low Time

t_LOW;CLK

t_HIGH;CLK

t_SU;DAT

23

t_HIGH;CLK

–

t_HIGH;CLK–

(1/Sysclk)x10

(1/Sysclk)x12

t_HD;DAT

t_HD;INTE

t_LOW;INT

(1/Sysclk)x10

(1/Sysclk)x3

500

(1/Sysclk)x12

(1/Sysclk)x5

1200

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2009.09 - Rev.A

10/12

Technical Note

BU1851GUW

● Application circuit example

2.8V

0.1uF

COL7

COL6

COL5

COL4

COL3

COL2

COL1

COL0

120kΩ

XRST

XI

XO

MPU

open

INT

KINT

SCL

SDA

KSCL

KSDA

ROW0

ROW1

ROW2

ROW3

ROW4

ROW5

ROW6

ROW7

Fig. 10 Application circuit example

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2009.09 - Rev.A

11/12

Technical Note

BU1851GUW

●Ordering part number

B

U

1

8

5

1

G U W

-

E

2

Part No.

Package

Packaging and forming specification

E2: Embossed tape and reel

GUW:

VBGA035W040

4.0 ± ±0.1

1PIN MARK

Tape

Embossed carrier tape (with dry pack)

Quantity

2500pcs

E2

Direction

of feed

The direction is the 1pin of product is at the upper left when you hold

reel on the left hand and you pull out the tape on the right hand

(

)

S

0.08

S

A

P=0.5×5

0.5

0.75 ± ±0.1

φ

35- 0.295± 0.05

F

φ

M

0.05

S AB

B

E

D

C

B

A

Direction of feed

1pin

1

2 3 4 5 6

Reel

(Unit : mm)

Order quantity needs to be multiple of the minimum quantity.

∗

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2009.09 - Rev.A

12/12

Notice

N o t e s

No copying or reproduction of this document, in part or in whole, is permitted without the

consent of ROHM Co.,Ltd.

The content speciﬁed herein is subject to change for improvement without notice.

The content speciﬁed herein is for the purpose of introducing ROHM's products (hereinafter

"Products"). If you wish to use any such Product, please be sure to refer to the speciﬁcations,

which can be obtained from ROHM upon request.

Examples of application circuits, circuit constants and any other information contained herein

illustrate the standard usage and operations of the Products. The peripheral conditions must

be taken into account when designing circuits for mass production.

Great care was taken in ensuring the accuracy of the information speciﬁed in this document.

However, should you incur any damage arising from any inaccuracy or misprint of such

information, ROHM shall bear no responsibility for such damage.

The technical information speciﬁed herein is intended only to show the typical functions of and

examples of application circuits for the Products. ROHM does not grant you, explicitly or

implicitly, any license to use or exercise intellectual property or other rights held by ROHM and

other parties. ROHM shall bear no responsibility whatsoever for any dispute arising from the

use of such technical information.

The Products speciﬁed in this document are intended to be used with general-use electronic

equipment or devices (such as audio visual equipment, ofﬁce-automation equipment, commu-

nication devices, electronic appliances and amusement devices).

The Products speciﬁed in this document are not designed to be radiation tolerant.

While ROHM always makes efforts to enhance the quality and reliability of its Products, a

Product may fail or malfunction for a variety of reasons.

Please be sure to implement in your equipment using the Products safety measures to guard

against the possibility of physical injury, ﬁre or any other damage caused in the event of the

failure of any Product, such as derating, redundancy, ﬁre control and fail-safe designs. ROHM

shall bear no responsibility whatsoever for your use of any Product outside of the prescribed

scope or not in accordance with the instruction manual.

The Products are not designed or manufactured to be used with any equipment, device or

system which requires an extremely high level of reliability the failure or malfunction of which

may result in a direct threat to human life or create a risk of human injury (such as a medical

instrument, transportation equipment, aerospace machinery, nuclear-reactor controller,

fuel-controller or other safety device). ROHM shall bear no responsibility in any way for use of

any of the Products for the above special purposes. If a Product is intended to be used for any

such special purpose, please contact a ROHM sales representative before purchasing.

If you intend to export or ship overseas any Product or technology speciﬁed herein that may

be controlled under the Foreign Exchange and the Foreign Trade Law, you will be required to

obtain a license or permit under the Law.

Thank you for your accessing to ROHM product informations.

More detail product informations and catalogs are available, please contact us.

ROHM Customer Support System

http://www.rohm.com/contact/

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R0039

A


型号：	BU1851GUW
厂家：	ROHM
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BU1851GUW [ROHM]

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