Datasheet
Resistive touch screen controller LSI series for Automotive
4-wire Resistive
Touch Screen Controller
BU21028FV-M
General Description
Key Specifications
Unlike most resistive touch screen controllers, the
BU21028FV-M 4-wire resistive touch-screen controller
can generate data that enables dual touch detection.
The Host processor can use this data to detect single
and dual point coordinates.
Features
(Note 1)
2.7V to 3.6V
-40°C to +85°C
1.0 μA(Max)
100 μA(Max)
0.8 mA(Typ)
12bit
W(Typ) x D(Typ) x H(Max)
Package(s)
AEC-Q100
standard 4-wire resistive touch screens
Single and dual touch detection
I2C-like interface (for the host processor I/F)
12-bit resolution
Single 2.7V to 3.6V power supply
Auto power down/on control
Built-in clock oscillator circuit
(Note1: Grade 3)
Power supply voltage:
Temperature range:
Standby current:
Sleep current:
Operating current:
Coordinate resolution:
SSOP-B20
6.50 mm x 6.40 mm x 1.15 mm
Applications
Equipment with built-in user interface for 4-wire
resistive touch screen
■ Portable information equipment like smart phones,
tablets, and PDAs
■ PCs or peripheral equipment like laptops, touch
screen monitors, and printers
■ audioIn-vehicle terminals such as car navigation
system, car audio system and display audio
systems
■
1.0uF
option(*1)
10ohm
Y+
2.2kohm
2.2kohm
DVDD_IN
Host IO VDD
VREF
DVDD
_OUT
0.1uF
VDD
VDDP
VDD
1.0uF
Typical Application Circuit(s)
option(*4)
XP
RSTB
33ohm
XN
SCL
33ohm
SDA
33ohm
1.0nF
10ohm
1.0nF
X+
10ohm
YP
1.0nF
10ohm
Y-
YN
Host
(GPIO port）
33ohm
INT
option(*2)
1.0nF
AUX
AD0
option(*3)
Option(*1) For the touch panel noise reduction
(Please choose the fixed valuse to environment, a demand)
Option(*2) Please connect to VDD, when use as Slave address = 41h
Option(*3) For ESD protection (Zener diode / TVS diode)
Option(*4) Damping resistance
(Please choose the fixed valuse to environment, a demand)
〇Product structure : Silicon monolithic integrated circuit
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AD1
GND
4- wire
resistive
touch
screen
BU21028FV-M
GNDP
X-
〇This product has no designed protection against radioactive rays
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BU21028FV-M
Contents
General Description ........................................................................................................................................................................ 1
Features.......................................................................................................................................................................................... 1
Applications .................................................................................................................................................................................... 1
Key Specifications........................................................................................................................................................................... 1
Package(s)...................................................................................................................................................................................... 1
Typical Application Circuit(s) ........................................................................................................................................................... 1
Pin Configuration(s) ........................................................................................................................................................................ 3
Pin Description(s) ........................................................................................................................................................................... 3
Equivalent Circuit ............................................................................................................................................................................ 3
Block Diagram(s) ............................................................................................................................................................................ 4
OVERVIEW .................................................................................................................................................................................... 4
Absolute Maximum Ratings ............................................................................................................................................................ 5
Thermal Resistance
(Note 1)
............................................................................................................................................................... 5
Recommended Operating Conditions ............................................................................................................................................. 6
Electrical Characteristics................................................................................................................................................................. 6
Host interface AC timing ................................................................................................................................................................. 7
Host Interface Specification ............................................................................................................................................................ 8
Power Supply and Reset Timing Specification .............................................................................................................................. 12
Specification of Touch Detection ................................................................................................................................................... 13
Control Flow Chart ........................................................................................................................................................................ 14
Coordinates Data Calculation ....................................................................................................................................................... 20
Register Description ..................................................................................................................................................................... 23
Operational Notes ......................................................................................................................................................................... 28
Ordering Information ..................................................................................................................................................................... 30
Marking Diagrams ......................................................................................................................................................................... 30
Physical Dimension, Tape and Reel Information ........................................................................................................................... 31
Revision History ............................................................................................................................................................................ 32
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Pin Configuration(s)
Pin Description(s)
Pin Description(s)
(TOP VIEW)
GNDP
1
20
YN
AD0
2
19
XN
(NC)
3
18
YP
AD1
4
17
XP
SDA
5
16
AUX
SCL
6
15
VDDP
INT
7
14
DVDD_OUT
RSTB
8
13
(NC)
DVDD_IN
9
12
VREF
VDD
10
11
GND
Pin
No
1
Pin
Name
GNDP
I/O
Description
Equivalent
circuit
-
Ground for touch screen drivers
A
2
AD0
I
Slave address input bit0
3
(NC)
-
- (Note4)
-
4
AD1
I
Test input (Note1)
A
5
SDA
I/O
Serial data (Note2)
C
6
SCL
I
C
7
INT
O
8
RSTB
I
9
DVDD_IN
-
10
VDD
-
Serial clock (Note2)
Interrupt output.
Pin polarity with active low.
System reset
Regulator input for control logic.
(Note3)
Power supply
11
GND
-
-
12
VREF
-
13
(NC)
-
14
DVDD_OUT
-
15
VDDP
-
16
AUX
I
Ground
Regulator input for control logic.
(Note3)
- (Note4)
Regulator output for control logic.
(Note3)
Power supply for
touch screen drivers.
Auxiliary channel input
D
17
XP
I/O
XP channel input
D
18
YP
I/O
YP channel input
D
19
XN
I/O
XN channel input
D
20
YN
I/O
YN channel input
D
B
A
-
(Note1) Connect AD1 to GND.
(Note2) SCL and SDA need a pull-up resistor greater than 2.2kΩ.
(Note3) Bypass VREF, DVDD_IN, DVDD_OUT to GND with a 1.0uF capacitor
and do not connect to the supply.
(Note4) Non-connect internal. Please connect to GND or OPEN.
Equivalent Circuit
PAD
PAD
Figure A.
Figure B.
PAD
PAD
Figure C.
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Figure D.
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BU21028FV-M
Block Diagram(s)
VDDP
VDD
PVDD
LDO
DVDD
LDO
DVDD
_OUT
VREF DVDD_IN
OSC
PENIRQ
XP
XN
YP
Touch
Screen
Drivers
& I/F
M
SAR
ADC
U
YN
X
Control
Logic
&
2 wire
Serial
I/F
INT
SDA
SCL
AD0
AD1
AUX
RSTB
GNDP
GND
OVERVIEW
BU21028FV-M is a controller for 4-wire resistive touch screens. It has built-in 12-bit SAR A/D converter, clock oscillator, and
LDO regulator for internal blocks and operates with 2.7 to 3.6V single power supply. Aside from being able to detect single
point coordinates and touch pressure like existing 4-wire resistive touch screen controllers can, it can also detect dual
coordinates by generating data based on the prearranged touch screen parameters.
Host interface
Communication between BU21028FV-M controller and the host processor uses 2-wire serial interface. The
BU21028FV-M, being the I2C slave device, is controlled by the host processor by writing to its registers. This way, the
host processor sets whether the touch screen controller operates under command control mode or under automatic
control mode. In automatic control mode, the host processor reads the touch data saved by the controller in its internal
registers at any time.
Preprocess
A/D conversion is continuously done for several times in one driving time. Data is median average processed; meaning
data is sorted and calculation that takes the average from the center of the sorted data is performed.
Interrupt control
The BU21028FV-M sends an interrupt signal to the host processor through INT terminal, an active-low pin, whenever it
detects touch on the screen. In automatic control mode, this happens after the scan of the first touch is completed.
2-point detection function
The 2-point detection function of BU21028FV-M can be used by calibrating the circuit for 2-point detection based on the
inherent panel perimeters (registers 0x3, 0x4). Since the characteristics of each touch panel differ significantly, it is
necessary for the host processor to execute the calibration of parameters to match the 2-point detection circuit of
BU21028FV-M with every touch panel.
Auto power-down, power-on function(Power control)
After a conversion function has been completed, the BU21028FV-M automatically powers down in order to reduce current
consumption. In automatic control mode, scanning restarts automatically from power down when the touch screen is
operated.
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Absolute Maximum Ratings
Parameter
Symbol
Rating
Unit
Conditions
Power supply voltage
VDD
-0.3 to 4.5
V
Power supply voltage for
touch screen
VDDP
-0.3 to 4.5
V
Digital input voltage
VIN1
-0.3 to VDD+0.3
V
AD0,AD1,SDA,
SCL and RSTB
AUX input voltage
VIN2
GND-0.3 to 2.5
V
AUX
Voltage input to
touch screen Interface
VIN3
GND-0.3 to 2.5
V
XP,YP,XN
and YN
Storage temperature range
Tstg
-50 to 125
℃
Caution: Operating the IC over the absolute maximum ratings may damage the IC. The damage can either be a short circuit between pins or an open circuit
between pins and the internal circuitry. Therefore, it is important to consider circuit protection measures, such as adding a fuse, in case the IC is operated over
the absolute maximum ratings.
Thermal Resistance
(Note 1)
Parameter
Symbol
Thermal Resistance (Typ)
1s
(Note 3)
(Note 4)
2s2p
Unit
SSOP-B20
Junction to Ambient
Junction to Top Characterization Parameter
(Note 2)
θJA
115.4
57.3
°C/W
ΨJT
10
8
°C/W
(Note 1)Based on JESD51-2A(Still-Air)
(Note 2)The thermal characterization parameter to report the difference between junction temperature and the temperature at the top center of the outside
surface of the component package.
(Note 3)Using a PCB board based on JESD51-3.
Layer Number of
Measurement Board
Single
Material
Board Size
FR-4
114.3mm x 76.2mm x 1.57mmt
Top
Copper Pattern
Thickness
Footprints and Traces
70μm
(Note 4)Using a PCB board based on JESD51-7.
Layer Number of
Measurement Board
4 Layers
Material
Board Size
FR-4
114.3mm x 76.2mm x 1.6mmt
Top
2 Internal Layers
Bottom
Copper Pattern
Thickness
Copper Pattern
Thickness
Copper Pattern
Thickness
Footprints and Traces
70μm
74.2mm x 74.2mm
35μm
74.2mm x 74.2mm
70μm
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Recommended Operating Conditions
Parameter
Rating
Symbol
Min
Typ
Max
Unit
Power supply voltage
VDD
2.7
3.0
3.6
V
Power supply voltage for
touch screen
VDDP
2.7
-
VDD
V
Tj
-40
25
85
℃
Operating temperature
Electrical Characteristics
Conditions
VDD≧VDDP
(Unless otherwise specified Tj=25℃, VDD=VDDP=3.00V, GND=0.00V)
Parameter
Symbol
Rating
Min
Typ
Max
Unit
Conditions
Low-level output voltage1
VOL1
-
-
GND+0.4
V
AD0,AD1,SDA,SCL and
RSTB
AD0,AD1,SDA,SCL and
RSTB
SDA(IL=5mA),INT(IL=3mA),
High-level output voltage1
VOH1
VDD-0.4
-
-
V
INT,IL=-3mA
Standby current
Ist
-
-
1.0
uA
RSTB=L
Sleep current
Islp
-
100
200
uA
RSTB=H
Active current
Iact
-
0.8
2.0
mA
No Load
+3
LSB
Low-level input voltage
VIL
GND-0.3
-
VDD*0.2
V
High-level input voltage
VIH
VDD*0.8
-
VDD+0.3
V
Resolution
Ad
Differential non-linearity error
DNL
Integrate non-linearity error
Switch on-resistance
12
-3
-
Bit
INL
-5
-
+5
LSB
RON
0.5
5.0
20.0
Ω
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Host interface AC timing
The slave address for 2-wire serial interface is selectable from “40h” or “41h” by “AD0” input.
AD0 = “L” : Slave Address = 40h
AD0 = “H” : Slave Address = 41h
tHD_STA
tSU_DAT
tHD_DAT
tSU_STA
tHD_STA
tSU_STO
tBUF
SDA
tLOW
tHIGH
tR
tF
SCL
START
CONDITION
REPEATED
START
CONDITION
STOP
CONDITION
START
CONDITION
2-wire serial I/F AC timing characteristics (Tj=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted)
PARAMETER
SCL clock frequency
Hold time for (repeated) START condition
Low period of SCL
High period of SCL
Setup time for repeated START condition
Data hold time
Data setup time
Rise time for both SCL and SDA
Fall time for both SCL and SDA
Setup time for STOP condition
Bus free time between a STOP
and START condition
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fSCL
tHD_STA
tLOW
tHIGH
tSU_STA
tHD_DAT
tSU_DAT
tR
tF
tSU_STO
MIN
0
0.6
1.3
0.6
0.6
0
0.1
0.6
RATING
TYP
-
MAX
400
0.9
300
300
-
tBUF
1.3
-
-
SYMBOL
7/32
UNIT
CONDITION
kHz
us
us
us
us
us
us
ns
ns
us
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BU21028FV-M
Host Interface Specification
The BU21028FV-M controller operates as an I2C slave device. At the start of the communication, it receives an address
byte transmitted by the host processor and then then sends back an acknowledgement byte. The host processor can
transmit a command to execute conversion or to access registers only after receiving the acknowledgement for the address
byte. Communication ends when BU21028FV-M receives a stop command.
●Address byte
On the address byte, the slave address for 2-wire interface is written on the upper 7 bits and the READ/WRITE bit is written
on the last bit. The upper six bits of the slave address are fixed to “100000” while the last bit is determined by the “AD0”
input.
Table 1. Serial Interface Slave Address Byte
MSB
D7
1
D6
D5
D4
D3
D2
D1
0
0
0
0
0
A0
LSB
D0
R/W
Bit D1: A0
Slave address bit0 (AD0)
Bit D0: R/W
1=read (reading data)
0=write (writing data)
●Command byte
The operation of BU21028FV-M is dictated by the command byte. The host processor sets CID (D7) to 1 for conversion
function or to 0 for register access.
Table 2. Serial Interface Command Byte 1(CID=1)
MSB
D7
1
D6
D5
D4
D3
CF
D2
D1
CMSK
PDM
LSB
D0
STP
Bit D7: Command Byte ID
1= Command Byte 1(starts the conversion function determined by CF (Bit D6-D3)
Bits D6-D4: CF
Conversion function is selected as detailed below.
Table 3. BU21028FV-M Conversion Function List
CF
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Description
Touch screen scan function: X, Y, Z1 and Z2 coordinates and converted.
NOP
Auxiliary input converted.
Reserved
Free scan function: Drivers status and input of A/D assignment by Host.
Calibration: Parameters which used dual touch detection calibrated.
NOP
NOP
X+, X- drivers status.
Y+, Y- drivers status.
Y+, X- drivers status.
NOP
Touch screen scan function: X coordinate converted.
Touch screen scan function: Y coordinate converted.
Touch screen scan function: Z1 and Z2 coordinates converted.
Reserved
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CF= 0x0 (0000) : Automatic scan
This makes BU21028FV-M periodically and automatically scan the screen and convert data upon detecting touch. When
the device cannot detect touch, it stops and stays in power down state until it detects the next pen-down. The order of scan
process is Z1, Z2, X and Y.
CF= 0x1 (0001), 0x6 (0110), 0x7 (0111), 0xB (1011)
No operation. (“PDM” and “STP” is valid.)
CF = 0x2 (0010)
This converts the voltage impressed to AUX. After the conversion has been completed, the device is powered
down according to the PDM setting.
CF= 0x4 (0100) : Free scan mode
In Free Scan Mode, the driver state (X+, X-, Y+, Y-) and conversion input (X+, X-, Y+, Y-, AUX) can be selected through
register settings.
CF= 0x5 (0101) : Calibration
This calibrates the parameters for dual touch detection. To activate the dual touch function, setting of CF to 0101 and
execution of the calibration command should be done after power-on.
CF= 0x8 (1000), 0x9 (1001), 0xA (1010): Drivers status control
This activates the analog circuit and panel driver corresponding to each command. BU21028FV-M remains in this state until
it receives another SCAN instruction or until "STP" is set.
CF= 0xC (1100), 0xD (1101), 0xE (1110): Manual scan
This converts coordinates that correspond to each command. BU21028FV-M goes to power-down state after a complete
conversion if "PDM" is set to "0". Otherwise, it stays at power-on state.
CF =0x3 (0011), 0xF (1111)
Reserved.
Bit D2：CMSK
0=Executes convert function.
1=Reads the convert result
Bit D1：PDM
Power Down Control
0= Powers down the device after converter function stops
1= Keeps power on after converter function stops
Bit D0：STP
1= Aborts currently running conversion and changes the state to power-down (STP is automatically set to “0”.)
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Table 4. Serial interface Command Byte 0(CID=0)
MSB
D7
0
D6
D5
D4
D3
ADDR[3:0]
D2
D1
PAGE
SWRST
LSB
D0
STP
Bit D7: Command Byte ID
0=Reads/writes on data register addresses specified by ADDR (Bit D6-D3).
Bits D6-D3: ADDR
D2: PAGE
Register addresses that “ADDR” and “PAGE” can access are listed below.
Table 5. BU21028FV-M Register Map
7
6
5
PAGE ADDR INI
0x0
0x20 RSV0
RSV0
CALIB
0
0x1
0xA6
MAV
AVE
0x2
0x04
INTVL_TIME
0x3
0x10
0x4
0x10
0x5
0x10
0x6
0x00
0x7
0x00
0x8
0x00
0x9
0x0F
0xA
0x0F
0xB
0x72
RM8
STRETCH PU90K
0xC
0x00
RSV1
RSV0
0xD
0x00 TEST
AUTO
PDM
1
4
INTRM
3
RSV0
-
2
RSV0
1
RSV0
SMPL
TIME_ST_ADC
0
RSV0
EVR_X
EVR_Y
EVR_XY
RSV0
RSV0
DUAL
RSV0
-
0xE
0xF
0x0
BUSY
RSV0
PIMIR_X
PIMIR_Y
PIDAC_OFS
RSV1
RSV0
ACTIVE
CALIB
_DONE
RSV0
TOUCH
0x02
HW_IDH
0x29
HW_IDL
0x00 SW_YP_ SW_YP_ SW_YN_ SW_YN_ SW_XP_ SW_XP_ SW_XN_ SW_XN_
POW
GND
POW
GND
POW
GND
POW
GND
0x1
0x00 RSV0
RSV0
RSV0 SW_AUX SW_YPM SW_YNM SW_XPM SW_XNM
Reserved
0x2-0x4
DPRM
RSV0
RSV0
RSV0
RSV0
RSV1
RSV1
0x5
0x03 RSV0
RSV0
RSV0
RSV0
RSV0
RSV0
RSV0 EX_TIME_ST
0x6
0x00 RSV0
Reserved
0x7-0xF
-
(*1) RSV0 must be set to 0.
(*2) RSV1 must be set to 1
Bit D1: SWRST
1= Initializes all registers, stops all operations, and changes state to power-down (SWRST is automatically set “0”.)
Bit D0: STP
1= Aborts currently running conversion and changes the state to power-down (STP is automatically set to “0”.)
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●WRITE CYCLE
The host first sends an address byte to the BU21028FV-M controller. This address byte is composed of the 7-bit slave byte
on the upper seven bits and the Read/Write bit on the LSB. If the controller receives a valid address byte, it issues an
acknowledgement. The host processor can transmit a command only after receiving the acknowledgement for the address
byte from the controller. The controller then sends back another acknowledgement, allowing the host to continually send
write data or issue a STOP command.
Write : Convert function
S
Slave address
0
A
Command Byte
C
F
3
1
C
F
2
C
F
1
C
M
S
K
C
F
0
A
P
D
M
P
S
T
P
Write : Register write
S
Slave address
0
A
Command Byte
A
D
R
3
0
S：START condition
A
D
R
2
A
D
R
1
A
D
R
0
P
A
G
E
Data Byte 0
Address = start address
A
S
W
R
S
T
Data Byte N
Address = start address + N
A
A
P
S
T
P
P：STOP condition
A：ACK
N：NACK
Figure 1. Write Protocol
●READ CYCLE
The READ bit is the LSB of the address byte. When read mode is selected, BU21028FV-M sends back the data byte
followed by an acknowledgement to the host. The data sent back is either the conversion result or the register value,
depending on the last command byte received by BU21028FV-M. The host needs to resend the conversion command with
setting "CMSK=1" if it has read the register value before reading the conversion result. BU21028FV-M sends the next data
byte after it has received an acknowledgement from the host for the previous data byte. Upon receiving the last data byte,
the host finishes read access by issuing a START (or STOP) commands followed by NACK (not acknowledged) command.
Read cycle
S
Slave address
1
S：START condition
Data Byte 0
address = start address
A
Data Byte 1
address = start address + 1
A
Data Byte N
address = start address + N
A
N
P
P：STOP condition
A：ACK
N：NACK
Figure 2. Read Protocol
●SCL STRETCH
If the host reads the conversion result while conversion is ongoing, BU21028FV-M notifies it through the SCL_STRETCH
function. (*1) SCL_STRECH is released when conversion function is finished.
SCL
SDA
1
0
0
0
0
0
0
A
C
K
1
D7
D6
Slave address & Read cycle
STATUS
finish
(idle)
Convert function is running
Stretch(SCL=L)
Figure 3. SCL Stretch Timing
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BU21028FV-M
Power Supply and Reset Timing Specification
A power supply sequence and timing AC characters of BU21028FV-M are below.
BU21028FV-M becomes the reset state at RSTB terminal "L" input and the idle state at RSTB terminal "H" input.
In BU21028FV-M, the communication with the host processor becomes active after internal reset release.
After RSTB= "H" input, please start control of BU21028FV-M after (min: 1.0ms) in waiting time of the internal reset release.
～
～
～
Typ. 3.0V
VDD
VDDP
～
When RSTB terminal becomes the L input, and BU21028FV-M becomes the reset state,
the data of all registers and the touch data become initial value.
After having had a reset state, the initialization of the register and power-on sequence is necessary again.
0V
VDD*0.8
VDD*0.8
Trise
RSTB
VDD*0.2
VDD*0.2
0V
Tdelay1
Tdelay2
Power-on-reset AC Timing Characteristics (Tj=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted)
Parameter
Symbol
Rating
Unit
MIN
TYP
MAX
Trise
1
-
10
ms
RSTB rise delay time
Tdelay1
1
-
-
ms
RSTB fall delay time
Tdelay2
0
-
-
ms
VDD rise time
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Condition
TSZ02201-0L5L0F300720-1-2
27.May.2016 Rev.002
BU21028FV-M
Specification of Touch Detection
BU21028FV-M executes its touch detection function by outputting an interrupt signal at pin INT once it is able to detect
touch. The circuit diagram of the touch detection function is shown on the following figure.
VDDP
INT
50kΩ
90kΩ
PU90K
(register)
Connected when touch
screen is touched
Control
Logic
YP
XP
High when XP or YP
dirvers ON
Touch screen
YN
XN
ON
GNDP
GND
Figure 4. Touch detection circuit
When the touch panel is connected to the panel interface terminals (XP, XN, YP, YN), pin XP is connected to VDDP through
an internal pull-up resistor inside the IC and pin YN is connected to GNDP. During a no-touch state, BU21028FV-M will be
on standby. During this time, INT outputs "H" through an internal pull-up resistor. Since pins XP and YN are connected to
the touch screen through contact resistance, the resistance ratio of the internal pull-up resistance and the touch screen
resistance is able to detect the voltage drop at pin XP whenever the screen is touched. This results to an "L" output at INT.
When touch is detected and pins XP and YP is put to drive state by each scanning operation, the internal pull-up resistance
is disconnected from pin XP and the output of pin INT is held at "L".
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TSZ02201-0L5L0F300720-1-2
27.May.2016 Rev.002
BU21028FV-M
Control Flow Chart
BU21028FV-M has two operation modes, the command mode, wherein the device operates under the control of the host
processor, and auto mode, wherein the device operates by automatic control.
In order to use two-point detection, it is necessary to calibrate the circuit for this function by setting the correct state of
registers for panel perimeters (register Addr.0x3, 0x4). Calibration is performed by transmitting the command CF=0101 from
the host processor. Take note that each register should be initialized after power on. Moreover, for two-point detection, the
interrupt signal from the IC should be enabled after performing parameter calibration.
Power-on Sequence flow chart
White box: Control flow
Charcoal gray box: Divergence by the use function
Light gray box: For periodic calibration
Start
Power supply
Reset release
(RSTB = H)
Wait internal reset release
(min. 1ms）
Initialize register
Use 2-points detection
Use only single touch detection
No
Send calibration command
(CF = 0x5)
Count = 0
(For periodic calibration)
Yes
Wait for finish calibration by below way
・Check INT pin
・Check register(CALIB_DONE)
(page=0, addr.=0x0D bit1)
・Wait for more than 10ms
Check INT pin or read status register
Touch detection
No
Yes
Wait
Use Auto mode
No
Yes
Send scan_XYZ command
(CF = 0x0)
Start timer
(For periodic calibration)
Disable interrupt MASK on HOST
SCAN status
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TSZ02201-0L5L0F300720-1-2
27.May.2016 Rev.002
BU21028FV-M
Command Mode
In Command Mode, BU21028FV-M operates totally under the control of the host processor. In order to take touch data, the
host processor needs to control BU21028FV-M when there is touch pressure. Since it is necessary for the host processor to
issue a command in order to get data, the processing of a host interface in between the presence of touch pressure
becomes more active compared with the auto system.
Sensing sequence (Command mode) flow chart
White box: Control flow
Charcoal gray box: Divergence by the use function
Light gray box: For periodic calibration
Start
INT pin = H
(No interrupt)
Interrupt
No
Yes
Count = 0
(For periodic calibration)
Stop timer
(For periodic calibration)
Timer interrupt
Enable interrupt MASK on HOST
No
Yes
X
Z
Stop timer
(For periodic calibration)
Send X-axis drivers status command
(CF = 0x8)
Send Z-way drivers status command
(CF = 0xA)
Periodic calibration
for 2-points detection circuit
X coordinate convert and read
0xE0 (CF = 0xC) Burst-read 4 byte
Z coordinate convert and read
0xF0 (CF = 0xE) Burst-read 4 byte
（Use only single touch case : 2 byte）
（Use only single touch case : 2 byte）
(Need plural data case: repeat dashed X box)
(Need plural data case: repeat dashed Z box)
Y
Use only single touch detection
Send Y-axis drivers status command
(CF = 0x9)
Use 2-points detection
No
Yes
single
coordinate data calculation
2-points
coordinate data calculation
Y coordinate convert and read
0xE8 (CF = 0xD) Burst-read 6 byte
（Use only single touch case : 2 byte）
(Need plural data case: repeat dashed Y box)
INT pin = H
(No interrupt)
No
Yes
Start timer
(For periodic calibration)
Disable interrupt MASK on HOST
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BU21028FV-M
CF=0x5 (0101) Calibration timing chart
HOST
CALIB
(CF=0x5)
Read
Status
INT
tConv1
tConv1
tCalib
tConv1
tConv1
tCalib
Sample and Conversion
for X coordinate
Sample and Conversion
for Y coordinate
Calibrate
parameters
Sample and Conversion
for X coordinate
Sample and Conversion
for Y coordinate
Calibrate
parameters
BU21029
Detecting
touch
Detecting
touch
Figure 5. Calibration Flow
tPON
= 710us
tDLY1
= 1.5us
tADC
= 18us
tDLY2
= 1.0us
tTIME_ST_ADC = register (addr.0x2)
tSMPL
= register (addr.0x1)
tConv1
tCalib
= tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2)
= 1 internal clock
(*1) Even if the part with dashed lines is not performed, read status does not influence the operation.
(*2) Except the first one, tPON(s) is always zero.
Sensing timing chart (command mode)
HOST
Turn On
X+ and XDrivers
(CF=0x8)
Turn On
Y+ and YDrivers
(CF=0x9)
Read
result of
SCAN X
SCAN X
(CF=0xC)
Read
result of
SCAN Y
SCAN Y
(CF=0xD)
INT
tConv1
tConv1
BU21029
Detecting
touch
Waiting for
scan command
Sample and Conversion
for X coordinate
Detecting
touch
Waiting for
scan command
Sample and Conversion
for Y coordinate
Detecting
touch
Figure 6. Touch Screen Scan Flow 1 (X and Y scan)
HOST
Turn On
X+ and YDrivers
(CF=0xA)
Read
result of
SCAN Z1
SCAN Z
(CF=0xE)
Read
result of
SCAN Z2
INT
tConv2
tConv3
BU21029
Detecting
touch
Sample and Conversion
for Z1 coordinate
Waiting for
scan command
Sample and Conversion
for Z2 coordinate
Detecting
touch
Figure 7. Touch screen scan flow 2 (Z1 and Z2 scan)
tPON
= 710us
tDLY1
= 1.5us
tADC
= 18us
tDLY2
= 1.0us
tTIME_ST_ADC = register (addr.0x2)
tSMPL
= register (addr.0x1)
tConv1
tConv2
tConv3
= tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2)
= tPON + tDLY1 + tTIME_ST_ADC + (tADC * tSMPL) + tDLY2
= tDLY1 + (tADC * tSMPL) + tDLY2
(*1) Time is calculated with the oscillating frequency of the internal OSC at 8MHz.
(*2) In case PDM=1, tPON(s) is set to zero except for the first one.
(*3) The dashed part is required only when apply time set for a panel is more than TIME_ST_ADC.
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TSZ02201-0L5L0F300720-1-2
27.May.2016 Rev.002
BU21028FV-M
Auto Mode
In Auto Mode, BU21028FV-M automatically takes all detected touch and pressure data. An interrupt signal for the 1st data
taken is transmitted after detection of touch pressure has been completed. Since BU21028FV-M automatically takes data
whenever touch pressure is detected, the host processor does not need to control the touch screen.
Auto Mode of operation starts when SCAN-XYZ (CF=0000) is received from the host processor. The INT pin is not
concerned with any touch state. It is set to “H” until the 1st touch data from the start of operation is acquired.
Sensing sequence flow chart (Auto mode)
White box: Control flow
Charcoal gray box: Divergence by the use function
Light gray box: For periodic calibration
Start
INT pin = H
(No interrupt)
Interrupt
No
Yes
Count = 0
(For periodic calibration)
Stop timer
(For periodic calibration)
Timer interrupt
No
Yes
Use only single touch detection
Use 2-points detection
No
Yes
Stop timer
(For periodic calibration)
Burst-read 8 byte
Burst-read 14 byte
Periodic calibration
for 2-points detection circuit
single
coordinate data calculation
2-points
coordinate data calculation
INT pin = H
(No interrupt)
Yes
No
INT pin = H
(No interrupt)
No
Yes
Start timer
(For periodic calibration)
Disable interrupt MASK on HOST
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BU21028FV-M
Sensing timing chart (Auto mode)
HOST
Read
result of SCAN XYZ
SCAN XYZ
(CF=0x0)
INT
tConv4
tINTVL
BU21029
Detecting
touch
Z1 coordinate
Sample and Conversion
Z2 coordinate
X coordinate
Y coordinate
Wait (INTVL_TIME)
Sample and Conversion
Z1 coordinate
Z2.
Figure 8. Touch screen scan flow 3 (XYZ scan)
tPON
= 710us
tDLY1
= 1.5us
tADC
= 18us
tDLY2
= 1.0us
tTIME_ST_ADC = register (addr.0x2)
tINTVL
= register (addr.0x2)
tSMPL
= register (addr.0x1)
tConv4
= tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2) * 3
(*1) Time is calculated with the oscillating frequency of the internal OSC is 8MHz.
(*2) In the case of PDM=1, every tPON(s) is zero except for the first one.
(*3) The order of taking each touch data, etc. cannot be changed.
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TSZ02201-0L5L0F300720-1-2
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BU21028FV-M
Calibration sequence flow chart
White box: Control flow
Charcoal gray box: Divergence by the use function
Light gray box: For periodic calibration
From main
Count = Count + 1
Count > 9
No
Yes
Check user interface on system
Use 2-points
operation
Use only 1 point touch or
Unknown
Enable interrupt MASK on HOST
Send STOP command
(STP = 1)
Send calibration command
(CF = 0x5)
Wait for finish calibration by below way
・Check INT pin
・Check register(CALIB_DONE)
(page=0, addr.=0x0D bit1)
・Wait for more than 10ms
Use Auto mode
No
Yes
Send scan_XYZ command
(CF = 0x0)
Return main
(Note) It is not essential about the “Check user interface”. Please carry it out as needed.
(Note) Please adjust the threshold of Count (“Count > 9” above flowchart) depending on a period of periodic calibration.
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BU21028FV-M
Coordinates Data Calculation
The touch position for dual touch is converted to coordinates by the host processor by processing the data which the
BU21028FV-M outputs. The data outputted changes with the commands received from the host processor as shown in
Table1. The host processor should take data from the BU21028FV-M by burst read via I2C. When reception stops and
resumes before all data is taken, data is again outputted from Byte0.
When using only single point detection, it may be the end of reception once each coordinate is taken.
Table 9. The Output Data List of Each Command
X
Y
Z1
0
coordinate
coordinate
coordinate
1
X 2 points
Y 2 points
Z2
2
paramter
paramter
coordinate
3
Ghost
4
Dummy
Dummy
parameter
5
6
7
8
9
10
11
12
13
14
15
-
X coordinate
Y coordinate
Z1 coordinate
Z2 coordinate
X 2 points
paramter
Y 2 points
paramter
Ghost
parameter
Dummy
Table 10. The Output Data Format List
DATA
Bit07
X[11]
Y[11]
Z1[11]
Z2[11]
Bit06
X[10]
Y[10]
Z1[10]
Z2[10]
Bit05
X[9]
Y[9]
Z1[9]
Z2[9]
ByteH
Bit04 Bit03
X[8]
X[7]
Y[8]
Y[7]
Z1[8] Z1[7]
Z2[8] Z2[7]
Bit02
X[6]
Y[6]
Z1[6]
Z2[6]
Bit01
X[5]
Y[5]
Z1[5]
Z2[5]
Bit00
X[4]
Y[4]
Z1[4]
Z2[4]
Bit07
X[3]
Y[3]
Z1[3]
Z2[3]
Bit06
X[2]
Y[2]
Z1[2]
Z2[2]
Bit05
X[1]
Y[1]
Z1[1]
Z2[1]
ByteL
Bit04 Bit03
X[0]
0
Y[0]
0
Z1[0]
0
Z2[0]
0
Bit02 Bit01 Bit00
X coordinate
0
0
0
Y coordinate
0
0
0
Z1 coordinate
0
0
0
Z2 coordinate
0
0
0
X 2 points
PX[9]
PX[8] PX[7] PX[6] PX[5] PX[4] PX[3] PX[2] PX[1] PX[0]
0
0
0
0
0
SPX
parameter
Y 2 points
PY[9]
PY[8] PY[7] PY[6] PY[5] PY[4] PY[3] PY[2] PY[1] PY[0]
0
0
0
0
0
SPY
parameter
Ghost
GH[11] GH[10] GH[9] GH[8] GH[7] GH[6] GH[5] GH[4] GH[3] GH[2] GH[1] GH[0]
0
0
0
SGH
parameter
(*1)The ByteH is the even number Byte. The ByteL is the odd number Byte. It means that X coordinates are ByteH=Byte0 and ByteL=Byte1 when it is taken
with a command method.
X coordinate: Touched coordinate of X. It becomes gravity center coordinate of 2 points at dual touch.
X = ByteH * 16 + ByteL / 16
Y coordinate: Touched coordinate of Y. It becomes gravity center coordinate of 2 points at dual touch.
Y = ByteH * 16 + ByteL / 16
Z1 coordinate: Touched coordinate of Z1. It’s used in calculating touch pressure.
Z1 = ByteH * 16 + ByteL / 16
Z2 coordinate: Touched coordinate of Z2. It’s used in calculating touch pressure.
Z2 = ByteH * 16 + ByteL / 16
X 2-point touch parameter: It is used for 2-point touch detection. It serves as pointer of the lock up table used for x-axis
2-point distance calculation. PX may be set to 0 when SPX is 1because the x-axis 2-point distance becomes 0.
PX = ByteH * 4 + ByteL / 64 (In the case of SPX=0)
PX = 0
(In the case of SPX=1.)
Y 2-point touch parameter: It is used for 2-point touch detection. It serves as pointer of the lock up table used for y-axis
2-point distance calculation. PY may be set to 0 when SPY is 1 because the y-axis 2-point distance becomes 0.
PY = ByteH * 4 + ByteL / 64 (In the case of SPY=0)
PY = 0
(In the case of SPY=1)
Ghost parameter: It is a value for judging a touch position (the direction of inclination) at dual touch.
GH = ByteH * 16 + ByteL / 16 (In the case of SGH=0)
GH = (ByteH * 16 + ByteL / 16) - 4096(In the case of SGH=1)
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BU21028FV-M
Coordinates data calculation flow chart (Using only 1-point case)
From main
X = 0x00[7:0] x 16 + 0x01[7:3] / 16
Y = 0x02[7:0] x 16 + 0x03[7:3] / 16
Z1 = 0x04[7:0] x 16 + 0x05[7:3] / 16
Z2 = 0x06[7:0] x 16 + 0x07[7:3] / 16
( Any filter function )
Post X, Y coordinate
Return main
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BU21028FV-M
Coordinates data calculation flow chart (Using 2-points case)
From main
PRMX1 = data table[PXMAX]
PRMX2 = data table[PX]
X = 0x00[7:0] x 16 + 0x01[7:3] / 16
Y = 0x02[7:0] x 16 + 0x03[7:3] / 16
Z1 = 0x04[7:0] x 16 + 0x05[7:3] / 16
Z2 = 0x06[7:0] x 16 + 0x07[7:3] / 16
DX = 2048 x ( PRMX2 / PRMX1 )
SPX=0 :
PX = 0x08[7:0] x 4 + 0x09[7:6] / 64
SPX=1 :
PX = 0
PRMY1 = data table[PYMAX]
PRMY2 = data table[PY]
DY = 2048 x ( PRMY2 / PRMY1 )
SPY=0 :
PY = 0x0A[7:0] x 4 + 0x0B[7:6] / 64
SPY=1 :
PY = 0
X1 = X + DX
X2 = X - DX
SGH=0 :
GH = 0x0C[7:0] x 16 + 0x0D[7:4] / 16
SGH=1 :
GH = (0x0C[7:0] x 16 + 0x0D[7:4] / 16) - 4096
Clip calculation
X1 < 0 :
X1 = 0
X1 > 4095 :
X1 = 4095
X2 < 0 :
X2 = 0
X2 > 4095 :
X2 = 4095
( Any filter function )
| GH | < TH1
GH ≧ TH3
Y1 = Y + DY
Y2 = Y – DY
GH ＜ TH3
Y1 = Y – DY
Y2 = Y + DY
No
Yes
| PX - PY | < TH2
Clip calculation
Y1 < 0 :
Y1 = 0
Y1 > 4095 :
Y1 = 4095
No
Yes
Y2 < 0 :
Y2 = 0
Y2 > 4095 :
Y2 = 4095
Post X, Y as X1, Y1 coordinate
( 2-points coordinate offset calculation )
Return main
Post X1, Y1, X2, Y2 as 2-points coordinate
*Note:
TH1 : Please decide based on touch screen size or module.
TH2 : Please decide based on touch screen size or module.
TH3 = 0
Return main
PXMAX : decided at panel parameter setting flowchart
PYMAX : decided at panel parameter setting flowchart
(Note) Please refer application note regarding detail of panel parameter setting flowchart, data table TH1, TH2.
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BU21028FV-M
Register Description
Table 12. CFR0 Register (PAGE=0, ADDR=0x0, Reset value=0x20)
D7
RSV0
D6
RSV0
D5
CALIB
D4
INTRM
D3
RSV0
D2
RSV0
D1
RSV0
D0
RSV0
Bits D7-D6, D3-D0: RSV0
Reserved. Set these bits to 0.
Bit D5 : CALIB
Internal parameter setting-1 for calibration of dual touch detection
0= Not to use calibration result
1= Use calibration result
Bit D4 : INTRM
Setting of INT state in case BU21028FV-M is active after conversion by “PDM” setting
0= depend on “pen-down”
1= always output “0”
Table 13. CFR1 Register (PAGE=0, ADDR=0x1, Reset value=0xA6)
D7
D6
D5
D4
D3
D2
D1
MAV
AVE[2:0]
SMPL[2:0]
Bit D7: MAV
Median Average Filter
0= Off
1= On
D0
Bits D6-D4: AVE
AVE+1= The number of average samples setting for MAV. If AVE is greater than SMPL, AVE takes the value of
SMPL.
Bits D2-D0: SMPL
SMPL+1= The number of conversion samples setting for MAV.
Ex. In the case of CFR1 = 0xA6 (the number of average samples is 3 and the number of conversion samples is 7)
Conversion result
{ 1676, 1688, 1656, 1677, 1659, 1702, 4095 }
Sorted result
{ 1656, 1659, 1676, 1677, 1688, 1702, 4095 }
Chose 3 center data
{ 1656, 2.79, 1676, 1677, 1688, 1702, 4095 }
Average above 3 data = (1676 + 1677 + 1688) / 3 =1680 (vs averaged all six data = 2022)
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Table 14. CFR2 Register (PAGE=0, ADDR=0x2, Reset value=0x04)
D7
D6
D5
INTVL_TIME[3:0]
D4
D3
D2
D1
TIME_ST_ADC[3:0]
D0
Bits D7-D4: INTVL_TIME
This sets the waiting time between completion of conversion and start of next conversion.
(Only usable setting at conversion function=0x0.)
If used, set value as four or more.
Table 15. INTVL_TIME setting
value
0x0～0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC～0xF
time
Reserved
0.256ms
1.024ms
2.048ms
4.096ms
5.120ms
8.912ms
10.240ms
15.360ms
20.480ms
※Times shown above are calculated with oscillating frequency of internal OSC at 8MHz.
Bit D3-D0 : TIME_ST_ADC
This sets the waiting time between application of voltage to panel and start of A/D conversion.
Table 16. TIME_ST_ADC Setting
value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
time
EX_TIME_ST=0 EX_TIME_ST=1
10us
20us
30us
40us
50us
60us
70us
80us
90us
100us
200us
250us
300us
350us
400us
450us
0.5ms
0.6ms
0.7ms
0.8ms
0.9ms
1.0ms
1.5ms
2.5ms
3.0ms
4.0ms
5.0ms
6.0ms
7.0ms
8.0ms
9.0ms
10.0ms
※Times shown above are calculated with oscillating frequency of internal OSC at 8MHz.
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Table 17. EVR Register (PAGE=0, ADDR=0x3 to 0x5, Reset value=0x10)
D7
D6
D5
D4
D3
EVR_*[7:0]
D2
D1
D0
Bits D7-D0: EVR_*
This is gain setting 1 for dual touch detection. When using 2-point detection function, it is necessary to set this before
conversion. It corresponds to X, Y and XY (Z). It is not necessary to change EVR_XY from initial value.
Table 18. PIMIR Register (PAGE=0, ADDR=0x9 to 0xA, Reset value=0x0F)
D7
-
D6
-
D5
-
D4
D3
D2
PIMIR_*[4:0]
D1
D0
Bits D4-D0: PIMIR_*
This is gain setting 2 for dual touch detection. It is not necessary to change this from the initial value.
It corresponds to X and Y.
Table 19. CFR3 Register (PAGE=0, ADDR=0xB, Reset value=0x72)
D7
RM8
D6
STRETCH
D5
PU90K
D4
DUAL
D3
D2
D1
PIDAC_OFS[3:0]
D0
Bit D7: RM8
Coordinate resolution setting
0= 12bit
1= 8bit
Bit D6: STRETCH
SCL_STRETCH function setting
0= off
1= on
Bit D5 : PU90K
Internal pull-up resistance for touch detection setting
0= about 50kΩ
1= about 90kΩ
Bit D4: DUAL
Dual touch detection function setting
0= Off
1= On
Bits D3-D0: PIDAC_OFS
Dual touch detection circuit adjustment setting. It is not necessary to change this from initial value.
Table 20. LDO Register (PAGE=0, ADDR=0xC, Reset value=0x00)
D7
-
D6
RSV1
D5
RSV0
D4
RSV0
D3
-
D2
RSV1
D1
RSV0
D0
RSV0
Bit D6 : RSV1
Bit D5-D4 : RSV0
Bit D2 : RSV1
Bit D1-D0 : RSV0
Please set 44h at initialize register in the power on sequence flow chart.
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Table 22. STATUS Register (PAGE=0, ADDR=0xD, Reset value=0x00, Read only)
D7
D6
D5
D4
D3
D2
TEST
AUTO
PDM
-
BUSY
ACTIVE
D1
CALIB
_DONE
D0
TOUCH
Bit D7: TEST
This bit will become “1” during TEST mode.
Bit D6: AUTO
This bit will become “1” at conversion function 0.
Bit D5: PDM
PDM setting value of command byte1
Bit D3: BUSY
st
This bit will become “1” during conversion of 1 coordinate data.
Bit D2: ACTIVE
This bit will become “1” when internal analog circuit is active.
Bit D1: CALIB_DONE
This bit will become “1” in case that dual touch detection parameter adjustment is finished by command (CF=0x5).
This bit will be clear when “1” is written on this bit.
Bit D0: TOUCH
This bit will become “1” when pen-down is internally detected.
Table 23. HW_ID1 Register (PAGE=0, ADDR=0xE, Reset value=0x02, Read only)
D7
D6
D5
D4
D3
HW_IDH
D2
D1
D0
Bits D7-D0: HW_IDH
High 8bit of IC’s ID
Table 24. HW_ID2 Register (PAGE=0, ADDR=0xF, Reset value=0x29, Read only)
D7
D6
D5
D4
D3
HW_IDL
D2
D1
D0
Bits D7-D0: HW_IDL
Low 8-bit of IC’s ID
Table 25. FREE_SW1 Register (PAGE=1, ADDR=0x0, Reset value=0x00)
D7
D6
D5
D4
D3
D2
D1
D0
SW_YP_ SW_YP_ SW_YN_ SW_YN_ SW_XP_ SW_XP_ SW_XN_ SW_XN_
POW
GND
POW
GND
POW
GND
POW
GND
Bits D7-D0: SW_**_POW(GND)
Driver setting at conversion function 4(Free scan)
Drive to “+” by set POW and “-”by set GND, Must not set “+”and“-”to one terminal at the same time.
** = the corresponding terminal name
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Table 26. FREE_SW2 Register (PAGE=1, ADDR=0x1, Reset value=0x00)
D7
RSV0
D6
RSV0
D5
RSV0
D4
D3
D2
D1
D0
SW_AUX SW_YPM SW_YNM SW_XPM SW_XNM
Bits D7 – D5: RSV0
Reserved. They must be set “0”.
Bit D4: SW_AUX
Bit D3-D0: SW_**M
A/D input setting at conversion function 4(Free scan)
** = the corresponding terminal name
Table 27. SPCFG (PAGE=1, ADDR=0x5, Reset value=0x03)
D7
RSV0
D6
DPRM
D5
RSV0
D4
RSV0
D3
RSV0
D2
RSV0
D1
RSV1
D0
RSV1
Bits D7, D5-D2 : RSV0 , Bits D1-D0 : RSV1
RSV0 must be set to 0 and RSV1 must be set to 0
Bit D6: DPRM
2-point touch parameter through mode 0=Off (Normal) 1=On (Through for test).
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Operational Notes
1.
Reverse Connection of Power Supply
Connecting the power supply in reverse polarity can damage the IC. Take precautions against reverse polarity when
connecting the power supply, such as mounting an external diode between the power supply and the IC’s power
supply pins.
2.
Power Supply Lines
Design the PCB layout pattern to provide low impedance supply lines. Furthermore, connect a capacitor to ground at
all power supply pins. Consider the effect of temperature and aging on the capacitance value when using electrolytic
capacitors.
3.
Ground Voltage
Ensure that no pins are at a voltage below that of the ground pin at any time, even during transient condition.
4.
Ground Wiring Pattern
When using both small-signal and large-current ground traces, the two ground traces should be routed separately but
connected to a single ground at the reference point of the application board to avoid fluctuations in the small-signal
ground caused by large currents. Also ensure that the ground traces of external components do not cause variations
on the ground voltage. The ground lines must be as short and thick as possible to reduce line impedance.
5.
Thermal Consideration
Should by any chance the maximum junction temperature rating be exceeded the rise in temperature of the chip may
result in deterioration of the properties of the chip. In case of exceeding this absolute maximum rating, increase the
board size and copper area to prevent exceeding the maximum junction temperature rating.
6.
Recommended Operating Conditions
These conditions represent a range within which the expected characteristics of the IC can be approximately
obtained. The electrical characteristics are guaranteed under the conditions of each parameter.
7.
Inrush Current
When power is first supplied to the IC, it is possible that the internal logic may be unstable and inrush current may
flow instantaneously due to the internal powering sequence and delays, especially if the IC has more than one power
supply. Therefore, give special consideration to power coupling capacitance, power wiring, width of ground wiring,
and routing of connections.
8.
Operation Under Strong Electromagnetic Field
Operating the IC in the presence of a strong electromagnetic field may cause the IC to malfunction.
9.
Testing on Application Boards
When testing the IC on an application board, connecting a capacitor directly to a low-impedance output pin may
subject the IC to stress. Always discharge capacitors completely after each process or step. The IC’s power supply
should always be turned off completely before connecting or removing it from the test setup during the inspection
process. To prevent damage from static discharge, ground the IC during assembly and use similar precautions during
transport and storage.
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Operational Notes – continued
10. Inter-pin Short and Mounting Errors
Ensure that the direction and position are correct when mounting the IC on the PCB. Incorrect mounting may result in
damaging the IC. Avoid nearby pins being shorted to each other especially to ground, power supply and output pin.
Inter-pin shorts could be due to many reasons such as metal particles, water droplets (in very humid environment)
and unintentional solder bridge deposited in between pins during assembly to name a few.
11. Unused Input Pins
Input pins of an IC are often connected to the gate of a MOS transistor. The gate has extremely high impedance and
extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it. The small
charge acquired in this way is enough to produce a significant effect on the conduction through the transistor and
cause unexpected operation of the IC. So unless otherwise specified, unused input pins should be connected to the
power supply or ground line.
12. Regarding the Input Pin of the IC
In the construction of this IC, P-N junctions are inevitably formed creating parasitic diodes or transistors. The
operation of these parasitic elements can result in mutual interference among circuits, operational faults, or physical
damage. Therefore, conditions which cause these parasitic elements to operate, such as applying a voltage to an
input pin lower than the ground voltage should be avoided. Furthermore, do not apply a voltage to the input pins
when no power supply voltage is applied to the IC. Even if the power supply voltage is applied, make sure that the
input pins have voltages within the values specified in the electrical characteristics of this IC.
13. Ceramic Capacitor
When using a ceramic capacitor, determine the dielectric constant considering the change of capacitance with
temperature and the decrease in nominal capacitance due to DC bias and others.
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Ordering Information
B
U
2
1
0
Part Number
2
8
F
V
Package
FV: SSOP-B20
-
ME 2
Product rank
M: Product of Automotive rank
Packaging and forming specification
E2: Embossed tape and reel
Marking Diagrams
BU21028
1pin mark
Lot No.
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Physical Dimension, Tape and Reel Information
Package Name
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Revision History
Date
Revision
13.Jan.2016
001
27.May.2016
002
Changes
New Release
Fix miss description.
P5. Absolute Maximum Ratings (Ta=25℃) -> Absolute Maximum Ratings
P5. Thermal Resistance
2 Internal Layers Copper Pattern : 74.2mm2 (Square) -> 74.2mm x 74.2mm
Bottom Copper Pattern
: 74.2mm2 (Square) -> 74.2mm x 74.2mm
In table : TO252-J5/TO252-3 -> SSOP-B20
P6. (old) Operating temperature Symbol Topr
(new) Operating temperature Symbol Tj
P6. (old) Unless otherwise specified Ta=25℃, VDD=VDDP=3.00V, GND=0.00V
(new) Unless otherwise specified Tj=25℃, VDD=VDDP=3.00V, GND=0.00V
P7. (old) Ta=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted
(new) Tj=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted
P10.RegisterMap PAGE=0, ADDR=0Ch
(old)[6:4]=PVDDLDO_OUT, [2:0]=DVDDLDO_OUT
(new)[6:4]=RSV1, [2:0]= RSV1
P12. (old) Ta=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted
(new) Tj=25℃, VDD=VDDP=3.00V, GND=0.00V, unless otherwise noted
P25.Register Description PAGE=0, ADDR=0Ch
Change to RSV1. Changed comment of setting(below).
(old)
[6:4]=PVDDLDO_OUT, [2:0]=DVDDLDO_OUT
Please set same value to PVDDLDO_OUT and DVDDLDO_OUT.
(new)
[6]=RSV1, [5:4]=RSV0, [2]= RSV1, [1:0]= RSV0
Please set 44h at initialize register in the power on sequence flow chart.
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Notice
Precaution on using ROHM Products
1.
(Note 1)
If you intend to use our Products in devices requiring extremely high reliability (such as medical equipment
,
aircraft/spacecraft, nuclear power controllers, etc.) and whose malfunction or failure may cause loss of human life,
bodily injury or serious damage to property (“Specific Applications”), please consult with the ROHM sales
representative in advance. Unless otherwise agreed in writing by ROHM in advance, ROHM shall not be in any way
responsible or liable for any damages, expenses or losses incurred by you or third parties arising from the use of any
ROHM’s Products for Specific Applications.
(Note1) Medical Equipment Classification of the Specific Applications
JAPAN
USA
EU
CHINA
CLASSⅢ
CLASSⅡb
CLASSⅢ
CLASSⅢ
CLASSⅣ
CLASSⅢ
2.
ROHM designs and manufactures its Products subject to strict quality control system. However, semiconductor
products can fail or malfunction at a certain rate. Please be sure to implement, at your own responsibilities, adequate
safety measures including but not limited to fail-safe design against the physical injury, damage to any property, which
a failure or malfunction of our Products may cause. The following are examples of safety measures:
[a] Installation of protection circuits or other protective devices to improve system safety
[b] Installation of redundant circuits to reduce the impact of single or multiple circuit failure
3.
Our Products are not designed under any special or extraordinary environments or conditions, as exemplified below.
Accordingly, ROHM shall not be in any way responsible or liable for any damages, expenses or losses arising from the
use of any ROHM’s Products under any special or extraordinary environments or conditions. If you intend to use our
Products under any special or extraordinary environments or conditions (as exemplified below), your independent
verification and confirmation of product performance, reliability, etc, prior to use, must be necessary:
[a] Use of our Products in any types of liquid, including water, oils, chemicals, and organic solvents
[b] Use of our Products outdoors or in places where the Products are exposed to direct sunlight or dust
[c] Use of our Products in places where the Products are exposed to sea wind or corrosive gases, including Cl2,
H2S, NH3, SO2, and NO2
[d] Use of our Products in places where the Products are exposed to static electricity or electromagnetic waves
[e] Use of our Products in proximity to heat-producing components, plastic cords, or other flammable items
[f] Sealing or coating our Products with resin or other coating materials
[g] Use of our Products without cleaning residue of flux (even if you use no-clean type fluxes, cleaning residue of
flux is recommended); or Washing our Products by using water or water-soluble cleaning agents for cleaning
residue after soldering
[h] Use of the Products in places subject to dew condensation
4.
The Products are not subject to radiation-proof design.
5.
Please verify and confirm characteristics of the final or mounted products in using the Products.
6.
In particular, if a transient load (a large amount of load applied in a short period of time, such as pulse. is applied,
confirmation of performance characteristics after on-board mounting is strongly recommended. Avoid applying power
exceeding normal rated power; exceeding the power rating under steady-state loading condition may negatively affect
product performance and reliability.
7.
De-rate Power Dissipation depending on ambient temperature. When used in sealed area, confirm that it is the use in
the range that does not exceed the maximum junction temperature.
8.
Confirm that operation temperature is within the specified range described in the product specification.
9.
ROHM shall not be in any way responsible or liable for failure induced under deviant condition from what is defined in
this document.
Precaution for Mounting / Circuit board design
1.
When a highly active halogenous (chlorine, bromine, etc.) flux is used, the residue of flux may negatively affect product
performance and reliability.
2.
In principle, the reflow soldering method must be used on a surface-mount products, the flow soldering method must
be used on a through hole mount products. If the flow soldering method is preferred on a surface-mount products,
please consult with the ROHM representative in advance.
For details, please refer to ROHM Mounting specification
Notice-PAA-E
© 2015 ROHM Co., Ltd. All rights reserved.
Rev.003
Precautions Regarding Application Examples and External Circuits
1.
If change is made to the constant of an external circuit, please allow a sufficient margin considering variations of the
characteristics of the Products and external components, including transient characteristics, as well as static
characteristics.
2.
You agree that application notes, reference designs, and associated data and information contained in this document
are presented only as guidance for Products use. Therefore, in case you use such information, you are solely
responsible for it and you must exercise your own independent verification and judgment in the use of such information
contained in this document. ROHM shall not be in any way responsible or liable for any damages, expenses or losses
incurred by you or third parties arising from the use of such information.
Precaution for Electrostatic
This Product is electrostatic sensitive product, which may be damaged due to electrostatic discharge. Please take proper
caution in your manufacturing process and storage so that voltage exceeding the Products maximum rating will not be
applied to Products. Please take special care under dry condition (e.g. Grounding of human body / equipment / solder iron,
isolation from charged objects, setting of Ionizer, friction prevention and temperature / humidity control).
Precaution for Storage / Transportation
1.
Product performance and soldered connections may deteriorate if the Products are stored in the places where:
[a] the Products are exposed to sea winds or corrosive gases, including Cl2, H2S, NH3, SO2, and NO2
[b] the temperature or humidity exceeds those recommended by ROHM
[c] the Products are exposed to direct sunshine or condensation
[d] the Products are exposed to high Electrostatic
2.
Even under ROHM recommended storage condition, solderability of products out of recommended storage time period
may be degraded. It is strongly recommended to confirm solderability before using Products of which storage time is
exceeding the recommended storage time period.
3.
Store / transport cartons in the correct direction, which is indicated on a carton with a symbol. Otherwise bent leads
may occur due to excessive stress applied when dropping of a carton.
4.
Use Products within the specified time after opening a humidity barrier bag. Baking is required before using Products of
which storage time is exceeding the recommended storage time period.
Precaution for Product Label
A two-dimensional barcode printed on ROHM Products label is for ROHM’s internal use only.
Precaution for Disposition
When disposing Products please dispose them properly using an authorized industry waste company.
Precaution for Foreign Exchange and Foreign Trade act
Since concerned goods might be fallen under listed items of export control prescribed by Foreign exchange and Foreign
trade act, please consult with ROHM in case of export.
Precaution Regarding Intellectual Property Rights
1.
All information and data including but not limited to application example contained in this document is for reference
only. ROHM does not warrant that foregoing information or data will not infringe any intellectual property rights or any
other rights of any third party regarding such information or data.
2.
ROHM shall not have any obligations where the claims, actions or demands arising from the combination of the
Products with other articles such as components, circuits, systems or external equipment (including software).
3.
No license, expressly or implied, is granted hereby under any intellectual property rights or other rights of ROHM or any
third parties with respect to the Products or the information contained in this document. Provided, however, that ROHM
will not assert its intellectual property rights or other rights against you or your customers to the extent necessary to
manufacture or sell products containing the Products, subject to the terms and conditions herein.
Other Precaution
1.
This document may not be reprinted or reproduced, in whole or in part, without prior written consent of ROHM.
2.
The Products may not be disassembled, converted, modified, reproduced or otherwise changed without prior written
consent of ROHM.
3.
In no event shall you use in any way whatsoever the Products and the related technical information contained in the
Products or this document for any military purposes, including but not limited to, the development of mass-destruction
weapons.
4.
The proper names of companies or products described in this document are trademarks or registered trademarks of
ROHM, its affiliated companies or third parties.
Notice-PAA-E
© 2015 ROHM Co., Ltd. All rights reserved.
Rev.003
Datasheet
General Precaution
1. Before you use our Pro ducts, you are requested to care fully read this document and fully understand its contents.
ROHM shall n ot be in an y way responsible or liabl e for fa ilure, malfunction or acci dent arising from the use of a ny
ROHM’s Products against warning, caution or note contained in this document.
2. All information contained in this docume nt is current as of the issuing date and subj ect to change without any prior
notice. Before purchasing or using ROHM’s Products, please confirm the la test information with a ROHM sale s
representative.
3.
The information contained in this doc ument is provi ded on an “as is” basis and ROHM does not warrant that all
information contained in this document is accurate an d/or error-free. ROHM shall not be in an y way responsible or
liable for an y damages, expenses or losses incurred b y you or third parties resulting from inaccur acy or errors of or
concerning such information.
Notice – WE
© 2015 ROHM Co., Ltd. All rights reserved.
Rev.001
Datasheet
BU21028FV-M - Web Page
Part Number
Package
Unit Quantity
Minimum Package Quantity
Packing Type
Constitution Materials List
RoHS
BU21028FV-M
SSOP-B20
2500
2500
Taping
inquiry
Yes