TLC540IJ [TI]
IC IC,DATA ACQ SYSTEM,11-CHANNEL,8-BIT,DIP,20PIN,CERAMIC, Analog IC:Other;
| 型号： | TLC540IJ |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | IC IC,DATA ACQ SYSTEM,11-CHANNEL,8-BIT,DIP,20PIN,CERAMIC, Analog IC:Other 转换器 输入元件 |
| 文件： | 总11页 (文件大小：166K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
DW OR N PACKAGE
(TOP VIEW)
8-Bit Resolution A/D Converter
Microprocessor Peripheral or Stand-Alone
Operation
INPUT A0
INPUT A1
INPUT A2
INPUT A3
INPUT A4
INPUT A5
INPUT A6
INPUT A7
INPUT A8
GND
V
CC
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
On-Chip 12-Channel Analog Multiplexer
Built-in Self-Test Mode
SYSTEM CLOCK
I/O CLOCK
ADDRESS INPUT
DATA OUT
CS
REF+
REF–
INPUT A10
INPUT A9
Software-Controllable Sample and Hold
Total Unadjusted Error . . . ±0.5 LSB Max
TLC541 is Direct Replacement for Motorola
MC145040 and National Semiconductor
ADC0811. TLC540 is Capable of Higher
Speed
Pinout and Control Signals Compatible
with TLC1540 Family of 10-Bit A/D
Converters
FN PACKAGE
(TOP VIEW)
CMOS Technology
PARAMETER
TLC540
TLC541
Channel Acquisition Sample Time
Conversion Time (Max)
Samples per Second (Max)
Power Dissipation (Max)
2 µs
9 µs
75 x 10
12.5 mW
3.6 µs
17 µs
40 x 10
12.5 mW
3
3
description
3
2
1
20 19
18
I/O CLOCK
INPUT A3
4
5
6
7
8
The TLC540 and TLC541 are CMOS A/D
converters built around an 8-bit switched-
capacitor
converters. They are designed for serial interface
to a microprocessor or peripheral via a 3-state
output with up to four control inputs, including
independent SYSTEM CLOCK, I/O CLOCK, chip
select (CS), and ADDRESS INPUT. A 4-MHz
system clock for the TLC540 and a 2.1-MHz
system clock for the TLC541 with a design that
ADDRESS INPUT
DATA OUT
CS
INPUT A4
INPUT A5
INPUT A6
INPUT A7
17
16
15
14
successive-approximation
A/D
REF+
9 10 11 12 13
includes simultaneous read/write operation allow high-speed data transfers and sample rates of up to
75,180samples per second for the TLC540 and 40,000 samples per second for the TLC541. In addition to the
high-speed converter and versatile control logic, there is an on-chip 12-channel analog multiplexer that can be
used to sample any one of 11 inputs or an internal self-test voltage, and a sample-and-hold that can operate
automatically or under microprocessor control. Detailed information on interfacing to most popular
microprocessors is readily available from the factory.
AVAILABLE OPTIONS
PACKAGE
T
A
SO PLASTIC DIP
(DW)
PLASTIC DIP
(N)
CHIP CARRIER
(FN)
—
TLC540IN
TLC541IN
TLC540IFN
TLC541IFN
–40°C to 85°C
–55°C to 125°C
TLC541IDW
—
TLC541MN
—
Copyright 1995, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
The converters incorporated in the TLC540 and TLC541 feature differential high-impedance reference inputs
that facilitate ratiometric conversion, scaling, and analog circuitry isolation from logic and supply noises. A
switched-capacitor design allows low-error (±0.5 LSB) conversion in 9 µs for the TLC540 and 17 µs for the
TLC541 over the full operating temperature range.
The TLC540I and TLC541I are characterized for operation from –40°C to 85°C.The TLC541M is characterized
for operation from –55°C to 125°C.
functional block diagram
REF+
14
REF–
13
8-Bit
Analog-to-Digital
Converter
1
2
3
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
Sample
and
Hold
(Switched-Capacitors)
4
5
6
7
8
9
11
12
12-Channel
Analog
Multiplexer
8
Analog
Inputs
Output
Data
Register
8-to-1 Data
Selector
and Driver
8
16
DATA
OUT
Input
Address
Register
4
4
4
Self-Test
Reference
Control Logic
and I/O
Counters
Input
Multiplexer
2
17
ADDRESS
INPUT
18
I/O
CLOCK
15
19
CS
SYSTEM
CLOCK
typical equivalent inputs
INPUT CIRCUIT IMPEDANCE DURING SAMPLING MODE
INPUT CIRCUIT IMPEDANCE DURING HOLD MODE
1 kΩ TYP
INPUT
A0–A10
5 MΩ TYP
INPUT
A0–A10
C = 60 pF TYP
i
(equivalent input
capacitance)
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
operating sequence
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
I/O
CLOCK
Don’t
Care
Access
Cycle B
(see Note C)
Sample
Cycle B
Access
Cycle C
t
Sample
Cycle C
conv
See Note A
CS
t
wH(CS)
Don’t Care
MSB
LSB
MSB
LSB
ADDRESS
INPUT
Don’t Care
B3 B2 B1 B0
C3 C2 C1 C0
Hi-Z
Hi-Z State
A7
State
DATA
OUT
A7
A6 A5 A4 A3 A2 A1 A0
B7 B6 B5 B4 B3 B2 B1 B0
Conversion Data B
B7
Previous Conversion Data A
LSB
MSB
MSB
MSB
LSB
MSB
(See Note B)
NOTES: A. The conversion cycle, which requires 36 system clock periods, is initiated on the 8th falling edge of I/O CLOCK after CS goes low
for the channel whose address exists in memory at that time. If CS is kept low during conversion, I/O CLOCK must remain low
for at least 36 system clock cycles to allow conversion to be completed.
B. The most significant bit (MSB) will automatically be placed on the DATA OUT bus after CS is brought low. The remaining seven
bits (A6–A0) will be clocked out on the first seven I/O CLOCK falling edges.
C. To minimize errors caused by noise at CS, the internal circuitry waits for three system clock cycles (or less) after a chip select
falling edge is detected before responding to control input signals. Therefore, no attempt should be made to clock-in address data
until the minimum chip-select setup time has elapsed.
†
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
(see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 V
CC
Input voltage range, V (any input) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.3 V to V
Output voltage range, V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.3 V to V
+0.3 V
+0.3 V
I
CC
CC
O
Peak input current range (any input) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±10 mA
Peak total input current (all inputs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±30 mA
Operating free-air temperature range, T : TLC540I, TLC541I . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C
A
Storage temperature range, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
stg
Case temperature for 10 seconds: FN package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds: DW or N package . . . . . . . . . . . . . . . 260°C
†
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltage values are with respect to digital ground with REF– and GND wired together (unless otherwise noted).
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
recommended operating conditions
TLC540
NOM
5
TLC541
UNIT
MIN
4.75
2.5
–0.1
1
MAX
5.5
MIN NOM
MAX
5.5
Supply voltage, V
4.75
2.5
– 0.1
1
5
V
V
V
V
V
V
V
CC
Positive reference voltage, V
(see Note 2)
(see Note 2)
– V (see Note 2)
V
CC
0
V
V
+0.1
2.5
V
V
V
V
+0.1
2.5
ref+
CC
CC
0
CC
Negative reference voltage, V
ref–
Differential reference voltage, V
V
CC
+0.2
+0.2
ref+
ref–
CC
CC
CC
Analog input voltage (see Note 2)
High-level control input voltage, V
0
V
CC
0
V
CC
2
2
IH
Low-level control input voltage, V
0.8
0.8
IL
Setup time, address bits at data input before I/O CLOCK↑,
200
0
400
0
ns
t
su(A)
Hold time, address bits after I/O CLOCK↑, t
ns
h(A)
System
clock
cycles
Setup time, CS low before clocking in first address bit, t
(see Note 3)
su(CS)
3
3
System
clock
cycles
CS high during conversion, t
wH(CS)
36
0
36
0
I/O CLOCK frequency, f
clock(I/O)
2.048
4
1.1
2.1
MHz
MHz
MHz
MHz
ns
Pulse duration, SYSTEM CLOCK frequency, f
f
f
clock(SYS)
clock(I/O)
110
clock(I/O)
210
Pulse duration, SYSTEM CLOCK high, t
Pulse duration, SYSTEM CLOCK low, t
wH(SYS)
100
200
200
190
404
404
wL(SYS)
Pulse duration, I/O clock high, t
wH(I/O)
Pulse duration, I/O clock low, t
ns
wL(I/O)
f
≤ 1048 kHz
30
20
30
20
clock(SYS)
System
I/O
f
f
f
> 1048 kHz
Clock transition time
(see Note 4)
clock(SYS)
ns
≤ 525 kHz
100
40
100
40
clock(I/O)
clock(I/O)
> 525 kHz
Operating free-air temperature, T
TLC540I, TLC541I
–40
85
–40
85
°C
A
NOTES: 2. Analog input voltages greater than that applied to REF + convert as all “1”s (11111111), while input voltages less than that applied
to REF– convert as all “0”s (00000000). For proper operation, REF+ voltage must be at least 1 V higher than REF– voltage. Also,
the total unadjusted error may increase as this differential reference voltage falls below 4.75 V.
3. To minimize errors caused by noise at CS, the internal circuitry waits for three SYSTEM CLOCK cycles (or less) after a chip select
falling edge is detected before responding to control input signals. Therefore, no attempt should be made to clock in an address until
the minimum chip select setup time has elapsed.
4. This is the time required for the clock input signal to fall from V min to V max or to rise from V max to V min. In the vicinity
IH
IL
IL
IH
of normal room temperature, the devices function with input clock transition time as slow as 2 µs for remote data acquisition
applications where the sensor and the A/D converter are placed several feet away from the controlling microprocessor.
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
electrical characteristics over recommended operating temperature range, V
= V
= 4.75 V to
CC
ref+
5.5 V, f
= 2.048 MHz for TLC540 or f
= 1.1 MHz for TLC541 (unless otherwise noted)
clock(I/O)
clock(I/O)
†
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V
V
V
High-level output voltage, DATA OUT
V
V
V
V
= 4.75 V,
= 4.75 V,
I
= 360 µA
2.4
OH
CC
OH
Low-level output voltage
I
= 1.6 mA
0.4
10
V
OL
CC
OL
= V
CC
= 0,
,
CS at V
O
O
CC
CC
I
Off-state (high-impedance state) output current
µA
OZ
CS at V
–10
2.5
I
I
I
High-level input current
Low-level input current
Operating supply current
V =V
0.005
–0.005
1.2
µA
µA
IH
I
CC
V = 0
–2.5
2.5
IL
I
CS at 0 V
mA
CC
Selected channel at V
Unselected channel at 0 V
,
CC
0.4
1
Selected channel leakage current
Supply and reference current
µA
Selected channel at 0 V,
–0.4
–1
Unselected channel at V
CC
CS at 0 V
I
+ I
V
ref+
= V
,
CC
1.3
7
3
55
15
mA
pF
CC ref
Analog inputs
Input capacitance
C
i
Control inputs
5
†
All typical values are at T = 25°C.
A
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
operating characteristics over recommended operating free-air temperature range,
V
= V
– 4.75 V to 5.5 V, f
= 2.048 MHz for TLC540 or 1.1 MHz for TLC541,
CC
ref+
clock(I/O)
f
= 4 MHz for TLC540 or 2.1 MHz for TLC541
clock(SYS)
TLC540
MIN MAX
TLC541
MIN MAX
PARAMETER
TEST CONDITIONS
UNIT
E
E
E
Linearity error
See Note 5
±0.5
±0.5
±0.5
±0.5
±0.5
±0.5
±0.5
±0.5
LSB
LSB
LSB
LSB
L
Zero–scale error
Full-scale error
See Notes 2 and 6
See Notes 2 and 6
See Note 7
ZS
FS
Total unadjusted error
Input A11 address = 1011,
(see Note 8)
01111101 10000011 01111101 10000011
Self-test output code
(125)
(131)
(125)
(131)
t
t
Conversion time
See Operating Sequence
See Operating Sequence
9
17
µs
µs
conv
Total access and conversion time
13.3
25
I/O
clock
cylces
Channel acquisition time (sample cycle)
See Operating Sequence
4
4
a
Time output data remains valid after
I/O CLOCK↓
t
t
10
10
ns
ns
v
Delay time, I/O CLOCK↓ to data output
valid
300
400
d
See Parameter
Measurement
Information
t
t
t
t
Output enable time
Output disable time
Data bus rise time
Data bus fall time
150
150
300
300
150
150
300
300
ns
ns
ns
ns
en
dis
r(bus)
f(bus)
NOTES: 2. Analog input voltages greater than that applied to REF+ convert to all “1”s (11111111) while input voltages less than that applied to
REF– convert to all “0”s (00000000). For proper operation, REF+ voltage must be at least 1 V higher than REF– voltage. Also, the
total unadjusted error may increase as this differential reference voltage falls below 4.75 V.
5. Linearity error is the maximum deviation from the best straight line through the A/D transfer characteristics.
6. Zero-scale error is the difference between 00000000 and the converted output for zero input voltage; full-scale error is the difference
between 11111111 and the converted output for full-scale input voltage.
7. Total unadjusted error is the sum of linearity, zero-scale, and full-scale errors.
8. Both the input address and the output codes are expressed in positive logic.
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
PARAMETER MEASUREMENT INFORMATION
V
CC
1.4 V
3 kΩ
3 kΩ
Test
Point
Output
Under Test
Test
Point
Output
Under Test
Test
Point
Output
Under Test
C
C
L
C
L
3 kΩ
L
(see Note A)
(see Note A)
(see Note A)
See Note B
See Note B
LOAD CIRCUIT FOR
LOAD CIRCUIT FOR
LOAD CIRCUIT FOR
t AND t
PZL PLZ
t , t , AND t
d
r
f
t
AND t
PHZ
PZH
V
CC
50%
CS
0 V
SYSTEM
CLOCK
t
PZL
t
PLZ
V
CC
Output Waveform 1
(see Note C)
50%
See Note B
10%
0 V
t
PZH
t
PHZ
V
OH
90%
Output Waveform 2
(see Note C)
50%
0 V
VOLTAGE WAVEFORMS FOR ENABLE AND DISABLE TIMES
I/O CLOCK
0.8 V
2.4 V
0.4 V
Output
t
d
t
t
f
r
2.4 V
0.8 V
DATA OUT
VOLTAGE WAVEFORMS FOR RISE AND FALL TIMES
VOLTAGE WAVEFORMS FOR DELAY TIME
= 50 pF for TLC540 and 100 pF for TLC541.
NOTES: A.
B.
C
L
en PZH
t
= t
or t
, t
= t
or t
.
PLZ
PZL dis PHZ
C. Waveform 1 is for an output with internal conditions such that the output is low except when disabled by the output control.
Waveform 2 is for an output with internal conditions such that the output is high except when disabled by the output control.
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
APPLICATION INFORMATION
simplified analog input analysis
Using the equivalent circuit in Figure 1, the time required to charge the analog input capacitance from 0 to V
within 1/2 LSB can be derived as follows:
S
The capacitance charging voltage is given by
–t R C
c
t
i
(1)
V
V
1–e
C
S
where
R = R + r
i
t
s
The final voltage to 1/2 LSB is given by
V (1/2 LSB) = V – (V /512)
(2)
C
S
S
Equating equation 1 to equation 2 and solving for time t gives
c
–t R C
c
t
i
V
V
512
V
1–e
(3)
(4)
S
S
S
and
t (1/2 LSB) = R × C × ln(512)
c
t
i
Therefore, with the values given the time for the analog input signal to settle is
t (1/2 LSB) = (R + 1 kΩ) × 60 pF × ln(512)
(5)
c
s
This time must be less than the converter sample time shown in the timing diagrams.
†
Driving Source
TLC540/1
R
r
i
s
V
I
V
S
V
C
1 kΩ MAX
C
i
50 pF MAX
V
V
= Input Voltage at INPUT A0–A10
= External Driving Source Voltage
I
S
s
R = Source Resistance
r
= Input Resistance
i
C = Equivalent Input Capacitance
i
†
Driving source requirements:
•
Noise and distortion for the source must be equivalent to the
resolution of the converter.
•
R must be real at the input frequency.
s
Figure 1. Equivalent Input Circuit Including the Driving Source
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
PRINCIPLES OF OPERATION
The TLC540 and TLC541 are each complete data acquisition systems on a single chip. They include such functions
as analog multiplexer, sample and hold, 8-bit A/D converter, data and control registers, and control logic. For flexibility
and access speed, there are four control inputs [two clocks, chip select (CS), and address]. These control inputs and
a TTL-compatible 3-state output are intended for serial communications with a microprocessor or microcomputer.
With judicious interface timing, with TLC540 a conversion can be completed in 9 µs, while complete
input-conversion-output cycles can be repeated every 13 µs. With TLC541 a conversion can be completed in 17 µs,
while complete input-conversion-output cycles are repeated every 25 µs. Furthermore, this fast conversion can be
executed on any of 11 inputs or its built-in self-test and in any order desired by the controlling processor.
The system and I/O clocks are normally used independently and do not require any special speed or phase
relationships between them. This independence simplifies the hardware and software control tasks for the device.
Once a clock signal within the specification range is applied to SYSTEM CLOCK, the control hardware and software
need only be concerned with addressing the desired analog channel, reading the previous conversion result, and
starting the conversion by using I/O CLOCK. SYSTEM CLOCK will drive the conversion crunching circuitry so that
the control hardware and software need not be concerned with this task.
WhenCSishigh, DATAOUTisina3-stateconditionandADDRESSINPUTandI/OCLOCKaredisabled. Thisfeature
allows each of these terminals, with the exception of CS, to share a control logic point with their counterpart terminals
on additional A/D devices when additional TLC540/541 devices are used. In this way, the above feature serves to
minimize the required control logic terminals when using multiple A/D devices.
The control sequence has been designed to minimize the time and effort required to initiate conversion and obtain
the conversion result. A normal control sequence is:
1. CS is brought low. To minimize errors caused by noise at CS, the internal circuitry waits for two rising edges
and then a falling edge of SYSTEM CLOCK after a low CS transition, before the low transition is recognized.
This technique is used to protect the device against noise when the device is used in a noisy environment.
The MSB of the previous conversion result automatically appears on DATA OUT.
2. A new positive-logic multiplexer address is shifted in on the first four rising edges of I/O CLOCK. The MSB
of the address is shifted in first. The negative edges of these four I/O clock pulses shift out the second, third,
fourth, and fifth most significant bits of the previous conversion result. The on-chip sample and hold begins
sampling the newly addressed analog input after the fourth falling edge. The sampling operation basically
involves the charging of internal capacitors to the level of the analog input voltage.
3. Three clock cycles are then applied to I/O CLOCK and the sixth, seventh, and eighth conversion bits are
shifted out on the negative edges of these clock cycles.
4. The final eighth clock cycle is applied to I/O CLOCK. The falling edge of this clock cycle completes the
analog sampling process and initiates the hold function. Conversion is then performed during the next 36
system clock cycles. After this final I/O clock cycle, CS must go high or the I/O CLOCK must remain low
for at least 36 system clock cycles to allow for the conversion function.
CS can be kept low during periods of multiple conversion. When keeping CS low during periods of multiple
conversion, special care must be exercised to prevent noise glitches on I/O CLOCK. If glitches occur on I/O CLOCK,
the I/O sequence between the microprocessor/controller and the device loses synchronization. Also, if CS is taken
high, itmustremainhighuntiltheendoftheconversion. Otherwise, avalidfallingedgeofCScausesaresetcondition,
which aborts the conversion in progress.
A new conversion can be started and the ongoing conversion simultaneously aborted by performing steps 1 through
4 before the 36 system clock cycles occur. Such action yields the conversion result of the previous conversion and
not the ongoing conversion.
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TLC540I, TLC541I
8-BIT ANALOG-TO-DIGITAL CONVERTERS
WITH SERIAL CONTROL AND 11 INPUTS
SLAS065A – OCTOBER 1983 – REVISED MARCH 1995
PRINCIPLES OF OPERATION
It is possible to connect SYSTEM CLOCK and I/O clock together in special situations in which controlling circuitry
points must be minimized. In this case, the following special points must be considered in addition to the requirements
of the normal control sequence previously described.
1. The first two clocks are required for this device to recognize CS is at a valid low level when the common clock
signal is used as an I/O CLOCK. When CS is recognized by the device to be at a high level, the common clock
signal is used for the conversion clock also.
2. A low CS must be recognized before the I/O CLOCK can shift in an analog channel address. The device
recognizes a CS transition when the SYSTEM CLOCK terminal receives two positive edges and then a
negative edge. For this reason, after a CS negative edge, the first two clock cycles do not shift in the address.
Also, upon shifting in the address, CS must be raised after the eighth valid (10 total) I/O CLOCK. Otherwise,
additional common clock cycles are recognized as I/O CLOCKS and will shift in an erroneous address.
For certain applications, such as strobing applications, it is necessary to start conversion at a specific point in time.
This device accommodates these applications. Although the on-chip sample and hold begins sampling upon the
negative edge of the fourth valid I/O clock cycle, the hold function is not initiated until the negative edge of the eighth
valid I/O clock cycle. Thus, the control circuitry can leave the I/O clock signal in its high state during the eighth valid
I/O clock cycle until the moment at which the analog signal must be converted. The TLC540/TLC541 continues
sampling the analog input until the eighth falling edge of the I/O clock. The control circuitry or software then
immediately lowers the I/O clock signal and holds the analog signal at the desired point in time and start conversion.
Detailed information on interfacing to most popular microprocessors is readily available from the factory.
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Copyright 1999, Texas Instruments Incorporated
相关型号：
TLC540INSG4
IC 11-CH 8-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO20, GREEN, PLASTIC, SO-20, Analog to Digital Converter
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