ROHM BU1851GUW Data Sheet
Summary
Monitor key inputs efficiently with this advanced Key Encoder IC, designed to monitor up to an 8x8 matrix of keys. It significantly reduces CPU load by encoding only changes in key status rather than all states. The manual provides comprehensive details on its operation, including power modes, pin assignments, and low-power features like standby current and ghost key rejection. Ideal for embedded system designers creating general electronic devices such as AV equipment, office automation tools, or consumer amusement products.
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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 5A Stand-by Current 3) Built-in Power On Reset 4) Ghost key rejection
●Absolute maximum ratings (Ta=25℃)
Item Symbol Value Unit comment
Supply Voltage*1 VDD -0.3 ~ +4.5 V Input voltage VI -0.3 ~ VDD +0.3*1 V Storage temperature range Tstg -55 ~ +125 ℃ Package power PD 272*2 m W This IC is not designed to be X-ray proof. *1 It is prohibited to exceed the absolute maximum ratings even including +0.3 V. *2 Package dissipation will be reduced each 2.72m W/ o C when the ambient temperature increases beyond 25 o C.
●Operating Conditions
Limit
Item Symbol Unit Condition
Min Typ Max
Supply voltage range（VDD） VDD 2.20 3.30 3.60 V
Input voltage range VIN -0.2 - VDD+0.2
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
www.rohm.com 2009.09 - Rev.A 1/12 © 2009 ROHM Co., Ltd. All rights reserved.
Page Summary Contents For ROHM BU1851GUW Data Sheet
Manual Details
| Brand | ROHM |
|---|---|
| Pages | 13 |
| File Size | 283.71 KB |
| Published | July 10, 2026 |
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Frequently Asked Questions
What is the maximum number of keys this encoder can monitor?
It can monitor up to 64 keys using an 8x8 matrix.
How does the device enter a low-power state?
The device enters Power Down when XRST=”Low”, which invalidates key encoding and the 3wire interface.
What is the recommended operating voltage range (VDD)?
The supply voltage requirement for operation (VDD) ranges from 2.20 V to 3.60 V.
Can this product be used in critical systems like aerospace or medical equipment?
No, it is not designed for equipment requiring an extremely high level of reliability, such as medical instruments or transportation machinery.