ROHM BU21024FV-M Technical data

A

Touch Screen Controller ICs

Resistive Type Touch Screen Controller ICs

BU21023GUL, BU21023MUV, BU21024FV-M

●Description

Unlike most resistive touch screen controllers, the BU21023/ BU21024 4-wire resistive touch screen controllers enable dual-touch detection and gesture recognition. These intelligent controllers expose a set of registers to a host processor and are software configurable. The controllers can detect single point coordinates, dual coordinates, pinch, spread, rotate left and rotate right gestures, enabling pan and zoom operations in applications that previously had to rely exclusively on capacitive touch technology. Resistive touch does not require custom panel development which reduces development cost and results in faster time to market across a family of products.

●Features

1) Enables single touch, dual touch & gesture recognition using standard 4-wire resistive touch panels

2) Adjustable touch detection threshold allows fine tuning of pressure sensitivity for an application

3) Enables measurement of single point touch pressure

4) SPI and I

5) Programmable interrupt polarity

6) 10-bit ADC provides sufficient resolution for finger or stylus inputs

7) Firmware for internal CPU may be downloaded from Host processor or from an EEPROM

8) Includes filtering options to eliminate false coordinates

9) Built in support for intelligent calibration

10) Easy to swap X & Y coordinates or adapt to different touch panel connections

11) Single 3V power supply

12) Available in a range of small package sizes and temperature ranges

13) Ideally suited for large volume automotive, consumer and industrial applications

●Application ・Products with a LCD that can benefit from pan and zoom operations. ・Smart phones, Digital Cameras, Video Cameras, GPS Receivers, Printers, Copiers, automotive navigation panels, touch kiosks ・Tablet PCs , Notebook computers, LCD displays (with USB interface)

●Line up matrix

2

C like interface for interfacing to host processor

No.11105EAT01

Parameter BU21023GUL BU21023MUV BU21024FV-M

Screen

Maximum detection point

Integrated Filter process

Gesture Detection

Supplied Voltage Range(V)

Temperature Range(℃)

Host I/F

PKG

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4-wire resistive

touch screen

2 2 2

Yes Ye s Yes

2.7 － 3.6 2.7 － 3.6 2.7 － 3.6

-20 － 85 -20 － 85 -40 － 85

4-wire SPI

2-wire serial

VCSP50L2 VQFN028V5050 SSOP-B28

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4-wire resistive

touch screen

4-wire SPI

2-wire serial

4-wire resistive

touch screens

4-wire SPI

2-wire serial

2011.08 - Rev.

A

BU21023GUL,BU21023MUV,BU21024FV-M

●Absolute Maximum Ratings

Parameter Symbol Ratings Unit Condition

Power supply voltage VDD -0.3 ～ 4.5 V

Input voltage VIN VSS-0.3 ～ VDD+0.3 V

*1

BU21023GUL

mW

830

Technical Note

Power dissipation

BU21023MUV 704

Pd

BU21024FV-M 850

*2

mW

*3

mW

Storage temperature range Tstg -50 ～ 125 ℃

*1 Derate by 7.04 mW /℃ centigrade when ambient temperature exceeds 25℃. Measured using Epoxy-Glass PCB measuring 50x58x1.75 mm *2 Derate by 8.30mW /℃ centigrade when ambient temperature exceeds 25℃. Measured using Epoxy-Glass PCB measuring 50x58x1.75mm *3 Derate by 8.50mW /℃ centigrade when ambient temperature exceeds 25℃. Measured using Epoxy-Glass PCB measuring 50x58x1.75mm

●Recommended Operating Conditions

Parameter Symbol

Min. Typ. Max.

Ratings

Unit Condition

Power supply voltage VDD 2.70 3.00 3.60 V

Digital core power supply DVDD 1.62 1.80 1.98 V DVDD_EXT=H

BU21023GUL

Operating temperature range

Note: The BU21023/BU21024 controllers can be operated with a single 3V VDD supply. It is also possible to supply 1.8V DVDD from an external source if the DVDD_EXT pin is connected to logic high.

BU21023MUV

Topr

BU21024FV-M -40 25 85 ℃

-20 25 85 ℃

●Electrical Characteristics (Ta=25℃, VDD=3.00V)

Parameter Symbol

Min. Typ. Max.

Limits

Unit Condition

Low-level input voltage

High-level input voltage

Low-level output voltage

High-level output voltage

Standby current

Sleep current1

Sleep current2

Operating current

Oscillation frequency

Resolution

Differential non-linearity error

Integral non-linearity error

VIL VSS-0.5 - 0.2×VDD V

VIH 0.8×VDD - VDD+0.5 V

VOL - - VSS+0.4 V

VOH VDD-0.4 - - V

Ist - - 1 µA

Icc1 - 60 100 µA

Icc2 - 10 20 µA

Idd - 4 6 mA

Freq 18 20 22 MHz

Ad 1024×1024 Bit

DNL -3.0 - +3.0 LSB

INL -3.0 - +3.0 LSB

RSTB=L

DVDD_EXT=L

DVDD_EXT=H

No load

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BU21023GUL,BU21023MUV,BU21024FV-M

●HOST-I/F mode (4-wire SPI) (SCK=SCL_SCK, SI=SDA_SI, CSB=SEL_CSB, SO=SO)

Technical Note

Condition : VDD = 3.0V Ta=25

Parameter Symbol

CSB setup time t1 30 - - ns

SCK "H" level period t2 30 - - ns

SCK "L" level period t3 30 - - ns

SI setup time t4 20 - - ns

SI holding time t5 20 - - ns

CSB holding time t6 20 - - ns

CSB "H" level time t7 50 - - ns

Data output delay time t8 - - 15 ns

SCK frequency t9 - - 15 MHz

Note: SPI interface is selected by tying IFSEL pin to logic low. IFSEL= logic high selects the 2-wire interface

℃

Limits

Min. Typ. Max.

Unit Condition

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BU21023GUL,BU21023MUV,BU21024FV-M

Technical Note

●HOST-I/F mode (2-wire serial) (SCL=SCL_SCK, SDA=SDA_SI)

The 2-wire serial mode presents an I conforming to the I

2

C specification. The BU21023MUV/ BU21023GUL / BU21024FV-M devices can co-exist with other I2C

2

C like interface for all practical purposes, but it is not a complete implementation

devices on the same bus. The slave address for 2-wire serial communication is 5Ch or 5Dh. This is determined by the SEL_CSB pin.

SEL_CSB = “L” : Slave address = 5Ch SEL_CSB = “H” : Slave address = 5Dh

t

SU;STO

SDA

SCL

t

HD;STA

t

SU;DAT

t

HD;DAT

Address ACK

Data Data

ACK

Parameter Symbol

SCL clock frequency

START condition hold time

SCL “L”

SCL “H”

Data hold time

Data setup time

STOP condition setup time

Min. Typ. Max.

f

0 - 400 kHz

SCL

t

0.6 - - µs

HD:STA

t

1.3 - - µs

LOW

t

0.6 - - µs

HIGH

t

0.1 - - µs

HD:DAT

t

0.1 - - µs

SU:DAT

t

0.6 - - µs

SU:STO

Limits

Unit Condition

・Write protocol

S SLAVE ADDRESS W

7bit = 5Ch or 5Dh 8bit 8bit

A

REGISTER

ADDRESS

A WRITE DATA AP

・Read protocol

S SLAVE ADDRESS W

7bit = 5Ch or 5Dh 8bit 7bit = 5Ch or 5Dh 8bit

from master to slave S = START condition

R = data direction READ (SDA HIGH)

W = data direction WRITE (SDA LOW)

A = acknowledge (SDA LOW)

N = not acknowledge (SDA HIGH)

from slave to master P = STOP condition

A

REGISTER

ADDRESS

A S SLAVE ADDRESS R A READ DATA N P

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BU21023GUL,BU21023MUV,BU21024FV-M

A

A AAA A

A

●EEPROM I/F BU21023/BU21024 controllers include an EEPROM interface for firmware download. Device address of EEPROM is set via register 0x51(EEPROM_ADDR).

Timing chart

t

HD;STA

SDA

t

SU;DAT

SCL

Technical Note

t

SU;STO

t

HD;DAT

SCL clock frequency

START hold time

SCL ”L” width

SCL ”H” width

Data hold time

Data setup time

STOP setup time

Protocol

*IC does not support the write command. *IC supports the following read command.

Start

Address

Parameter Symbol

Read /Write

ACK

Min. Typ. Max.

f

270 310 350 kHz

SCL

t

0.7 - 0.9 µs

HD:STA

t

1.4 - 1.8 µs

LOW

t

1.4 - 1.8 µs

HIGH

t

0.7 - 0.9 µs

HD:DAT

t

0.7 - 0.9 µs

SU:DAT

t

0.7 - 0.9 µs

SU:STO

Data Data

Limits

ACK

Unit Condition

ACK

S

SLAVE

DDRESS

W

1st WORD

DDRESS

DATA(n-3)

2nd WORD

DDRESS

DATA(n-2)

DATA(0)

DATA(n-1)

DATA(n) P

N

Stop

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BU21023GUL,BU21023MUV,BU21024FV-M

●Background Information A resistive touch panel is made up of a multilayer sandwich of resistive films and protective coatings all sitting on top of an LCD display. Resistive touch panels work by direct contact of a stylus or a finger flexing a pair of resistive films, hence any blunt pointing instrument or a gloved finger may be used.

Touch panel resolution The resolution of a touch panel is typically measured in dots per inch (dpi) and is a function of the physical size of the touch panel and the ADC used in the conversion circuitry. For example, a 3”x5” panel used with the BU21023/BU21024 devices can provide a theoretical resolution of 1024 /5 = 204 dpi. In the case of resistive touch panels, the direct contact nature of its operation and finger thickness often impose an upper limit on the effective system resolution that may be achieved, regardless of the resolution of the ADC itself.

●Functional Description

The BU21023/BU21024 devices connect to a standard 4-wire resistive touch screen on one side and to a host processor on the other side. The BU21024 includes four additional sense terminals allowing it to be used with either 4-wire or 8-wire resistive touch screens. The BU21023/BU21024 include the analog and digital circuitry to process and provide dual touch coordinate data and pinch, spread, rotate-right and rotate-left gesture information to the host CPU.

The BU21023/BU21024 devices include an internal CPU and provide a high degree of programmability by exposing a set of registers that can be accessed by a host CPU through SPI or I SPI or I via registers. When an interrupt occurs, for example, due to touch detection, the host processor is required to read an interrupt status register to determine the cause of the interrupt and take appropriate action.

The program memory of the internal CPU may be initialized via the host interface or via an external EEPROM. This is selected by a register setting.

The BU21023/BU21024 devices support two sensing modes; continuous and interval sensing modes, that are register selectable. In the continuous sensing mode, the embedded CPU reads Z, X & Y coordinates continuously when a touch is detected. The interval sensing mode allows a delay to be inserted between each cycle. The continuous sensing mode is used more often though the interval sensing mode minimizes power consumption. The continuous sensing mode typically completes a sampling cycle consisting of Z, X & Y measurements in approximately 2.3 mS.

The BU21023/BU21024 devices enable optimization of touch detection threshold for a given panel. They also include several sophisticated calibration algorithms.

This document includes a description of the registers followed by flow charts that describe specific steps that a host processor must follow. Often, a flow chart requires other flow charts to explain the steps in finer detail.

The document also includes information on touch screen parameters that one should to look for while selecting resistive touch panels for multi-touch.

2

C like interface is selected, The BU21023/BU21024 devices include an INT pin whose polarity can be programmed

2

C like serial interfaces. The IFSEL pin determines whether

Technical Note

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ROHM BU21024FV-M Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual