ROHM BU1851GUW

GPIO ICs Series
Key Encoder IC
No.09098EAT03
BU1851GUW
●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
Symbol
VDD
Unit
-0.3 ~ +4.5
VI
Storage temperature range
Tstg
-0.3 ~ VDD +0.3
V
℃
-55 ~ +125
*2
PD
comment
V
*1
Input voltage
Package power
Value
272
mW
This IC is not designed to be X-ray proof.
*1
*2
It is prohibited to exceed the absolute maximum ratings even including +0.3 V.
Package dissipation will be reduced each 2.72mW/ oC when the ambient temperature increases beyond 25 oC.
●Operating Conditions
Limit
Item
Symbol
Unit
Condition
Min
Typ
Max
VDD
2.20
3.30
3.60
V
VIN
-0.2
-
VDD+0.2
V
Operating temperature range
Topr
-30
25
+85
℃
External clock
Fclk
0.8
1.0
1.2
MHz
CLKSEL=VDD
External resistor
Rxi
118.8
120
121.2
kΩ
To Xi pin, when CLKSEL=VSS
Supply voltage range(VDD)
Input voltage range
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© 2009 ROHM Co., Ltd. All rights reserved.
1/12
2009.09 - Rev.A
Technical Note
BU1851GUW
● Package Specification
U1851
Lot No.
Fig.1 Package Specification(VBGA035W040)
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2/12
2009.09 - Rev.A
Technical Note
BU1851GUW
● Pin Assignment
A
1
2
3
4
5
6
TESTM0
XRST
XO
XI
ROW0
TESTM3
CLKSEL
VDD
VDD
ROW2
ROW1
B
C
KINT
VDD
VSS
PORENB
ROW4
ROW3
D
KSDA
VDD
VSS
VSS
ROW6
ROW5
E
KSCL
COL6
COL4
COL2
COL0
ROW7
F
TESTM1
COL7
COL5
COL3
COL1
TESTM2
Fig.2 Pin Diagram(Top View)
● Block Diagram
XO
XI
CLKSEL
VDD
Oscillator
TESTM[3:0]
KINT
KSCL
3wire
Control
8bit
Column
Drive
8bit
COL[7:0]
8bit
Row
Monitor
8bit
ROW[7:0]
Key
Encoder
KSDA
Key Scan
3wire
Timeout
Reset
Gen
XRST
PORENB
Power
On
Reset
VSS
Fig.3 Functional Block Diagram
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3/12
2009.09 - Rev.A
Technical Note
BU1851GUW
● Pin-out Functional Descriptions
I/O
Function
Init
Cell
Type
VDD
-
Power supply (Core, I/O)
-
-
VSS
-
GND
-
-
XRST
I
Reset(Low Active)
I
A
I
B
I
G
PIN name
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
I
XI
I
XO
O
Test pin*1
L
C
KINT
O
Key Interrupt
H
C
KSCL
I
Clock for serial interface
I
A
KSDA
I/O
Serial data inout for serial interface
I
D
ROW0
I
ROW1
I
ROW2
I
ROW3
I
I
I
Pull-up
E
ROW4
Row input from key matrix
(Pull-up)
ROW5
I
ROW6
I
ROW7
I
COL0
O
COL1
O
COL2
O
COL3
O
Column output to key matrix
L
C
COL4
O
COL5
O
COL6
O
COL7
O
PORENB
I
Power on reset enable (Low Active)
I
B
TESTM0
I
TESTM1
I
I
F
TESTM2
I
TESTM3
I
*2
Test Pin
*1
Note: This pin must be open in normal operation.
*2
Note: All these pins must be tied down to GND in normal operation.
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4/12
2009.09 - Rev.A
Technical Note
BU1851GUW
A
B
C
E
F
G
D
Fig.4 Equivalent IO circuit diagram
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5/12
2009.09 - Rev.A
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
KSDA
Bit7
Bit6
Bit5
Bit0
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.
th
4. 8 bit data are followed by “0” (9 bit 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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6/12
2009.09 - Rev.A
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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7/12
2009.09 - Rev.A
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
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW7
M
0x01
0x11
0x21
0x31
0x41
0x51
0x61
0x71
B
0x81
0x91
0xA1
0xB1
0xC1
0xD1
0xE1
0xF1
M
0x02
0x12
0x22
0x32
0x42
0x52
0x62
0x72
B
0x82
0x92
0xA2
0xB2
0xC2
0xD2
0xE2
0xF2
M
0x03
0x13
0x23
0x33
0x43
0x53
0x63
0x73
B
0x83
0x93
0xA3
0xB3
0xC3
0xD3
0xE3
0xF3
M
0x04
0x14
0x24
0x34
0x44
0x54
0x64
0x74
B
0x84
0x94
0xA4
0xB4
0xC4
0xD4
0xE4
0xF4
M
0x05
0x15
0x25
0x35
0x45
0x55
0x65
0x75
B
0x85
0x95
0xA5
0xB5
0xC5
0xD5
0xE5
0xF5
M
0x06
0x16
0x26
0x36
0x46
0x56
0x66
0x76
B
0x86
0x96
0xA6
0xB6
0xC6
0xD6
0xE6
0xF6
M
0x07
0x17
0x27
0x37
0x47
0x57
0x67
0x77
B
0x87
0x97
0xA7
0xB7
0xC7
0xD7
0xE7
0xF7
M
0x08
0x18
0x28
0x38
0x48
0x58
0x68
0x78
B
0x88
0x98
0xA8
0xB8
0xC8
0xD8
0xE8
0xF8
COL0
COL1
COL2
COL3
COL4
COL5
COL6
COL7
M: Make Key (the code when the key is pressed)
B: Break Key (the code when the key is released)
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8/12
2009.09 - Rev.A
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
KEY-SWITCH MATRIX
Fig.8 Valid three key combinations
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9/12
2009.09 - Rev.A
Technical Note
BU1851GUW
● 3wire Interface AC characteristics
State
START
BIT 7
BIT 0
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
Min
Typ
Max
Unit
KSCL Clock Frequency
fSCLK
-
-
21.5
kHz
tSU;STA
0.030
-
500
ms
tHD;STA
20
-
-
s
KSCL Low Time
tLOW;CLK
23
-
-
s
KSCL High Time
tHIGH;CLK
23
-
-
s
Data Setup Time
tSU;DAT
tHIGH;CLK –
(1/Sysclk)x12
-
tHIGH;CLK –
(1/Sysclk)x10
s
Data Hold Time
tHD;DAT
(1/Sysclk)x10
-
(1/Sysclk)x12
s
KINT End Hold Time
tHD;INTE
(1/Sysclk)x3
-
(1/Sysclk)x5
s
KINT Low Time
tLOW;INT
500
-
1200
ms
START Condition
Setup Time
START Condition
Hold Time
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10/12
Condition
2009.09 - Rev.A
Technical Note
BU1851GUW
● Application circuit example
2.8V
XRST
COL7
COL6
XI
COL5
XO
MPU
CLKSEL
120kΩ
VSS
TESTM[3:0]
PORENB
VDD
0.1uF
open
COL4
INT
COL3
KINT
COL2
COL1
KSCL
SDA
KSDA
COL0
BU1851GUW
SCL
ROW0
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW7
Fig. 10 Application circuit example
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11/12
2009.09 - Rev.A
Technical Note
BU1851GUW
●Ordering part number
B
U
1
Part No.
8
5
1
G
Part No.
U
W
Package
GUW:
VBGA035W040
-
E
2
Packaging and forming specification
E2: Embossed tape and reel
VBGA035W040
<Tape and Reel information>
4.0 ± 0.1
35- φ 0.295±0.05
φ 0.05 M S AB
A
P=0.5×5
0.5
F
E
D
C
B
A
Embossed carrier tape (with dry pack)
Quantity
2500pcs
Direction
of feed
E2
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
B
P=0.5×5
0.08 S
0.75 ± 0.1
Tape
0.75 ± 0.1
0.10
0.9MAX. 4.0 ± 0.1
1PIN MARK
1pin
1 2 3 4 5 6
(Unit : mm)
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Reel
12/12
Direction of feed
∗ Order quantity needs to be multiple of the minimum quantity.
2009.09 - Rev.A
Notice
Notes
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, communication 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
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