BB BUF08800

BUF08800
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
Programmable Reference Generator
and 400mA VCOM Driver
FEATURES
DESCRIPTION
D 10-BIT RESOLUTION
D 7- OR 8-CHANNEL GAMMA CORRECTION
D INTEGRATED VCOM DRIVER:
D
D
D
D
D
D
D
400mA PEAK CURRENT
DIGITAL GATE VOLTAGE ADJUSTMENT
CIRCUITS
RAIL-TO-RAIL OUTPUT
LOW SUPPLY CURRENT: 1mA/ch
SUPPLY VOLTAGE: 7V to 22V
DIGITAL SUPPLY: 2.0V to 5.5V
INDUSTRY-STANDARD, TWO-WIRE
INTERFACE
HIGH ESD RATING: 4kV HBM
APPLICATIONS
D TFT-LCD REFERENCE DRIVERS
D REFERENCE VOLTAGE GENERATORS
VSD
VS
+IN (VCOM)
BUF08800
Gamma/VCOM Register Bank 2
Gamma/VCOM Register Bank 1
10−Bit
DAC
250kΩ
−IN (VCOM)
10−Bit
DAC
OUT 2
10−Bit
DAC
OUT 3
10−Bit
DAC
OUT 7
10−Bit
DAC
OUT 8
SDA
SCL
VCOM (OUT 1)
Control IF
A0
The BUF08800 reference generator offers eight programmable reference channels that can be used depending on
the application needs. For example, all eight channels can
be used for gamma correction, or some as gamma
references and some to digitally adjust the gate voltages
or VCOM.
All gamma/VCOM channels swing to within 100mV of the
positive or negative supply rail with a 10mA load. All
channels are programmed using a standard two-wire
interface that supports standard operation up to 400kHz
and also high-speed data transfer up to 3.4MHz.
The integrated VCOM driver features up to 400mA peak
current drive. VCOM voltage compensation at different
locations on the LCD panel can be accomplished using the
negative input of the integrated VCOM op amp.
The Gate High and Low voltages can differ because of
changes in panel size or technology. The BUF08800
supports digital adjustment circuits for the gate voltages.
This feature enables the adjustment of gate voltages
through software without changing hardware, thus
reducing development time and risk.
The BUF08800 is manufactured using Texas Instruments’
proprietary, state-of-the-art, high-voltage CMOS process.
This process allows very dense logic as well as high
supply voltage operation of up to 22V.
The BUF08800 is available in a small TSSOP-20
PowerPad package, and is specified from −40°C to
+85°C.
RELATED PRODUCTS
FEATURES
PRODUCT
12-Channel Gamma Correction Buffer
BUF12800
20-Channel Programmable Buffer, 10-Bit, VCOM
BUF20800
16-, 20-Channel Prog. Buffer with Memory
BUF20820
Programmable VCOM Driver
BUF01900
18V Supply, Traditional Gamma Buffers
BUF11704
22V Supply, Traditional Gamma Buffers
BUF11705
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD is a trademark of Texas Instruments. All other trademarks are the property of their respective owners.
Copyright  2007, Texas Instruments Incorporated
! ! www.ti.com
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SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handled with appropriate precautions. Failure to observe
proper handling and installation procedures can cause damage.
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage, VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +24V
Supply Voltage, VSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6V
Supply Input Terminals, SCL, SDA, AO, LD:
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5V to +6V
Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±10mA
Output Short-Circuit(2) . . . . . . . . . . . . . . . . . . . . . . . . . Continuous
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . −40°C to +95°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . −65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +125°C
(1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not supported.
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
(2) Short-circuit to ground.
ORDERING INFORMATION(1)
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR
PACKAGE MARKING
BUF08800
HTSSOP-20
PWP
BUF08800
ORDERING NUMBER
BUF08800AIPWPR
(1) For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI web site
at www.ti.com.
PIN CONFIGURATIONS
Top View
2
HTSSOP
BUF08800
GND
1
20
VCOM (OUT 1)
GND
2
19
VS
+IN (VCOM)
3
18
VS
−IN (VCOM)
4
17
OUT 2
VSD
5
16
OUT 3
SCL
6
15
OUT 4
SDA
7
14
OUT 5
A0
8
13
OUT 6
LD
9
12
OUT 7
GND (digital)
10
11
OUT 8
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ELECTRICAL CHARACTERISTICS
Boldface limits apply over the specified temperature range: TA = −40°C to +85°C.
At TA = +25°C, VS = +18V, VSD = 2.5V, RL = 1.5kΩ to GND, and CL = 200pF, unless otherwise noted.
BUF08800
PARAMETER
CONDITIONS
ANALOG
Gamma Buffer Channels
Reset Value
Buffer 2−4 Output Swing: High
Buffer 2−4 Output Swing: Low
Buffer 5−8 Output Swing: High
Buffer 5−8 Output Swing: Low
Continuous Output Current
Output Accuracy
vs Temperature
Integral Nonlinearity
INL
Differential Nonlinearity
DNL
Load Regulation, 10mA
REG
VCOM Driver/OUT 1
Reset Value
Driver Input Range
Driver Offset
VCOM/OUT 1 Output Swing: High
VCOM/OUT 1 Output Swing: Low
VCOM/OUT 1 Output Swing: High
VCOM/OUT 1 Output Swing: Low
VBIAS Output Impedance
Overall Output Accuracy
vs Temperature
Integral Nonlinearity
INL
Differential Nonlinearity
DNL
Load Regulation, 100mA
REG
Program to Out Delay
tD
Code = 512
Code = 1023, Sourcing 10mA
Code = 0, Sinking 10mA
Code = 1023, Sourcing 10mA
Code = 0, Sinking 10mA
MIN
17.8
17.0
Code 512
Code = 512, IOUT = +5mA to −5mA Step
Code = 00, No Load on Pin 2, IOUT = 0
IOUT = 0mA
Referred to Pin 2, Code = 512
Pin 9, Code = 1023, Sourcing 10mA
Pin 9, Code = 0, Sinking 10mA
Pin 9, Code = 1023, Sourcing 400mA
Pin 9, Code = 0, Sinking 400mA
Pin 2
Pin 20
Code = 512
Pin 20
Pin 20
Pin 20, Code = 512, IOUT = +200mA to −200mA Step
All Channels
DIGITAL
Logic 1 Input Voltage
Logic 0 Input Voltage
Logic 0 Output Voltage
Input Leakage
Clock Frequency
9
17.85
0.7
17.2
0.2
30
±10
±20
0.3
0.3
0.5
17.8
14
1
17.9
0.7
14.6
3.5
250
±20
±25
0.3
0.3
0.5
5
7
IS
VIH
VIL
VOL
MAX
1
0.25
±50
1
2.5
1.5
9
0.7
ANALOG POWER SUPPLY
Operating Range
Total Analog Supply Current
Over Temperature
TYP
Outputs at Reset Values, No Load
7
17.9
±5
1
4
±50
1
2.5
1.5
0.15
±0.01
Standard/Fast Mode
High-Speed Mode
V
V
V
V
V
mA
mV
µV/°C
Bits
Bits
mV/mA
V
V
mV
V
V
V
V
kΩ
mV
µV/°C
Bits
Bits
mV/mA
µs
22
V
15
15
mA
mA
0.3 × VSD
0.4
±10
400
3.4
V
V
V
µA
kHz
MHz
5.5
V
0.7 × VSD
ISINK = 3mA
UNITS
DIGITAL POWER SUPPLY
Operating Range
Digital Supply Current(1)
VSD
ISD
2.0
Outputs at Reset Values, No Load, Two-Wire Bus
Inactive
25
Over Temperature
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance(2)
HTSSOP-20
HTSSOP-20
50
Junction Temperature < +125°C
qJA
qJC
−40
−40
−65
+85
+95
+150
35
20
µA
µA
100
°C
°C
°C
°C/W
°C/W
(1) See typical characteristic curve Digital Supply Current vs Two-Wire Bus Activity.
(2) Thermal pad attached to printed circuit board (PCB), 0lfm airflow, and 76mm × 76mm copper area.
3
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SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = +18V, VSD = 2.5V, RL = 1.5kΩ to GND, and CL = 200pF, unless otherwise noted.
DIGITAL SUPPLY CURRENT vs TEMPERATURE
ANALOG SUPPLY CURRENT vs TEMPERATURE
20
8
7
15
6
IQ (µA)
IQ (mA)
5
4
10
3
5
2
1
0
0
−50
−25
0
25
50
75
100
−50
125
−25
0
25
Temperature (_ C)
50
75
100
125
Temperature (_C)
Figure 1
Figure 2
CHANNEL 2 FULL−SCALE OUTPUT SWING
5V/div
5V/div
CHANNEL 8 FULL−SCALE OUTPUT SWING
1µs/div
1µs/div
Figure 3
Figure 4
DIFFERENTIAL NONLINEARITY ERROR vs INPUT CODE
VCOM CHANNEL FULL−SCALE OUTPUT SWING
1.0
VCOM OUT 1, OUT 2
(5 units shown)
0.8
5V/div
DNL Error (LSB)
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
Limited by Range
of Voltage Buffer
−0.8
−1.0
5µs/div
0
128
256
384
512
640
Input Code
Figure 5
4
Figure 6
768
896
1024
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SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = +18V, VSD = 2.5V, RL = 1.5kΩ to GND, and CL = 200pF, unless otherwise noted.
DIFFERENTIAL NONLINEARITY ERROR vs INPUT CODE
INTEGRAL NONLINEARITY ERROR vs INPUT CODE
1.0
0.8
VCOM OUT 1, OUT 2 (5 units shown)
0.8
0.6
0.4
0.4
INL Error (LSB)
0.6
0.2
0
−0.2
−0.4
−0.6
0.2
0
−0.2
−0.4
−0.6
−0.8
−0.8
Limited by Range of Voltage Buffer
−1.0
0
128
256
384
512
640
768
896
Limited by Range of Voltage Buffer
−1.0
1024
0
128
256
384
Input Code
512
640
768
896
1024
Input Code
Figure 7
Figure 8
INTEGRAL NONLINEARITY ERROR vs INPUT CODE
1.0
OUT 8 (4 units shown)
0.8
0.6
INL Error (LSB)
DNL Error (LSB)
1.0
OUT 8 (4 units shown)
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
Limited by Range of Voltage Buffer
−1.0
0
128
256
384
512
640
768
896
1024
Input Code
Figure 9
5
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SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
1V of the positive supply rail, and to within 250mV of the
negative supply rail. (See the Electrical Characteristics
table for further information.)
APPLICATIONS INFORMATION
The BUF08800 programmable voltage reference allows
fast and easy adjustment of eight programmable reference
outputs, each with 10-bit resolution. It allows very simple,
time-efficient adjustment of the VCOM and gamma
reference voltages. The BUF08800 is programmed
through a high-speed, standard two-wire interface. The
BUF08800 features a double-register structure for each
digital-to-analog converter (DAC) channel to simplify the
implementation of dynamic gamma control (see the
Dynamic Control section). This architecture allows
pre-loading of register data and rapid updating of all
channels simultaneously.
Buffers 2−8 are capable of full-scale change in output
voltage in less than 4µs; see Figure 4.
The BUF08800 uses an analog supply of 7V to 22V and a
digital supply of 2V to 5.5V. The digital supply must be
applied prior to or simultaneously with the analog supply
to avoid excessive current and power consumption;
damage to the device may occur if it is left connected only
to the analog supply for an extended time.
Figure 10 shows the BUF08800 in a typical configuration.
In this configuration, the BUF08800 device address is 74h.
The output of each DAC is immediately updated as soon
as data is received in the corresponding register (LD = 0).
VCOM (OUT 1) and buffers 2−4 are able to swing to within
200mV of the positive supply rail, and to within 1V of the
negative supply rail. Buffers 5−8 are able to swing to within
BUF08800
3.3V
1µ F
(1)
1
GND
V COM (O UT 1)
20
2
GND
VS
19
3
+IN (V COM)
VS
18
4
− IN (V COM)
O UT 2
17
(1)
V COM
10 µ F
100 µ F
(1)
Source
Driver
(1)
5
V SD
O UT 3
16
6
SCL
O UT 4
15
7
SDA
O UT 5
14
8
A0
O UT 6
13
9
LD
O UT 7
12
GND (digital)(2)
O UT 8
11
100nF
(1)
Timing
Controller
(1)
10
(1)
(1)
(1)
(1) RC combination optional
(2) GND and GND (digital) are internally connected and must be at the same voltage potential.
Figure 10. Typical Application Configuration
6
VS
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SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
TWO-WIRE BUS OVERVIEW
DATA RATES
The
BUF08800
communicates
through
an
industry-standard, two-wire interface to receive data in
slave mode. This standard uses a two-wire, open-drain
interface that supports multiple devices on a single bus.
Bus lines are driven to a logic low level only. The device
that initiates the communication is called a master, and the
devices controlled by the master are slaves. The master
generates the serial clock on the clock signal line (SCL),
controls the bus access, and generates the START and
STOP conditions.
The two-wire bus operates in one of three speed modes:
D Standard: allows a clock frequency of up to 100kHz;
D Fast: allows a clock frequency of up to 400kHz; and
D High-speed mode (also called Hs mode): allows a
clock frequency of up to 3.4MHz.
To address a specific device, the master initiates a START
condition by pulling the data signal line (SDA) from a HIGH
to LOW logic level while SCL is HIGH. All slaves on the bus
shift in the slave address byte, with the last bit indicating
whether a read or write operation is intended. During the
ninth clock pulse, the slave being addressed responds to
the master by generating an Acknowledge and pulling
SDA LOW.
Data transfer is then initiated and 8 bits of data are sent
followed by an Acknowledge Bit. During data transfer,
SDA must remain stable while SCL is HIGH. Any change
in SDA while SCL is HIGH will be interpreted as a START
or STOP condition.
Once all data has been transferred, the master generates
a STOP condition indicated by pulling SDA from LOW to
HIGH while SCL is HIGH.
The BUF08800 can act only as a slave device; therefore,
it never drives SCL. SCL is an input only for the BUF08800.
ADDRESSING THE BUF08800
The address of the BUF08800 is 111010x, where x is the
state of the A0 pin. When the A0 pin is LOW, the device
acknowledges on address 74h (1110100). If the A0 pin is
HIGH, the device acknowledges on address 75h
(1110101), as shown in Table 1.
The BUF08800 is fully compatible with all three modes. No
special action is required to use the device in Standard or
Fast modes, but High-speed mode must be activated. To
activate High-speed mode, send a special address byte of
00001xxx, with SCL = 400kHz, following the START
condition; xxx are bits unique to the Hs-capable master,
and can be any value. The BUF08800 responds to the
High-speed mode command regardless of the value of
these last three bits. This byte is called the Hs master
code. (Note that this is different from normal address
bytes—the low bit does not indicate read/write status.) The
BUF08800 does not acknowledge this byte; the
communication protocol prohibits acknowledgment of the
Hs master code. On receiving a master code, the
BUF08800 switches on its Hs mode filters, and
communicates at up to 3.4MHz. Additional high-speed
transfers may be initiated without resending the Hs mode
byte by generating a repeat START without a STOP. The
BUF08800 switches out of Hs mode at the first occurrence
of a STOP condition.
GENERAL CALL RESET AND POWER-UP
The BUF08800 responds to a General Call Reset, which
is an address byte of 00h (0000 0000) followed by a data
byte of 06h (0000 0110). The BUF08800 acknowledges
both bytes. Upon receiving a General Call Reset, the
BUF08800 performs a full internal reset, as though it had
been powered off and then on. It always acknowledges the
General Call address byte of 00h (0000 0000), but does
not acknowledge any General Call data bytes other than
06h (0000 0110).
Other valid addresses are possible through a simple mask
change. Contact your TI representative for information.
The BUF08800 automatically performs a reset upon
power-up. As part of the reset, the BUF08800 is configured
for all outputs to change to mid-value, VS/2.
Table 1. BUF08800 Bus Address Options
The BUF08800 resets all outputs to mid-value (VS/2) when
the device address is sent, followed by a valid DAC
address with bits D7 to D5 set to ‘100’. If these bits are set
to ‘010’, only the DAC being addressed in this most
significant byte and the following least significant byte will
be reset.
BUF08800 ADDRESS
ADDRESS
A0 pin is LOW
(device will not acknowledge on address 74h)
111 0100
A0 pin is HIGH
(device will acknowledge on address 74h)
111 0101
Table 2. Quick-Reference Table of Commands
COMMAND
CODE
General Call Reset
Address byte of 00h (0000 0000) followed by a data byte of 06h (0000 0110).
High-Speed Mode
00001xxx, with SCL ≤ 400kHz; where xxx are bits unique to the Hs-capable master.
This byte is called the Hs master code.
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OUTPUT VOLTAGE
4.
Send two bytes of data for the specified DAC. Begin
by sending the most significant byte first (bits
D15−D8, of which only bits D9 and D8 are used),
followed by the least significant byte (bits D7−D0).
The DAC register is updated after receiving the
second byte.
5.
Send a STOP condition on the bus.
Buffer output values are determined by the supply voltage
and the decimal value of the binary input code used to
program that buffer. The value is calculated using
Equation 1:
VOUT +
ǒ
VS
1024
Ǔ
Decimal Value of Code
(1)
The BUF08800 outputs 2−8 are capable of a full-scale
voltage output change in typically 4µs—no intermediate
steps are required. Output swing is limited to the voltages
specified in the Electrical Characteristics table. VCOM
(OUT 1) through OUT 4 can swing from 1V to VS − 0.2V;
OUT 5 through OUT 8 can swing between 0.25V and VS
− 1V.
READ/WRITE OPERATIONS
The BUF08800 is able to read from a single DAC or
multiple DACs, or write to the register of a single DAC, or
multiple DACs in a single communication transaction. See
the timing diagrams; Figure 11 through Figure 14. DAC
addresses begin with 0000, which correspond to VCOM
(OUT 1), through 0111, which correspond to DAC_8; this
address archetecture is shown in Table 3. Write
commands are performed by setting the read/write bit
LOW. Setting the read/write bit HIGH performs a read
transaction.
Table 3. Quick-Reference Table of DAC
Addresses
DAC
ADDRESS
VCOM OUT 1
0000 0000
DAC 2
0000 0001
DAC 3
0000 0010
DAC 4
0000 0011
DAC 5
0000 0100
DAC 6
0000 0101
DAC 7
0000 0110
DAC 8
0000 0111
The BUF08800 acknowledges each data byte. If the
master terminates communication early by sending a
STOP or START condition on the bus, the specified
register will not be updated. Updating the DAC register is
not the same as updating the DAC output voltage. See the
Output Latch section.
The process of updating multiple registers begins the
same as when updating a single register. However,
instead of sending a STOP condition after writing the
addressed register, the master continues to send data for
the next register. The BUF08800 automatically and
sequentially steps through subsequent registers as
additional data are sent. The process continues until all
desired registers have been updated or a STOP condition
is sent.
To write to multiple registers:
1.
Send a START condition on the bus.
2.
Send the device address and read/write bit = LOW.
The BUF08800 acknowledges this byte.
3.
Send either the VCOM (OUT 1) address byte to start at
the first DAC (VCOM OUT 1) or send the address of
whichever DAC is the first to be updated. The
BUF08800 begins with this DAC and steps through
subsequent DACs in sequential order.
4.
Send the bytes of data. The first two bytes are for the
DAC addressed in step 3. Its register is automatically
updated after receiving the second byte. The next two
bytes are for the following DAC. The DAC register is
updated after receiving the fourth byte. The last two
bytes are for DAC_8. The DAC register is updated
after receiving the 24th byte. For each DAC, begin by
sending the most significant byte (bits D15−D8, of
which only bits D9 and D8 have meaning), followed by
the least significant byte (bits D7−D0).
Send a STOP condition on the bus.
Writing
To write to a single DAC register:
1.
Send a START condition on the bus.
2.
Send the device address and read/write bit = LOW.
The BUF08800 acknowledges this byte.
5.
3.
Send a DAC address byte. Bits D7−D3 are unused
and must be set to 0. Bits D2−D0 are the DAC
address. Only DAC addresses 0000 to 0111 are valid
and will be acknowledged.
The BUF08800 acknowledges each byte. To terminate
communication, send a STOP or START condition on the
bus. Only DACs that have received both bytes will be
updated.
8
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Reading
To read multiple DAC registers:
To read the register of one DAC:
1.
Send a START condition on the bus.
1.
Send a START condition on the bus.
2.
2.
Send the device address and read/write bit = LOW.
The BUF08800 acknowledges this byte.
Send the device address and read/write bit = LOW.
The BUF08800 acknowledges this byte.
3.
3.
Send a DAC address byte. Bits D7−D3 have no
meaning and must be ‘0’; bits D2−D0 are the DAC
address. Only DAC addresses 0000 to 0111 are valid
and will be acknowledged.
Send either the VCOM DAC (VCOM OUT 1) address
byte to start at the first DAC or send the address byte
for whichever DAC is the first in the sequence of
DACs to be read. The BUF08800 begins with this
DAC and steps through subsequent DACs in
sequential order.
4.
Send the device address and read/write bit = HIGH.
4.
Send a START or STOP/START condition on the bus.
5.
Send correct device address and read/write bit =
HIGH. The BUF08800 acknowledges this byte.
5.
6.
Receive two bytes of data. They are for the specified
DAC. The first received byte is the most significant
byte (bits D15−D8, of which only bits D9 and D8 have
meaning); the next is the least significant byte (bits
D7−D0).
Receive bytes of data. The first two bytes are for the
specified DAC. The first received byte is the most
significant byte (bits D15−D8, of which only bits D9
and D8 have meaning). The next byte is the least
significant byte (bits D7−D0).
6.
Acknowledge after receiving each byte.
7.
Acknowledge after receiving each byte.
7.
8.
Send a STOP condition on the bus.
When all desired DACs have been read, send a
STOP or START condition on the bus.
Communication may be terminated by sending a
premature STOP or START condition on the bus, or by not
sending the acknowledge.
Communication may be terminated by sending a
premature STOP or START condition on the bus, or by not
sending the acknowledge.
9
10
D0
D0
Ackn
Ackn
Figure 11. Write Single DAC Register
No Ackn
No Ackn
Stop
Ackn
D1
D1
D2
D2
D0
D0
D1
D1
D2
D2
D3
D3
D4
D4
D5
D5
D3
D6
D6
D4
D4
DAC LSbyte
D3
DAC LSbyte
The whole DAC Register D9 −D0
is updated in this moment.
Stop
D7
D7
D5
D5
Ackn
Ackn
Ackn
D6
D6
D8
D8
Ackn
Ackn
D8
D8
D9
D9
D10
D10
D9
D9
D10
D10
D11
D11
D12
D12
D13
D13
D12
D12
D13
D13
D14
D14
D15
D15
Ackn
Ackn
Ackn
P0
P0
P1
P1
P2
P2
D14
D14
D15 Ackn
D15 Ackn
R
R
Ackn Read
A0
A0
A1
A1
A2
A2
A3
A3
A4
A4
A5
A5
Device Address
A6
A6
Start
Ackn
Ackn
Ackn
D3
D3
D5
D5
D6
D6
D7
D7
Ackn
Ackn
A0
A0
A1
A1
P0
P0
P1
P1
P2
P2
D3
D3
D4
D4
D5
D5
A2
A2
A3
A3
A4
A4
Device Address
A5
A5
A6
A6
Start
Write single DAC register. P3 −P0 specify the DAC address.
D6
D6
D7
D7
Ackn
Ackn
W
W
A0
A0
A1
A1
A2
A2
A3
A3
A4
A4
Device Address
A5
A5
A6
A6
Start
Read Operation Read single DAC register. P3 −P0 specify DAC address.
W
W
Write
DAC address pointer. D7 −D3 have no meaning. Ackn Write
D4
D4
Ackn
Write Operation
DAC address pointer. D7 −D3 have no meaning.
If D15 = 0, the DACs are updated on the Latch pin.
If D15 = 1, all DACs are updated when the current DAC register is updated.
D11
D11
DAC MSbyte. D14 −D10 have no meaning.
DAC MSbyte. D15 −D10 have no meaning.
D7
D7
Ackn
Device_Out
SDA_In
SCL
Device_Out
SDA_In
SCL
"#$%%$$
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
www.ti.com
Figure 12. Read Single DAC Register
Figure 13. Write Multiple DAC Registers
A0
A6
A6
SDA_In
Device_Out
SCL
A1
A0
W
Ackn
D7
D7
A5
A5
A4
A4
A3
A3
Device Address
A2
A2
A1
A1
A0
A0
W
W
Write
Ackn
Ackn
D6
D6
D5
D5
D4
D4
D3
D3
P2
P2
P1
P1
D7
D7
D6
D6
D5
D5
D4
D4
D3
D3
P2
P2
P1
P1
Start DAC address pointer. D7 −D3 have no meaning.
Ackn
A2
Ackn
Read operation
A3
W
Start
A4
A3
Read multiple DAC registers. P3 −P0 specify start DAC address.
A5
A4
P0
D14
D14
D12
D12
D11
D11
D10
D10
D13
D13
D12
D12
D11
D11
D10
D10
D9
D9
D15
D15
A6
A6
A5
A5
A4
A4
A3
A3
Device Address
A2
A2
D14
D14
D13
D13
D12
D12
D11
D11
D10
D10
D9
D9
DAC(11) MSbyte. D15 −D10 have no meaning.
Start
…
Ackn
Ackn
D13
D13
DAC(11) MSbyte. D14 −D10 have no meaning.
…
…
…
P0
P0
Ackn
D15
…
D14
D14
D9
D9
D8
D8
Ackn
Ackn
D7
D7
D8
D8
Ackn
Ackn
Ackn
D7
D7
A1
A1
D8
D8
Ackn
Ackn
Ackn
A0
A0
R
R
Read
D7
D7
Ackn
Ackn
Ackn
D6
D6
D6
D6
If D15 = 0, the DACs are updated on the Latch pin.
If D15 = 1, all DACs are updated when the current DAC register is updated.
D15
D15
If D15 = 0, the DACs are updated on the Latch pin.
If D15 = 1, all DACs are updated when the current DAC register is updated.
D15
Ackn
…
…
…
P0
Ackn
D6
D4
D4
D4
D4
D3
D3
D3
DAC(11) LSbyte
D5
D4
D2
D1
D0
D1
D0
D15
D15
D5
D5
D13
D13
D12
D12
D4
D4
D3
D3
DAC(11) LSbyte
D14
D14
Ackn
D1
D1
D0
D0
Ackn
Ackn
Ackn
Stop
The whole DAC Register D9 −D0
is updated in this moment.
D2
Ackn
D2
D2
D11
D11
D1
D1
D10
D10
D0
D0
Ackn
D9
D9
D8
D8
Stop
The whole DAC Register D9 −D0
is updated in this moment.
D2
D2
D2
D3
D3
DAC(pointer) MSbyte. D15 −D10 have no meaning.
D5
D5
D6
D5
…
…
…
…
…
A6
A1
…
Device_Out
A2
Ackn
…
A5
DAC(pointer) LSbyte
A6
Ackn
SDA_In
DAC(pointer) MSbyte. D14 −D10 have no meaning.
…
Ackn
DAC(pointer+1) MSbyte.
D14 −D10 have no meaning.
SCL
Start DAC address pointer. D7 −D3 have no meaning.
Ackn
Write
Start
Device Address
Write Operation
Write multiple DAC registers. P3 −P0 specify start DAC address.
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
Figure 14. Read Multiple DAC Registers
11
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
OUTPUT LATCH
Because the BUF08800 features a double-buffered
register structure, updating a DAC register is not the same
as updating the DAC output voltage. There are three
methods for latching transferred data from the storage
registers into the DACs to update the DAC output voltage.
Method 1 requires externally setting the latch pin (LD) =
LOW, which updates each DAC output voltage whenever
its corresponding register is updated.
Method 2 externally sets LD = HIGH to allow all DAC
output voltages to retain their values during data transfer
and until LD = LOW, which simultaneously updates the
output voltages of all DACs to the new register values.
Method 3 uses software control. LD is maintained HIGH,
and all DACs are updated when the master writes a ‘1’ in
bit 15 of any DAC register. The update occurs after
receiving the 16-bit data for the currently-written register.
Use methods 2 and 3 to transfer a future data set into the
first bank of registers in advance to prepare for a very fast
update of DAC output voltages.
The General Call Reset and the power-up reset update the
DACs regardless of the state of the latch pin (LD).
REPLACEMENT OF TRADITIONAL GAMMA
BUFFER
Traditional gamma buffers rely on a resistor string (often
using expensive 0.1% resistors) to set the gamma
voltages. During development, the optimization of these
gamma voltages can be time-consuming. Programming
these gamma voltages with the BUF08800 can
significantly reduce the time required for gamma voltage
optimization. The final gamma values can be written into
the internal OTP memory to replace a traditional gamma
buffer solution. Figure 16a shows the traditional resistor
string; Figure 16b shows the more efficient alternative
method using the BUF08800.
The BUF08800 uses the most advanced high-voltage
CMOS process available today, allowing it to be
competitive with traditional gamma buffers.
Programmability offers the following advantages:
D
D
Shortens development time significantly.
D
D
Eliminates manufacturing variance between panels.
D
12
Increases reliability by eliminating more than 18
external components.
Allows a single panel to be built for multiple
customers, with loading of customer-dependent
gamma curves during final production. This method
significantly lowers inventory cost and risk, and
simplifies inventory management.
Allows demonstration of various gamma curves to
LCD monitor makers by simply uploading a different
set of gamma values.
D
Allows simple adjustment of gamma curves during
production to accommodate changes in the panel
manufacturing process or end-customer requirements.
D
Decreases cost and space.
VCOM ADJUSTMENT
The output of the VCOM digital-to-analog converter (DAC)
is internally connected to the input of the VCOM buffer. As
a result of the high 10-bit resolution, the VCOM voltage can
directly be adjusted without the need for external circuitry.
The integrated VCOM driver can deliver up to 400mA of
peak current. In addition, the negative input is brought out
as a separate pin on the package to facilitate VCOM
compensation or equalization of the VCOM voltage across
the panel (see Figure 17).
Traditional VCOM adjustment uses a mechanical
potentiometer and a voltage divider for adjustment, as
shown in Figure 15. The programmable VCOM channel
integrated in the BUF08800 is also able to use an external
voltage divider connected to +IN. It can be used to set the
initial VCOM voltage as well as the adjustment range (see
Figure 17). Using this method, even at power-on the initial
VCOM setting is close to the optimized VCOM value, without
any programming. The external voltage divider also limits
the adjustment range that typically leads to a smaller
number of adjustment steps. In addition, the VCOM output
voltage is limited only to the adjustment range, thereby
protecting the panel from undesirable VCOM voltages.
AVDD
RA
RB
VCOM
RC
Figure 15. Traditional VCOM Adjustment. External
voltage divider sets initial VCOM voltage as well as
adjustment range.
The 10-bit DAC acts as a voltage source with a nominal
250kΩ output impedance; see Figure 17. For example, at
code 000h, the lowest VCOM voltage is achieved because
the 250kΩ impedance is now in parallel with R2, which
lowers the impedance of the lower side of the voltage
divider. Consequently, code 3FFh results in the highest
adjustable VCOM voltage.
However, an external voltage divider is not required for
correct function of the VCOM channel integrated in the
BUF08800. Once the desired output level (that is,
minimum flicker) is obtained, the corresponding code can
be stored in the external EEPROM memory.
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
a) Traditional Solution
b) BUF08800 Solution
BUFxx704
BUF08800
VCOM OUT 1
VCOM
OUT 2
Timing
Controller
OUT 3
PC
Register
SDA
SCL
Gamma
References
OUT 7
EEPROM
OUT 8
SDA
Control Interface
SCL
LCD Panel Electronics
Figure 16. Replacement of the Traditional Gamma Buffer
Analog
7V to 18V
R1
Code 3FF
10−Bit
DAC
250kΩ
BUF08800
+IN (VCOM)
VCOM/OUT 2
Code 00
R2
−IN (VCOM)
Figure 17. Simplified Block Diagram for VCOM Adjustment Using the BUF08800
13
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
DIGITAL GATE-VOLTAGE (VGH, VGL)
ADJUSTMENT
Different panel sizes and manufacturing technology often
require different gate-high (VGH) and gate-low (VGL)
voltages. Optimizing the gate-high and -low voltages for
best panel performance can be time consuming. Using
channels 7 and 8, which are capable of swinging close to
GND, allows a wide range of programmable adjustment of
both VGL and VGH. This procedure of optimizing VGH and
VGL is greatly simplified and the LCD power-supply
solution can readily be used in other panels without
modification to the hardware.
TYPICAL APPLICATIONS FOR BUF08800
1.
OUT 3 would then form the four upper gamma
references and OUT 4 through OUT 8 would be used
for the four lower gamma references.
2.
Five-channel gamma reference, two-channel gate
voltage adjust, one-channel VCOM. For applications
that can accept a total of five gamma references, the
BUF08800 can be used to digitally adjust the gate
voltages. Two channels would be used to adjust VGH
and VGL. In this case, the suggested use of channels
would be to use OUT 2 through OUT 6 for generating
the gamma references and OUT 7 and OUT 8 for
generating the VGH and VGL references. OUT 1 would
be used as the VCOM channel.
3.
Six-channel gamma, one VCOM channel. For
applications requiring one VCOM channel and an even
number of gamma channels, the BUF08800 would
still be a very cost-competitive solution. Channels 2
through 7 would be used to generate the gamma
references.
All eight channels are used for gamma correction.
The VCOM channel swings very close to VS. It can
therefore be used to generate the highest gamma
voltage. VCOM (OUT 1) together with OUT 2 and
36V Unregulated
VGATE High
R
VSD
Programmable
VGATE High
VGH = VDIODE + OUT 8 − VBE (NPN)
VS
VGATE Adj Register 2
VGATE Adj Register 1
D
… …
Control IF
SCL
OUT 8
10−Bit
DAC
OUT 7
D
VGH = VDIODE + OUT 7 − VBE (NPN)
10−Bit
DAC
…
SDA
10−Bit
DAC
Programmable
VGATE Low
R
BUF08800
Unregulated
VGATE Low
A0
Figure 18. Using the BUF08800 to Digitally Adjust the VGH Voltage
14
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
GENERAL POWERPAD DESIGN
CONSIDERATIONS
The BUF08800 is available in a thermally-enhanced
PowerPAD package. This package is constructed using a
downset leadframe upon which the die is mounted; see
Figure 19(a) and Figure 19(b). This arrangement results in
the lead frame being exposed as a thermal pad on the
underside of the package; see Figure 19(c). This thermal
pad has direct thermal contact with the die; thus, excellent
thermal performance is achieved by providing a good
thermal path away from the thermal pad.
The PowerPAD package allows for both assembly and
thermal management in one manufacturing operation.
During the surface-mount solder operation (when the
leads are being soldered), the thermal pad must be
soldered to a copper area underneath the package.
Through the use of thermal paths within this copper area,
heat can be conducted away from the package into either
a ground plane or other heat-dissipating device. Soldering
the PowerPAD to the printed circuit board (PCB) is always
required, even with applications that have low power
dissipation. This process provides the necessary thermal
and mechanical connection between the lead frame die
pad and the PCB.
The PowerPAD must be connected to the most negative
supply voltage on the device, GNDA and GNDD.
1.
Prepare the PCB with a top-side etch pattern. There
should be etching for the leads as well as for the
thermal pad.
2.
Place recommended holes in the area of the thermal
pad. Ideal thermal land size and thermal via patterns
(2×4) for the HTSSOP-20 DAP package can be seen
in the technical brief, PowerPAD ThermallyEnhanced Package (SLMA002), available for download at www.ti.com. These holes should be 13 mils in
diameter. Keep them small, so that solder wicking
through the holes is not a problem during reflow.
3.
Additional vias may be placed anywhere along the
thermal plane outside of the thermal pad area. The
vias help dissipate the heat generated by the
BUF08800 IC. The additional vias may be larger than
the 13-mil diameter vias directly under the thermal
pad. They can be larger because they are not in the
thermal pad area to be soldered; thus, wicking is not
a problem.
4.
Connect all holes to the internal plane that is at the
same voltage potential as the GND pins.
5.
When connecting these holes to the internal plane, do
not use the typical web or spoke via connection
methodology. Web connections have a high thermal
resistance connection that is useful for slowing the
heat transfer during soldering operations, making the
soldering of vias that have plane connections easier.
In this application, however, low thermal resistance is
desired for the most efficient heat transfer. Therefore,
the holes under the BUF08800 PowerPAD package
should make their connection to the internal plane
with a complete connection around the entire
circumference of the plated-through hole.
6.
The top-side solder mask should leave the terminals
of the package and the thermal pad area with its ten
holes exposed. The bottom-side solder mask should
cover the holes of the thermal pad area. This masking
prevents solder from being pulled away from the
thermal pad area during the reflow process.
7.
Apply solder paste to the exposed thermal pad area
and all of the IC terminals.
8.
With these preparatory steps in place, the BUF08800
IC is simply placed in position and run through the
solder reflow operation as any standard
surface-mount component. This preparation results in
a properly installed part.
15
"#$%%$$
www.ti.com
SBOS380A − FEBRUARY 2007 − REVISED MAY 2007
DIE
Side View (a)
DIE
End View (b)
Exposed
Thermal
Pad
Bottom View (c)
Figure 19. Views of Thermally-Enhanced DCP Package
For a given qJA, the maximum power dissipation is shown
in Figure 20, and is calculated by Equation 3:
ǒT
MAX
* TA
q JA
Ǔ
(2)
Where:
PD = maximum power dissipation (W)
TMAX = absolute maximum junction temperature (+125°C)
TA = ambient air temperature (°C)
qJA = qJC + qCA
qJC = thermal coefficient from junction-to-case (°C/W)
qCA = thermal coefficient from case-to-ambient air (°C/W)
Maximum Power Dissipation (W)
PD +
6
5
4
3
2
1
0
−40
−20
0
20
40
60
80
100
TA, Free−Air Temperature (_ C)
Figure 20. Maximum Power Dissipation vs
Free-Air Temperature
(with PowerPAD soldered down)
16
PACKAGE OPTION ADDENDUM
www.ti.com
25-Apr-2007
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
BUF08800AIPWPR
ACTIVE
HTSSOP
PWP
20
2000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
BUF08800AIPWPRG4
ACTIVE
HTSSOP
PWP
20
2000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
21-May-2007
TAPE AND REEL INFORMATION
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
Device
BUF08800AIPWPR
21-May-2007
Package Pins
PWP
20
Site
Reel
Diameter
(mm)
Reel
Width
(mm)
A0 (mm)
B0 (mm)
K0 (mm)
P1
(mm)
TAI
330
16
6.95
7.1
1.6
8
TAPE AND REEL BOX INFORMATION
Device
Package
Pins
Site
Length (mm)
Width (mm)
Height (mm)
BUF08800AIPWPR
PWP
20
TAI
346.0
346.0
33.0
Pack Materials-Page 2
W
Pin1
(mm) Quadrant
16
Q1
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