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| 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 5A Stand-by Current 3) Built-in Power On Reset 4) Ghost key rejection Absolute maximum ratings (Ta=25) Item Supply Voltage*1 Input voltage Storage temperature range Package power *1 *2 Symbol VDD VI Tstg PD Value -0.3 ~ +4.5 -0.3 ~ VDD +0.3 -55 ~ +125 272 *2 *1 Unit V V mW comment This IC is not designed to be X-ray proof. 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 Supply voltage rangeVDD Input voltage range Operating temperature range External clock External resistor Symbol Min VDD VIN Topr Fclk Rxi 2.20 -0.2 -30 0.8 118.8 Typ 3.30 25 1.0 120 Max 3.60 VDD+0.2 +85 1.2 121.2 V V MHz k CLKSEL=VDD To Xi pin, when CLKSEL=VSS Unit Condition www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 1/12 2009.09 - Rev.A BU1851GUW Package Specification Technical Note U1851 Lot No. Fig.1 Package SpecificationVBGA035W040 www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 2/12 2009.09 - Rev.A BU1851GUW Pin Assignment Technical Note 1 A TESTM0 2 XRST 3 XO 4 XI 5 ROW0 6 TESTM3 B CLKSEL VDD VDD ROW2 ROW1 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 DiagramTop View Block Diagram XO VDD TESTM[3:0] KINT KSCL KSDA 3wire Control XI CLKSEL Oscillator 8bit Column Drive 8bit COL[7:0] Key Encoder Key Scan 3wire Timeout XRST PORENB VSS Power On Reset Reset Gen 8bit Row Monitor 8bit ROW[7:0] Fig.3 Functional Block Diagram www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 3/12 2009.09 - Rev.A BU1851GUW Pin-out Functional Descriptions Technical Note PIN name VDD VSS XRST CLKSEL XI XO KINT KSCL KSDA ROW0 ROW1 ROW2 ROW3 ROW4 ROW5 ROW6 ROW7 COL0 COL1 COL2 COL3 COL4 COL5 COL6 COL7 PORENB TESTM0 TESTM1 TESTM2 TESTM3 *1 I/O I I I O O I I/O I I I I I I I I O O O O Function Power supply (Core, I/O) GND ResetLow Active 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. Test pin*1 Key Interrupt Clock for serial interface Serial data inout for serial interface Init I I I L H I I Cell Type A B G C C A D Row input from key matrix (Pull-up) I Pull-up E Column output to key matrix O O O O I I I I I Test Pin *2 L C Power on reset enable (Low Active) I B I F Note: This pin must be open in normal operation. *2 Note: All these pins must be tied down to GND in normal operation. www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 4/12 2009.09 - Rev.A BU1851GUW Technical Note A B C D E F G Fig.4 Equivalent IO circuit diagram www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 5/12 2009.09 - Rev.A BU1851GUW Functional Description Technical Note 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 KSDA Start bit invalid Bit7 Bit6 Bit5 Bit0 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. www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 6/12 2009.09 - Rev.A BU1851GUW Power Mode KINT Operating state Technical Note Stand-by state 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". www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 7/12 2009.09 - Rev.A BU1851GUW Technical Note 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 M COL0 B M COL1 B M COL2 B M COL3 B M COL4 B M COL5 B M COL6 B M COL7 B 0x88 0x87 0x08 0x86 0x07 0x85 0x06 0x84 0x05 0x83 0x04 0x82 0x03 0x81 0x02 0x01 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: Make Key (the code when the key is pressed) B: Break Key (the code when the key is released) www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 8/12 2009.09 - Rev.A BU1851GUW Technical Note 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 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 www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 9/12 2009.09 - Rev.A BU1851GUW 3wire Interface AC characteristics Technical Note State START BIT 7 BIT 6 BIT 0 "0" tLOW;INT tSU;STA KINT tHIGH;CLK 1/fSCLK tLOW;CLK KSCL KSDA tSU;DAT tHD;STA tHD;DAT Fig.9 3wire interface AC timing tHD;INTE VDD=3.30VTopr=25, CLKSEL=H (Sysclk = External Clock) Item KSCL Clock Frequency START Condition Setup Time START Condition Hold Time KSCL Low Time KSCL High Time Data Setup Time Data Hold Time KINT End Hold Time KINT Low Time Symbol fSCLK tSU;STA tHD;STA tLOW;CLK tHIGH;CLK tSU;DAT tHD;DAT tHD;INTE tLOW;INT Min 0.030 20 23 23 tHIGH;CLK - (1/Sysclk)x12 (1/Sysclk)x10 (1/Sysclk)x3 500 Typ Max 21.5 500 tHIGH;CLK - (1/Sysclk)x10 (1/Sysclk)x12 (1/Sysclk)x5 1200 Unit kHz ms s s s s s s Condition ms www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 10/12 2009.09 - Rev.A BU1851GUW Application circuit example Technical Note 2.8V 0.1uF VSS TESTM[3:0] PORENB CLKSEL VDD 120k XRST XI COL7 COL6 COL5 COL4 MPU INT XO open KINT COL3 COL2 COL1 SCL SDA KSCL KSDA COL0 BU1851GUW ROW0 ROW1 ROW2 ROW3 ROW4 ROW5 ROW6 ROW7 Fig. 10 Application circuit example www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 11/12 2009.09 - Rev.A BU1851GUW Ordering part number Technical Note B U 1 Part No. 8 5 1 G U W - E 2 Part No. Package GUW: VBGA035W040 Packaging and forming specification E2: Embossed tape and reel VBGA035W040 1PIN MARK 4.0 0.1 Tape 0.9MAX. 4.0 0.1 Embossed carrier tape (with dry pack) 2500pcs E2 The direction is the 1pin of product is at the upper left when you hold Quantity Direction of feed S 0.75 0.1 35- 0.2950.05 0.05 M S AB A P=0.5x5 0.5 B F E D C B A 123456 P=0.5x5 0.75 0.1 0.08 S 0.10 ( reel on the left hand and you pull out the tape on the right hand ) 1pin Direction of feed (Unit : mm) Reel Order quantity needs to be multiple of the minimum quantity. www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. 12/12 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 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/ www.rohm.com (c) 2009 ROHM Co., Ltd. All rights reserved. R0039A |
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