TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
D
D
D
D
D
D
D
Maximum Throughput 400 KSPS
Built-In Reference and 8× FIFO
Differential/Integral Nonlinearity Error:
±1 LSB
Signal-to-Noise and Distortion Ratio:
69 dB, fi = 12 kHz
Spurious Free Dynamic Range: 75 dB,
fi = 12 kHz
SPI/DSP-Compatible Serial Interfaces With
SCLK up to 20 MHz
Single Supply 5 Vdc
D
D
D
D
D
Analog Input Range 0 V to Supply Voltage
With 500 kHz BW
Hardware Controlled and Programmable
Sampling Period
Low Operating Current (4 mA at 5.5 V
External Ref, 6 mA at 5.5 V, Internal Ref)
Power Down: Software/Hardware
Power-Down Mode (1 µA Max, Ext Ref),
Auto Power-Down Mode (1 µA, Ext Ref)
Programmable Auto-Channel Sweep
D OR PW PACKAGE
DW OR PW PACKAGE
(TOP VIEW)
(TOP VIEW)
SDO
SDI
SCLK
EOC/(INT)
VCC
A0
A1
A2
A3
A4
1
20
2
19
3
18
4
17
5
16
6
15
7
14
8
13
9
12
10
11
CS
REFP
REFM
FS
PWDN
GND
CSTART
A7
A6
A5
SDO
SDI
SCLK
EOC/(INT)
VCC
A0
A1
A2
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
CS
REFP
REFM
FS
PWDN
GND
CSTART
A3
description
The TLC2558 and TLC2554 are a family of high-performance, 12-bit low power, 1.6 µs, CMOS analog-to-digital
converters (ADC) which operate from a single 5 V power supply. These devices have three digital inputs and
a 3-state output [chip select (CS), serial input-output clock (SCLK), serial data input (SDI), and serial data output
(SDO)] that provide a direct 4-wire interface to the serial port of most popular host microprocessors (SPI
interface). When interfaced with a DSP, a frame sync (FS) signal is used to indicate the start of a serial data
frame.
In addition to a high-speed A/D converter and versatile control capability, these devices have an on-chip analog
multiplexer that can select any analog inputs or one of three internal self-test voltages. The sample-and-hold
function is automatically started after the fourth SCLK edge (normal sampling) or can be controlled by a special
pin, CSTART, to extend the sampling period (extended sampling). The normal sampling period can also be
programmed as short (12 SCLKs) or as long (24 SCLKs) to accommodate faster SCLK operation popular
among high-performance signal processors. The TLC2558 and TLC2554 are designed to operate with very low
power consumption. The power-saving feature is further enhanced with software/hardware/auto power down
modes and programmable conversion speeds. The converter uses the external SCLK as the source of the
conversion clock to achieve higher (up to 1.6 µs when a 20 MHz SCLK is used) conversion speed. There is a
4-V internal reference available. An optional external reference can also be used to achieve maximum flexibility.
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.
Copyright 1999, 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.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
functional block diagram
VCC
4V
Reference
REFP
REFM
2554
A0
X
A1
X
A2
X
A3
X
Analog
MUX
2558
A0
A1
A2
A3
A4
A5
A6
A7
FIFO
12 Bit × 8
Low Power
12-BIT
SAR ADC
S/H
Conversion
Clock
Command
Decode
CFR
SDI
M
U
X
SDO
CMR (4 MSBs)
SCLK
CS
FS
CSTART
PWDN
Control Logic
EOC/(INT)
GND
AVAILABLE OPTIONS
PACKAGED DEVICES
TA
2
20-TSSOP
(PW)
20-SOIC
(DW)
16-SOIC
(D)
16-TSSOP
(PW)
0°C to 70°C
TLC2558CPW
TLC2558CDW
TLC2554CD
TLC2554CPW
– 40°C to 85°C
TLC2558IPW
TLC2558IDW
TLC2554ID
TLC2554IPW
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
Terminal Functions
TERMINAL
NAME
A0
A1
A2
A3
A0
A1
A2
A3
A4
A5
A6
A7
CS
NO.
I/O
DESCRIPTION
6
7
8
9
10
11
12
13
I
Analog signal inputs. The analog inputs are applied to these terminals and are internally
multiplexed. The driving source impedance should be less than or equal to 1 kΩ.
20
I
TLC2554
TLC2558
6
7
8
9
16
For a source impedance greater than 1 kΩ, use the asynchronous conversion start signal CSTART
(CSTART low time controls the sampling period) or program long sampling period to increase the
sampling time.
Chip select. A high-to-low transition on the CS input resets the internal 4-bit counter, enables SDI,
and removes SDO from 3-state within a maximum setup time. SDI is disabled within a setup time
after the 4-bit counter counts to 16 (clock edges) or a low-to-high transition of CS whichever
happens first. SDO is 3-stated after the rising edge of CS.
CS can be used as the FS pin when a dedicated serial port is used.
CSTART
10
14
I
EOC/(INT)
4
4
O
This terminal controls the start of sampling of the analog input from a selected multiplex channel.
A high-to-low transition starts sampling of the analog input signal. A low-to-high transition puts the
S/H in hold mode and starts the conversion. This input is independent from SCLK and works when
CS is high (inactive). The low time of CSTART controls the duration of the sampling period of the
converter (extended sampling).
Tie this terminal to VCC if not used.
End of conversion or interrupt to host processor.
[PROGRAMMED AS EOC]: This output goes from a high-to-low logic level at the end of the
sampling period and remains low until the conversion is complete and data are ready for transfer.
EOC is used in conversion mode 00 only.
[PROGRAMMED AS INT]: This pin can also be programmed as an interrupt output signal to the
host processor. The falling edge of INT indicates data are ready for output. The following CS↓ or
FS↑ clears INT. The falling edge of INT puts SDO back to 3-state even if CS is still active.
FS
13
17
I
DSP frame sync input. Indication of the start of a serial data frame in or out of the device. If FS
remains low at the falling edge of CS, SDI is not enabled. A high-to-low transition on the FS input
resets the internal 4-bit counter and enables SDI within a maximum setup time. SDI is disabled
within a setup time after the 4-bit counter counts to 16 (clock edges) or a low-to-high transition of
CS whichever happens first. SDO is 3-stated after the 16th bit is presented.
GND
11
15
I
Ground return for the internal circuitry. Unless otherwise noted, all voltage measurements are with
respect to GND.
PWDN
12
16
I
Both analog and reference circuits are powered down when this pin is at logic zero. The device can
be restarted by active CS or CSTART after this pin is pulled back to logic one.
SCLK
3
3
I
Input serial clock. This terminal receives the serial SCLK from the host processor. SCLK is used
to clock the input SDI to the input register. It is also used as the source of the conversion clock.
SDI
2
2
I
Serial data input. The input data is presented with the MSB (D15) first. The first 4-bit MSBs,
D(15–12) are decoded as one of the 16 commands (12 only for the TLC2554). All trailing blanks
are filled with zeros. The configure write commands require an additional 12 bits of data.
When FS is not used (FS =1), the first MSB (D15) is expected after the falling edge of CS and is
shifted in on the rising edges of SCLK (after CS↓).
When FS is used (typical with an active FS from a DSP) the first MSB (D15) is expected after the
falling edge of FS and is shifted in on the falling edges of SCLK.
Tie this terminal to VCC if not used.
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3
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
Terminal Functions (Continued)
TERMINAL
NAME
SDO
NO.
TLC2554
TLC2558
1
1
I/O
DESCRIPTION
O
The 3-state serial output for the A/D conversion result. SDO is kept in the high-impedance state
when CS is high and after the CS falling edge and until the MSB (D15) is presented. The output
format is MSB (D15) first.
When FS is not used (FS = 1 at the falling edge of CS), the MSB (D15) is presented to the SDO
pin after the CS falling edge, and successive data are available at the rising edge of SCLK.
When FS is used (FS = 0 at the falling edge of CS), the MSB (D15) is presented to SDO after the
falling edge of CS and FS = 0 is detected. Successive data are available at the falling edge of SCLK.
(This is typically used with an active FS from a DSP.)
For conversion and FIFO read cycles, the first 12 bits are the result from the previous conversion
(data) followed by 4 trailing zeros. The first four bits from SDO for CFR read cycles should be
ignored. The register content is in the last 12 bits. SDO is 3 stated after the 16th bit.
REFM
14
18
I
External reference input or internal reference decoupling.
REFP
15
19
I
External reference input or internal reference decoupling. (Shunt capacitors of 10 µF and 0.1 µF
between REFP and REFM.) The maximum input voltage range is determined by the difference
between the voltage applied to this terminal and the REFM terminal when an external reference
is used.
VCC
5
5
I
Positive supply voltage
detailed description
analog inputs and internal test voltages
The 4/8 analog inputs and three internal test inputs are selected by the analog multiplexer depending on the
command entered. The input multiplexer is a break-before-make type to reduce input-to-input noise injection
resulting from channel switching.
pseudo-differential/single-ended input
All analog inputs can be programmed as single-ended or pseudo-differential mode. Pseudo-differential mode
is enabled by setting CFR.D7 – 1. Only three analog input channels (or seven channels for TLC2558) are
available for TLV2554 since one input (A1 for TLC2554 or A2 for TLC2558) is used as the MINUS input when
pseudo-differential mode is used. The minus input pin can have a maximum ±0.2 V ripple. This is normally used
for ground noise rejection.
converter
The TLC2554/58 uses a 12-bit successive approximation ADC and 2-bit resistor string. The CMOS threshold
detector in the successive-approximation conversion system determines each bit by examining the charge on
a series of binary-weighted capacitors (see Figure 1). In the first phase of the conversion process, the analog
input is sampled by closing the SC switch and all ST switches simultaneously. This action charges all the
capacitors to the input voltage.
4
POST OFFICE BOX 655303
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TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
converter (continued)
SC
Threshold
Detector
To Output
Latch
512
256
8
REF+
REF+
4
2
1
1
Node
512
REF–
REF–
ST
REF–
ST
REF+
REF+
REF–
REF–
ST
ST
REF+
2-Bit
R-String
DAC
REF+
REF–
ST
ST
ST
VI
Figure 1. Simplified Model of the Successive-Approximation System
In the next phase of the conversion process the threshold detector begins identifying bits by identifying the
charge (voltage) on each capacitor relative to the reference (REFM) voltage. In the switching sequence, ten
capacitors are examined separately until all ten bits are identified and the charge-convert sequence is repeated.
In the first step of the conversion phase, the threshold detector looks at the first capacitor (weight = 512). Node
512 of this capacitor is switched to the REFP voltage, and the equivalent nodes of all the other capacitors on
the ladder are switched to REFM. If the voltage at the summing node is greater than the trip point of the threshold
detector (approximately one-half the VCC voltage), a bit 0 is placed in the output register and the 512-weight
capacitor is switched to REFM. If the voltage at the summing node is less than the trip point of the threshold
detector, a bit 1 is placed in the register. The 512-weight capacitor remains connected to REFP through the
remainder of the successive-approximation process. The process is repeated for the 1024-weight capacitor,
the 128-weight capacitor, and so forth down the line until all bits are counted.
With each step of the successive-approximation process, the initial charge is redistributed among the
capacitors. The conversion process relies on charge redistribution to count and weigh the bits from MSB to LSB.
serial interface
INPUT DATA FORMAT
MSB
LSB
D15–D12
D11–D0
Command
Configuration data field
Input data is binary. All trailing blanks can be filled with zeros.
OUTPUT DATA FORMAT READ CFR
MSB
LSB
D15–D12
D11–D0
Don’t care
Register content
OUTPUT DATA FORMAT CONVERSION/READ FIFO
MSB
LSB
D15–D4
Conversion result
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All zeros
• DALLAS, TEXAS 75265
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TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
serial interface (continued)
The output data format is either binary (unipolar straight binary) or 2s complement.
binary
Zero scale code = 000h, Vcode = VREFM
Full scale code = FFFh, Vcode = VREFP – 1 LSB
2’s complement
Minus full scale code = 800h, Vcode = VREFM
Full scale code = 7FFh, Vcode = VREFP – 1 LSB
control and timing
start of the cycle:
D
D
When FS is not used ( FS = 1 at the falling edge of CS), the falling edge of CS is the start of the cycle. Input
data is shifted in on the rising edge, and output data changes on the falling edge of SCLK. This is typically
used for a SPI microcontroller, although it can also be used for a DSP.
When FS is used ( FS is an active signal from a DSP), the falling edge of FS is the start of the cycle. Input
data is shifted in on the falling edge, and output data changes on the rising edge of SCLK. This is typically
used for a TMS320 DSP.
first 4-MSBs: the command register (CMR)
The TLC2554/TLC2558 have a 4-bit command set (see Table 1) plus a 12-bit configuration data field. Most of
the commands require only the first 4 MSBs, i.e. without the 12-bit data field.
NOTE:
The device requires a write CFR (configuration register) with 000h data (write A000h to the serial
input) at power up to initialize host select mode.
The valid commands are listed in Table 1.
Table 1. TLC2554/TLC2558 Command Set
SDI D(15–12) BINARY, HEX
6
TLC2558 COMMAND
TLC2554 COMMAND
0000b
0000h
Select analog input channel 0
Select analog input channel 0
0001b
1000h
Select analog input channel 1
N/A
0010b
2000h
Select analog input channel 2
Select analog input channel 1
0011b
3000h
Select analog input channel 3
N/A
0100b
4000h
Select analog input channel 4
Select analog input channel 2
0101b
5000h
Select analog input channel 5
N/A
0110b
6000h
Select analog input channel 6
Select analog input channel 3
0111b
7000h
Select analog input channel 7
N/A
1000b
8000h
SW power down (analog + reference)
1001b
9000h
Read CFR register data shown as SDO D(11–0)
1010b
A000h plus data
Write CFR followed by 12-bit data
1011b
B000h
Select test, voltage = (REFP+REFM)/2
1100b
C000h
Select test, voltage = REFM
1101b
D000h
Select test, voltage = REFP
1110b
E000h
FIFO read, FIFO contents shown as SDO D(15–4), D(3–0) = 0000
1111b
F000h plus data
Reserved
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TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
control and timing (continued)
configuration
Configuration data is stored in one 12-bit configuration register (CFR) (see Table 2 for CFR bit definitions). Once
configured after first power up, the information is retained in the H/W or S/W power-down state. When the device
is being configured, a write CFR cycle is issued by the host processor. This is a 16-bit write. If the SCLK stops
after the first 8 bits are entered, then the next eight bits can be taken after the SCLK is resumed. The status of
the CFR can be read with a read CFR command.
Table 2. TLC2554/TLC2558 Configuration Register (CFR) Bit Definitions
BIT
DEFINITION
D(15–12)
All zeros, nonprogrammable
D11
Reference select
0: External
1: Internal
D10
Output select
0: Unipolar straight binary
1: 2’s complement
D9
Sample period select
0: Short sampling 12 SCLKs (1x sampling time)
1: Long sampling 24 SCLKs (2x sampling time)
D8
Conversion clock source select
0: Conversion clock = SCLK
1: Conversion clock = SCLK/2
D7
Input select
0: Normal
1: Pseudo differential CH A2(2558) or CH A1 (2554) is the differential input
D(6,5)
Conversion mode select
00: Single shot mode
01: Repeat mode
10: Sweep mode
11: Repeat sweep mode
D(4,3)†
TLC2558
Sweep auto sequence select
00: 0–1–2–3–4–5–6–7
01: 0–2–4–6–0–2–4–6
10: 0–0–2–2–4–4–6–6
11: 0–2–0–2–0–2–0–2
TLC2554
Sweep auto sequence select
00: N/A
01: 0–1–2–3–0–1–2–3
10: 0–0–1–1–2–2–3–3
11: 0–1–0–1–0–1–0–1
D2
EOC/INT – pin function select
0: Pin used as INT
1: Pin used as EOC
D(1,0)
FIFO trigger level (sweep sequence length)
00: Full (INT generated after FIFO level 7 filled)
01: 3/4 (INT generated after FIFO level 5 filled)
10: 1/2 (INT generated after FIFO level 3 filled)
11: 1/4 (INT generated after FIFO level 1 filled)
† These bits only take effect in conversion modes 10 and 11.
sampling
The sampling period starts after the first 4 input data are shifted in if they are decoded as one of the conversion
commands. These are select analog input (channel 0 through 7) and select test (channel 1 through 3).
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TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
normal sampling
When the converter is using normal sampling, the sampling period is programmable. It can be 12 SCLKs (short
sampling) or 24 SCLKs (long sampling). Long sampling helps the input analog signal sampled to settle to 0.5
LSB accuracy when input source resistance is high.
extended sampling
An asynchronous (to the SCLK) signal, via dedicated hardware pin CSTART, can be used in order to have total
control of the sampling period and the start of a conversion. This is extended sampling. The falling edge of
CSTART is the start of the sampling period. The rising edge of CSTART is the end of the sampling period and
the start of the conversion. This function is useful for an application that requires:
D
D
The use of an extended sampling period to accommodate different input source impedance.
The use of a faster I/O clock on the serial port but not enough sampling time is available due to the fixed
number of SCLKs. This could be due to a high input source impedance or due to higher MUX ON resistance
at lower supply voltage (refer to application information).
Once the conversion is complete, the processor can initiate a read cycle using either the read FIFO command
to read the conversion result or simply select the next channel number for conversion. Since the device has a
valid conversion result in the output buffer, the conversion result is simply presented at the serial data output.
TLC2554/TLC2558 conversion modes
The TLC2554 and TLC2558 have four different conversion modes (mode 00, 01, 10, 11). The operation of each
mode is slightly different, depending on how the converter performs the sampling and which host interface is
used. The trigger for a conversion can be an active CSTART (extended sampling), CS (normal sampling, SPI
interface), or FS (normal sampling, TMS320 DSP interface). When FS is used as the trigger, CS can be held
active, i.e. CS does not need to be toggled through the trigger sequence. Different types of triggers should not
be mixed throughout the repeat and sweep operations. When CSTART is used as the trigger, the conversion
starts on the rising edge of CSTART. The minimum low time for CSTART is 800 ns. If an active CS or FS is used
as the trigger, the conversion is started after the 16th or 28th SCLK edge. Enough time (for conversion) should
be allowed between consecutive triggers so that no conversion is terminated prematurely.
one shot mode (mode 00)
One shot mode (mode 00) does not use the FIFO, and the EOC is generated as the conversion is in progress
(or INT is generated after the conversion is done).
repeat mode (mode 01)
Repeat mode (mode 01) uses the FIFO. Once the programmed FIFO threshold is reached, the FIFO must be
read, or the data is lost and the sequence starts over again. This allows the host to set up the converter and
continue monitoring a fixed input and come back to get a set of samples when preferred. The first conversion
must start with a select command so an analog input channel can be selected.
sweep mode (mode 10)
Sweep mode (mode 10) also uses the FIFO. Once it is programmed in this mode, all of the channels listed in
the selected sweep sequence are visited in sequence. The results are converted and stored in the FIFO. This
sweep sequence may not be completed if the FIFO threshold is reached before the list is completed. This allows
the system designer to change the sweep sequence length. Once the FIFO has reached its programmed
threshold, an interrupt (INT) is generated. The host must issue a read FIFO command to read and clear the FIFO
before the next sweep can start.
8
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TLC2554/TLC2558 conversion modes (continued)
repeat sweep mode (mode 11)
Repeat sweep mode (mode 11) works the same way as mode 10 except the operation has an option to continue
even if the FIFO threshold is reached. Once the FIFO has reached its programmed threshold, an interrupt (INT)
is generated. Then two things may happen:
1. The host may choose to act on it (read the FIFO) or ignore it. If the next cycle is a read FIFO cycle, all of
the data stored in the FIFO is retained until it has been read in order.
2. If the next cycle is not a read FIFO cycle, or another CSTART is generated, all of the content stored in the
FIFO is cleared before the next conversion result is stored in the FIFO, and the sweep is continued.
Table 3. TLC2554/TLC2558 Conversion Mode
CONVERSION
MODE
One shot
Repeat
Sweep
Repeat sweep
CFR
D(6,5)
00
01
10
11
SAMPLING
TYPE
OPERATION
Normal
•
•
•
•
Single conversion from a selected channel
CS or FS to start select/sampling/conversion/read
One INT or EOC generated after each conversion
Host must serve INT by selecting channel, and converting and reading the previous output.
Extended
•
•
•
•
•
Single conversion from a selected channel
CS to select/read
CSTART to start sampling and conversion
One INT or EOC generated after each conversion
Host must serve INT by selecting next channel and reading the previous output.
Normal
•
•
•
•
Repeated conversions from a selected channel
CS or FS to start sampling/conversion
One INT generated after FIFO is filled up to the threshold
Host must serve INT by either 1) (FIFO read) reading out all of the FIFO contents up to the
threshold, then repeat conversions from the same selected channel or 2) writing another
command(s) to change the conversion mode. If the FIFO is not read when INT is served, it
is cleared.
Extended
•
Same as normal sampling except CSTART starts each sampling and conversion when CS is
high.
Normal
•
•
•
•
One conversion per channel from a sequence of channels
CS or FS to start sampling/conversion
One INT generated after FIFO is filled up to the threshold
Host must serve INT by (FIFO read) reading out all of the FIFO contents up to the threshold,
then write another command(s) to change the conversion mode.
Extended
•
Same as normal sampling except CSTART starts each sampling and conversion when CS is
high.
Normal
•
•
•
•
Repeated conversions from a sequence of channels
CS or FS to start sampling/conversion
One INT generated after FIFO is filled up to the threshold
Host must serve INT by either 1) (FIFO read) reading out all of the FIFO contents up to the
threshold, then repeat conversions from the same selected channel or 2) writing another
command(s) to change the conversion mode. If the FIFO is not read when INT is served it is
cleared.
Extended
•
Same as normal sampling except CSTART starts each sampling and conversion when CS is
high.
NOTE: Programming the EOC/INT pin as the EOC signal works for mode 00 only. The other three modes automatically generate an INT signal
irrespective of whether EOC/INT is programmed.
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SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
timing diagrams
The timing diagrams can be categorized into two major groups: nonconversion and conversion. The
nonconversion cycles are read and write (configuration). None of these cycles carry a conversion. Conversion
cycles are those four modes of conversion.
read cycle (read FIFO or read CFR)
read CFR cycle:
The read command is decoded in the first 4 clocks. SDO outputs the contents of the CFR after the 4th SCLK.
1
2
3
4
5
7
6
12
13
14
15
16
1
SCLK
CS
FS
SDI
INT
EOC
SDO
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎ
ID15
ID14
ID13
ID12
ID15
OD11 OD10
OD9
OD4
OD3
OD2
OD1
OD0
Figure 2. TLC2554/TLC2558 Read CFR Cycle (FS active)
1
2
3
4
ID14
ID13
ID12
5
6
7
12
13
14
15
16
1
SCLK
CS
FS
SDI
INT
EOC
SDO
ÎÎÎ
ÎÎÎ
ID15
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ID15
ÎÎÎÎÎÎ
OD11 OD10
OD9
OD4
OD3
OD2
OD1
OD0
Figure 3. TLC2554/TLC2558 Read CFR Cycle (FS = 1)
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ÎÎÎÎ
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5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
read cycle (read FIFO or read CFR) (continued)
FIFO read cycle
The first command in the active cycle after INT is generated, if the FIFO is used, is assumed as the FIFO read
command. The first FIFO content is output immediately before the command is decoded. If this command is
not a FIFO read, then the output is terminated but the first data in the FIFO is retained until a valid FIFO read
command is decoded. Use of more layers of the FIFO reduces the time taken to read multiple data. This is
because the read cycle does not generate EOC or INT nor does it carry out any conversion.
1
2
3
4
ID14
ID13
ID12
OD11 OD10
OD9
OD8
5
6
7
12
13
14
15
16
1
SCLK
CS
ÎÎÎ
ÎÎÎ
FS
SDI
ID15
INT
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ID15
EOC
SDO
OD7 OD6
OD5
OD0
Figure 4. TLC2554/TLC2558 Continuous FIFO Read Cycle (FS = 1)
(controlled by SCLK, SCLK can stop between each 16 SCLKs)
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ID14
ÎÎÎ
ÎÎÎ
11
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
write cycle (write CFR)
The write cycle is used to write to the configuration register CFR (with 12-bit register content). The write cycle
does not generate an EOC or INT nor does it carry out any conversion.
1
2
3
4
5
6
ID11
ID10
7
12
13
14
15
16
1
SCLK
CS
ÎÎÎÎ
ÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
FS
SDI
ID15
ID14
ID13
ID12
ID9
ID4
ID3
ID2
ID1
ID0
ID15
INT
EOC
SDO
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
Figure 5. TLC2554/TLC2558 Write Cycle (FS active)
1
2
3
4
5
6
7
12
13
ID15
ID14
ID13
ID12
ID11
ID10
ID9
ID4
ID3
14
15
16
ID1
ID0
ÎÎÎÎÎ
ÎÎÎÎÎ
1
SCLK
CS
FS
SDI
INT
EOC
SDO
ÎÎÎ
ÎÎÎ
ID2
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
Figure 6. TLC2554/TLC2558 Write Cycle (FS = 1)
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ID15
ID14
ÎÎÎÎ
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
conversion cycles
DSP/normal sampling
1
2
3
4
ID13
ID12
5
6
7
12
13
14
15
16
28
1
SCLK
CS
ÎÎÎ
ÎÎÎ
FS
SDI
ID15
ID14
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎ
ID15
INT
tsample (Long)
tconv
tsample (Short)
EOC
t conv
SDO
OD10 OD9 OD8
OD11
OD7
OD6
OD5
OD0
Figure 7. Mode 00 Single Shot/Normal Sampling (FS signal used)
1
2
3
4
5
6
7
12
13
14
15
16
ÎÎÎÎÎ
ÎÎÎÎÎ
28
1
SCLK
CS
ÎÎÎ
ÎÎÎ
FS
SDI
ID15
ID14
ID13
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎ
ID12
INT
ID14
tsample (Long)
tconv
tsample (Short)
EOC
t conv
SDO
ID15
OD11 OD10 OD9
OD8
OD7
OD6 OD5
OD0
ÎÎÎÎ
ÎÎÎÎ
Figure 8. Mode 00 Single Shot/Normal Sampling (FS = 1, FS signal not used)
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conversion cycles (continued)
Select/Read
Cycle
Select/Read
Cycle
CS
tsample
CSTART
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
FS
tconvert
†
SDI
INT
EOC
SDO
Previous Conversion
Result
Hi-Z
Previous Conversion
Result
Hi-Z
Hi-Z
† This is one of the single shot commands. Conversion starts on next rising edge of CSTART.
Figure 9. Mode 00 Single Shot/Extended Sampling (FS signal used, FS pin connected to TMS320 DSP)
CS used as FS input
When interfacing with the TMS320 DSP using conversion mode 00, the FSR signal from the DSP may be
connected to the CS input if this is the only device on the serial port. This will save one output pin from the DSP.
Output data is made available on the rising edge of SCLK and input data is latched on the rising edge of SCLK
in this case.
modes using the FIFO: modes 01, 10, 11 timing
Modes 01, 10, and 11 timing are very similar except for how and when the FIFO is read, how the device is
configured, and how channel(s) are selected.
Mode 01 (repeat mode) requires a two-cycle configuration where the first one sets the mode and the second
one selects the channel. Once the FIFO is filled up to the threshold programmed, it has the option to either read
the FIFO or configure for other modes. Therefore, the sequence is either configure: select : triggered
conversions : FIFO read : select : triggered conversions : FIFO read or configure : select : triggered conversions
: configure : .... Each configure clears the FIFO and the action that follows the configure command depends on
the mode setting of the device.
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modes using the FIFO: modes 01, 10, 11 timing (continued)
Configure Select
Conversion #1
From Channel 2
Conversion #4
From Channel 2
Select
CS
FS
tsample
tsample
tsample
tconvert
tconvert
tconvert
CSTART
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
†
SDI
§
‡
‡
‡
‡
§
INT
Hi-Z
Hi-Z
SDO
Read FIFO
#1
Top of FIFO
#2
#3
#4
Next #1
† Command = Configure write for mode 01, FIFO threshold = 1/2
‡ Command = Read FIFO, 1st FIFO read
§ Command = Select ch2.
Figure 10. TLC2554/TLC2558 Mode 01 DSP Serial Interface (conversions triggered by FS)
Conversion #1
From Channel 2
Conversion #4
From Channel 2
Configure Select
Select
CS
FS
(DSP)
tsample(2)
tsample(1)
tsample(3)
tsample(4)
CSTART
tconvert(1)
tconvert(2)
tconvert(4)
tconvert(3)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎ
SDI
†
§
‡
‡
‡
‡
§
INT
SDO
Hi-Z
Hi-Z
tSample(i) > = MIN(tSample)
Read FIFO
#1
#2
First FIFO Read
#3
#4
Next #1
† Command = Configure write for mode 01, FIFO threshold = 1/2
‡ Command = Read FIFO, 1st FIFO read
§ Command = Select ch2.
Figure 11. TLC2554/TLC2558 Mode 01 µp/DSP Serial Interface (conversions triggered by CSTART)
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modes using the FIFO: modes 01, 10, 11 timing (continued)
Mode 10 (sweep mode) requires reconfiguration at the start of each new sweep sequence. Once the FIFO is
filled up to the programmed threshold, the host has the option to either read the FIFO or configure for other
modes. Once the FIFO is read, the host must reconfigure the device before the next sweep sequence can be
started. So the sequence is either configure : triggered conversions : FIFO read : configure. or configure :
triggered conversions : configure : .... Each configure clears the FIFO and the action that follows the configure
command depends on the mode setting of the device.
Mode 11 (repeat sweep mode) requires one cycle configuration. This sweep sequence can be repeated without
reconfiguration. Once the FIFO is filled up to the programmed threshold, the host has the option to either read
the FIFO or configure for other modes. So the sequence is either configure : triggered conversions : FIFO read
: triggered conversions : FIFO read ... or configure : triggered conversions : configure : .... Each configure clears
the FIFO and the action that follows the configure command depends on the mode setting of the device.
Conversion
From Channel 0
Configure
Conversion
From Channel 3
Conversion
From Channel 0
Conversion
From Channel 3
CS
tsample(3)
tsample(2)
tsample(4)
tsample(1)
FS
(DSP)
tconvert
tconvert
CSTART
SDI
INT
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
tSample(i) > = MIN(tSample)
‡
†
‡
‡
‡
‡
SDO
Repeat
Read FIFO
#1
#2
#3
Top of FIFO
First FIFO Read
#4
Repeat
Read FIFO
Second FIFO Read
† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.
‡ Command = Read FIFO
Figure 12. TLC2554/TLC2558 Mode 10/11 DSP Serial Interface (conversions triggered by FS)
16
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#1
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5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
modes using the FIFO: modes 01, 10, 11 timing (continued)
Conversion
From Channel 0
Conversion
From Channel 3
Conversion
From Channel 0
Configure
Conversion
From Channel 3
CS
tsample(i) >= MIN (tsample)
FS
(DSP)
CSTART
tsample (1)
tsample (2)
tsample (3)
tsample (4)
tconvert
SDI
INT
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎ
tconvert
‡
†
‡
‡
‡
#3
#4
‡
SDO
Read FIFO
Repeat
#1
#2
Top of FIFO
Repeat
Read FIFO
#1
Second FIFO Read
First FIFO Read
† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.
‡ Command = Read FIFO
Figure 13. TLC2554/TLC2558 Mode 10/11 DSP Serial Interface (conversions triggered by CSTART)
Conversion
From Channel 0
Conversion
From Channel 3
Conversion
From Channel 0
Conversion
From Channel 3
Configure
CS
tsample(1)
tsample(2)
tsample(3)
tsample(4)
tconvert
tconvert
tSample (i) > = MIN(tSample)
CSTART
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
SDI
‡
†
‡
‡
‡
‡
INT
SDO
Read FIFO
Repeat
#1
#2
#3
Top of FIFO
First FIFO Read
#4
Read FIFO
#1
Repeat
Second FIFO Read
† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.
‡ Command = Read FIFO
Figure 14. TLC2554/TLC2558 Mode 00/11 µp Serial Interface (conversions triggered by CS)
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FIFO operation
Serial
OD
12-BIT×8
FIFO
ADC
7
6
FIFO Full
5
4
3
2
1
0
FIFO 1/2 Full
FIFO 3/4 Full
FIFO 1/4 Full
FIFO Threshold Pointer
Figure 15. TLC2554/TLC2558 FIFO
The device has an 8 layer FIFO that can be programmed for different thresholds. An interrupt is sent to the host
after the preprogrammed threshold is reached. The FIFO can be used to store data from either a fixed channel
or a series of channels based on a preprogrammed sweep sequence. For example, an application may require
eight measurements from channel 3. In this case, the FIFO is filled with 8 data sequentially taken from channel
3. Another application may require data from channel 0, channel 2, channel 4, and channel 6 in an orderly
manner. Therefore, the threshold is set for 1/2 and the sweep sequence 0–2–4–6–0–2–4–6 is chosen. An
interrupt is sent to the host as soon as all four data are in the FIFO.
SCLK and conversion speed
There are multiple ways to adjust the conversion speed. The maximum equivalent conversion clock (fSCLK/DIV)
should not exceed 10 MHz.
D
The SCLK is used as the source of the conversion clock and 14 conversion clocks are required to complete
a conversion plus 4 SCLKs overhead.
The devices can operate with an SCLK up to 20 MHz for the supply voltage range specified. The clock
divider provides speed options appropriate for an application where a high speed SCLK is used for faster
I/O. The total conversion time is 14 × (DIV/fSCLK) where DIV is 1 or 2. For example a 20-MHz SCLK with the
divide by 2 option produces a {14 × (2/20 M) + 4 × (1/20 MHz)} = 1.6 µs conversion time.
D
Auto power down can be used. This mode is always on. If the device is not accessed (by CS or CSTART),
the converter is powered down to save power. The built-in reference is left on in order to quickly resume
operation within one half SCLK period. This provides unlimited choices to trade speed with power savings.
reference voltage
The device has a built-in reference with a level of 4 V. If the internal reference is used, REFP is set to 4 V and
REFM is set to 0 V. An external reference can also be used through two reference input pins, REFP and REFM,
if the reference source is programmed as external. The voltage levels applied to these pins establish the upper
and lower limits of the analog inputs to produce a full-scale and zero-scale reading respectively. The values of
REFP, REFM, and the analog input should not exceed the positive supply or be lower than GND consistent with
the specified absolute maximum ratings. The digital output is at full scale when the input signal is equal to or
higher than REFP and at zero when the input signal is equal to or lower than REFM.
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SLAS220A –JUNE 1999
FIFO operation (continued)
power down
Writing 8000h to the device puts the device into a software power-down state. For a hardware power down, the
dedicated PWDN pin provides another way to power down the device asynchronously. These two power-down
modes power down the entire device including the built-in reference to save power. It requires 20 ms to resume
from either a software or hardware power down.
Auto power down mode is always enabled. This mode maintains the built-in reference if an internal reference
is used, so resumption is fast enough to be used between cycles.
The configuration register is not affected by any of the power down modes but the sweep operation sequence
has to be started over again. All FIFO contents are cleared by the power-down modes.
power up and initialization
Initialization requires:
1. Determine processor type by writing A000h to the TLC2554/58
2. Configure the device
The first conversion after power up or resuming from power down is not valid.
absolute maximum ratings over operating free-air temperature (unless otherwise noted)†
Supply voltage range, GND to VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 6.5 V
Analog input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VCC + 0.3 V
Reference input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC + 0.3 V
Digital input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VCC + 0.3 V
Operating virtual junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 150°C
Operating free-air temperature range, TA: TLC2554/58C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
TLC2554/58I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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.
recommended operating conditions
Supply voltage, VCC
MIN
NOM
MAX
4.5
5
5.5
V
VCC
2
V
VCC VCC+0.2
VCC
V
Positive external reference voltage input, VREFP (see Note 1)
Negative external reference voltage input, VREFM (note Note 1)
2
Differential reference voltage input, VREFP – VREFM (see Note 1)
2
Analog input voltage (see Note 1)
0
0
High level control input voltage, VIH
2.1
Low-level control input voltage, VIL
UNIT
V
V
V
0.6
V
Rise time, for CS, CSTART SDI at 0.5 pF, tr(I/O)
4.76
ns
Fall time, for CS, CSTART SDI at 0.5 pF, tf(I/O)
2.91
ns
Rise time, for INT, EOC, SDO at 30 pF, tr(Output)
2.43
ns
Fall time, for INT, EOC, SDO at 30 pF, tf(Output)
2.3
ns
NOTE 1: When binary output format is used, analog input voltages greater than that applied to REFP convert as all ones (111111111111), while
input voltages less than that applied to REFM convert as all zeros (000000000000). The device is functional with reference down to
2 V (VREFP – VREFM –1); however, the electrical specifications are no longer applicable.
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recommended operating conditions (continued)
MIN
Transition time, for FS, SCLK, SDI, tt(CLK)
Setup time, CS falling edge before SCLK rising edge (FS=1) or before SCLK falling edge (when FS is active),
tsu(CS-SCLK)
Hold time, CS rising edge after SCLK rising edge (FS=1) or after SCLK falling edge (when FS is active),
th(SCLK-CS)
Delay time, delay from CS falling edge to FS rising edge, td(CSL-FSH)
Delay time, delay time from 16th SCLK falling edge to CS rising edge (FS is active), td(SCLK16F-CSH)
NOM
MAX
UNIT
0.5
SCLK
0.5
SCLK
5
0.5
ns
7
0.5
Setup time, FS rising edge before SCLK falling edge, tsu(FSH-SCLKF)
SCLKs
SCLKs
0.5
SCLKs
Hold time, FS hold high after SCLK falling edge, th(FSH-SCLKF)
0.5
SCLKs
Pulse width, CS high time, twH(CS)
100
ns
SCLK cycle time, VCC = 2.7 V to 3.6V, tc(SCLK)
67
ns
SCLK cycle time, VCC = 4.5 V to 5.5V, tc(SCLK)
Pulse width, SCLK low time, twL(SCLK)
50
20
30
ns
Pulse width, SCLK high time, twH(SCLK)
20
30
ns
25
ns
ns
Setup time, SDI valid before falling edge of SCLK (FS is active) or the rising edge of SCLK (FS=1),
tsu(DI-SCLK)
Hold time, SDI hold valid after falling edge of SCLK (FS is active) or the rising edge of SCLK (FS=1),
th(DI-SCLK)
Delay time, delay from CS falling edge to SDO valid, td(CSL-DOV)
5
1
25
ns
Delay time, delay from FS falling edge to SDO valid, td(FSL-DOV)
1
25
ns
Delay time, delay from SCLK rising edge (FS is active) or SCLK falling edge (FS=1) SDO valid, td(CLK-DOV)
1
25
ns
Delay time, delay from CS rising edge to SDO 3-stated, td(CSH-DOZ)
1
25
ns
Delay time, delay from 16th SCLK falling edge (FS is active) or the 16th rising edge (FS=1) to EOC falling
edge, td(CLK-EOCL)
1
25
ns
Delay time, delay from EOC rising edge to SDO 3-stated if CS is low, td(EOCH-DOZ)
1
50
ns
3.5
µs
50
ns
Delay time, delay from 16th SCLK rising edge to INT falling edge (FS =1) or from the 16th falling edge SCLK
to INT falling edge (when FS active), td(SCLK-INTL)
Delay time, delay from CS falling edge to INT rising edge, td(CSL-INTH)
Delay time, delay from CS rising edge to CSTART falling edge, td(CSH-CSTARTL)
Delay time, delay from CSTART rising edge to EOC falling edge, td(CSTARTH-EOCL)
Pulse width, CSTART low time, twL(CSTART)
1
ns
100
1
ns
50
Delay time, delay from CS rising edge to EOC rising edge, td(CSH-EOCH)
1
Delay time, delay from CSTART rising edge to CSTART falling edge, td(CSTARTH-CSTARTL)
3.6
Delay time, delay from CSTART rising edge to INT falling edge, td(CSTARTH-INTL)
3.5
TLC2554C/TLC2558C
free air temperature,
temperature TA
Operating free-air
TLC2554I/TLC2558I
ns
µs
0.8
50
ns
µs
µs
0
70
–40
85
_C
NOTE 2: This is the time required for the clock input signal to fall from VIH max or to rise from VILmax to VIHmin. In the vicinity of normal room
temperature, the devices function with input clock transition time as slow as 1 µs for remote data-acquisition applications where the
sensor and A/D converter are placed several feet away from the controlling microprocessor.
20
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
electrical characteristics over recommended operating free-air temperature range, VCC = VREFP = 4.5 V to
5.5 V, SCLK frequency = 20 MHz at 5 V, (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP†
MAX
UNIT
VOH
High-level output voltage
VCC = 5.5 V, IOH = –20 µA at 30 pF load
VOL
Low-level output voltage
VCC = 5.5 V, IOL = 20 µA at 30 pF load
IOZ
O s a e ou
Off-state
output
u cu
current
e
(high-impedance-state)
VO = 0
IIH
High-level input current
IIL
Low-level input current
O e a g supply
Operating
su y current,
cu e , normal
o a sampling
sa
g
(short)
CS at 0 V, Ext ref
VCC = 4.5 V to 5.5 V
CS at 0 V, Int ref
VCC = 4.5 V to 5.5 V
CS at 0 V, Ext ref
VCC = 4.5 V to 5.5 V
1.9
mA
CS at 0 V, Int ref
VCC = 4.5 V to 5.5 V
2
mA
ICC
ICC
VO = VCC
Operating supply current,
current extended sampling
ICC(PD)
ICC(AUTOPWDN)
1
2.5
-2.5
VI = VCC
0.005
2.5
VI = 0 V
–0.005
2.5
µA
4
mA
6
mA
Power-down supply current
For all digital inputs,
0≤ VI ≤ 0.3 V or VI ≥ VCC– 0.3 V,
SCLK = 0, VCC = 4.5 V to 5.5 V,
Ext clock
Auto power-down current
For all digital inputs,
0≤ VI ≤ 0.3 V or VI ≥ VCC– 0.3 V,
SCLK = 0, VCC = 4.5 V to 5.5 V,
Ext clock, Ext ref
Ci
Input capacitance
Zi
Input MUX ON resistance
V
–1
CS at 0 V, VCC = 4.5 V to 5.5 V
Maximum static analog reference current into
REFP (use external reference)
V
0.4
CS = VCC
Internal reference supply current
Selected channel leakage current
2.4
0.1
mA
1
µA
5‡
µA
1
Selected channel at 0 V
–1
1
Analog inputs
45
50
Control Inputs
5
25
VCC = 5.5 V
µA
2
Selected channel at VCC
VREFP = VCC = 5.5 V, VREFM = GND
µA
500
µA
µA
pF
Ω
† All typical values are at VCC = 5 V, TA = 25°C.
‡ 800 µA if internal reference is used.
ac specifications
PARAMETER
SINAD
Signal-to-noise ratio +distortion
THD
Total harmonic distortion
ENOB
Effective number of bits
SFDR
Spurious free dynamic range
TEST CONDITIONS
MIN
fI = 12 kHz at 400 KSPS
fI = 12 kHz at 400 KSPS
69
fI = 12 kHz at 400 KSPS
fI = 12 kHz at 400 KSPS
TYP
MAX
71
–82
dB
–76
11.6
–84
UNIT
dB
Bits
–75
dB
Analog input
Full power bandwidth, –3 dB
1
MHz
Full power bandwidth, –1 dB
500
kHz
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
21
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
reference specifications (0.1 µF and 10 µF between REFP and REFM pins)
PARAMETER
TEST CONDITIONS
Reference input voltage, REFP
VCC = 4.5 V
Input impedance
VCC = 5
5V
5.5
Input voltage difference, REFP – REFM
VCC = 4.5 V
VCC = 5.5 V
Internal reference voltage,REFP – REFM
Internal reference start up time
VCC = 5.5 V
VCC = 4.5 V
Reference temperature coefficient
CS = 1,
SCLK = 0, (off)
CS = 0,
SCLK = 20 MHz (on)
MIN
TYP
UNIT
VCC
V
100
MΩ
20
25
2
Reference select = internal
MAX
3.85
4
10 µF
kΩ
VCC
4.15
20
16
V
V
ms
40 PPM/°C
operating characteristics over recommended operating free-air temperature range, VCC = VREFP = 4.5 V,
SCLK frequency = 20 MHz (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP†
Integral linearity error (INL) (see Note 4)
Differential linearity error (DNL)
See Note 3
EO
EG
Offset error (see Note 5)
See Note 3
Gain error (see Note 5)
See Note 3
ET
Total unadjusted error (see Note 6)
Self-test output code (see Table 1 and Note 7)
tconv
Conversion time
tsample
tt(I/O)
Sampling time
±1
SDI = B000h
800h
(2048D)
SDI = C000h
000h
(0D)
SDI = D000h
FFFh
(4095D)
MAX
UNIT
±1
LSB
±1
LSB
±2.5
LSB
±2
LSB
±2
LSB
(14XDIV)
fSCLK
External SCLK
At 1 kΩ
Transition time for EOC, INT
600
ns
50
ns
tt(CLK)
Transition time for SDI, SDO
25
ns
† All typical values are at TA = 25°C.
NOTES: 3. Analog input voltages greater than that applied to REFP convert as all ones (111111111111), while input voltages less than that
applied to REFM convert as all zeros (0000000000). The device is functional with reference down to 2 V (VREFP – VREFM);
however, the electrical specifications are no longer applicable.
4. Linear error is the maximum deviation from the best straight line through the A/D transfer characteristics.
5. Zero error is the difference between 000000000000 and the converted output for zero input voltage: full-scale error is the difference
between 111111111111 and the converted output for full-scale input voltage.
6. Total unadjusted error comprises linearity, zero, and full-scale errors.
7. Both the input data and the output codes are expressed in positive logic.
22
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PARAMETER MEASUREMENT INFORMATION
tt(I/O)
90%
50%
10%
CS
tt(I/O)
VIH
VIL
twH(CS)
td(CSL-FSH)
VIH
FS
VIL
tsu(FSH-SCLKF)
th(FSH-SCLKF)
td(SCLK16F-CSH)
twH(SCLK)
twL(SCLK)
th(SCLK-CS)
tsu(CS-SCLK)
1
16
VIH
SCLK
tc(SCLK)
VIL
tsu(DI-CLK)
ÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎ
SDI
td(FSL-DOV)
td(CSL-DOV)
th(DI-CLK)
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
VIH
ID15
ID1
VIL
td(CLK-DOV)
VOH
Hi-Z
SDO
VOL
td(CLK-EOCL)
td(EOCH–DOZ)
VOH
EOC
VOL
td(SCLK-INTL)
td(CSL-INTH)
VOH
INT
VOL
Figure 16. Critical Timing (normal sampling, FS is active)
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
23
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PARAMETER MEASUREMENT INFORMATION
VIH
CS
VIL
td(CSH-CSTARTL)
twL(CSTART)
VIH
CSTART
VIL
td(CSH-EOCH)
tt(I/O)
tt(I/O)
tconvert
VOH
EOC
VOL
td(CSTARTH-EOCL)
td(EOCH-INTL)
td(CSL-INTH)
VOH
INT
VOL
Figure 17. Critical Timing (extended sampling, single shot)
VIH
CS
twL(CSTART)
td(CSL-CSTARTL)
VIL
td(CSTARTH–CSTARTL)
VIH
90%
50%
10%
CSTART
td(CSH-EOCH)
tt(I/O)
VIL
tt(I/O)
VOH
EOC
VOL
td(CSTARTH-EOCL)
td(CSTARTH-INTL)
td(CSL-INTH)
INT
VOL
Figure 18. Critical Timing (extended sampling, repeat/sweep/repeat sweep)
24
VOH
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PARAMETER MEASUREMENT INFORMATION
tt(I/O)
tt(I/O)
VIH
CS
twH(CS)
tsu(CS-SCLK)
VIL
td(SCLK16F-CSH)
twL(SCLK)
tt(CLK)
twH(SCLK)
1
16
VIH
SCLK
VIL
tc(SCLK)
tsu(DI-CLK)
SDI
th(DI-CLK)
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ID15
td(CSL-DOV)
SDO
Hi-Z
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ
ID1
VIH
VIL
td(CLK-DOV)
OD15
OD1
VOH
Hi-Z
OD0
VOL
td(EOCH-DOZ)
td(CLK-EOCL)
VOH
ECO
VOL
td(SCLK-INTL)
td(CSL-INTH)
VOH
INT
VOL
Figure 19. Critical Timing (normal sampling, FS = 1)
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
25
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
TYPICAL CHARACTERISTICS
DIFFERENTIAL NONLINEARITY
vs
TEMPERATURE
INTEGRAL NONLINEARITY
vs
TEMPERATURE
0.5
0.53
VCC = 5 V,
Internal Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
DNL – Differential Nonlinearity – LSB
INL – Integral Nonlinearity – LSB
0.55
0.51
0.49
0.47
0.45
–40
25
TA – Temperature – °C
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
–40
85
Figure 20
0
1.7
1.6
1.5
1.4
1.3
1.2
–0.5
–1
–1.5
Gain Error – LSB
Offset Error – LSB
85
GAIN ERROR
vs
TEMPERATURE
1.1
1
0.9
0.8
VCC = 5 V,
External Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
25
TA – Temperature – °C
–2
–2.5
–3
–3.5
–4
–4.5
85
–5
–40
VCC = 5 V,
External Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
25
TA – Temperature – °C
Figure 22
26
25
TA – Temperature – °C
Figure 21
OFFSET ERROR
vs
TEMPERATURE
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–40
VCC = 5 V,
Internal Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
Figure 23
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
85
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
TYPICAL CHARACTERISTICS
POWER DOWN CURRENT
vs
TEMPERATURE
SUPPLY CURRENT
vs
TEMPERATURE
0.5
4
3.7
0.3
3.6
3.5
3.4
0.2
0
–0.1
–0.2
3.2
–0.3
3.1
–0.4
3
–40
25
TA – Temperature – °C
VCC = 5.5 V,
External Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
0.1
3.3
–0.5
–40
85
25
85
TA – Temperature – °C
Figure 24
Figure 25
INTEGRAL NONLINEARITY
vs
SAMPLES
INL – Integral Nonlinearity – LSB
Supply Current – mA
3.8
0.4
Power Down – µ A
3.9
VCC = 5.5 V,
External Reference = 4 V,
SCLK = 20 MHz,
Single Shot,
Short Sample,
Mode 00 µP mode
1.0
VCC = 5 V, External Reference = 5 V, SCLK = 20 MHz,
Single Shot, Short Sample, Mode 00 DSP Mode
0.8
0.6
0.4
0.2
–0.0
–0.2
–0.4
–0.6
–0.8
–1.0
0
2048
4096
Samples
Figure 26
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
27
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
DNL – Differential Nonlinearity – LSB
TYPICAL CHARACTERISTICS
DIFFERENTIAL NONLINEARITY
vs
SAMPLES
1.0
VCC = 5 V, External Reference = 5 V, SCLK = 20 MHz,
Single Shot, Short Sample, Mode 00 DSP Mode
0.8
0.6
0.4
0.2
–0.0
–0.2
–0.4
–0.6
–0.8
–1.0
0
2048
4096
Samples
Figure 27
INL – Integral Nonlinearity – LSB
INTEGRAL NONLINEARITY
vs
SAMPLES
1.0
VCC = 5 V, Internal Reference = 4 V, SCLK = 20 MHz,
Single Shot, Short Sample, Mode 00 DSP Mode
0.8
0.6
0.4
0.2
–0.0
–0.2
–0.4
–0.6
–0.8
–1.0
0
2048
Samples
Figure 28
28
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
4096
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
TYPICAL CHARACTERISTICS
DNL – Differential Nonlinearity – LSB
DIFFERENTIAL NONLINEARITY
vs
SAMPLES
1.0
VCC = 5 V, Internal Reference = 4 V, SCLK = 20 MHz,
Single Shot, Short Sample, Mode 00 DSP Mode
0.8
0.6
0.4
0.2
–0.0
–0.2
–0.4
–0.6
–0.8
–1.0
0
2048
4096
Samples
Figure 29
FAST POURIER TRANSFORM
vs
FREQUENCY
0
AIN = 50 kHz
VCC = 5 V, Channel 0
External Reference = 4 V
SCLK = 20 MHz
Single Shot, Short Sample
Mode 00 DSP Mode
Magnitude – dB
–20
–40
–60
–80
–100
–120
–140
0
50
100
150
200
f – Frequency – kHz
Figure 30
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
29
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
TYPICAL CHARACTERISTICS
EFFECTIVE NUMBER OF BITS
vs
INPUT FREQUENCY
SIGNAL-TO-NOISE + DISTORTION
vs
INPUT FREQUENCY
12.00
VCC = 5 V, External Reference = 4 V,
SCLK = 20 MHz, Single Shot, Short
Sample, Mode 00 DSP Mode
75
VCC = 5 V, External Reference = 4 V,
SCLK = 20 MHz, Single Shot,
Short Sample, Mode 00 DSP Mode
11.80
ENOB – Effective Number of Bits – BITS
SINAD – Signal-to-Noise + Distortion – dB
80
70
65
60
55
50
45
11.60
11.40
11.20
11.00
10.80
10.60
10.40
10.20
10.00
9.80
9.60
9.40
9.20
40
9.00
0
100
200
0
100
f – Frequency – kHz
f – Frequency – kHz
Figure 31
Figure 32
TOTAL HARMONIC DISTORTION
vs
INPUT FREQUENCY
SPURIOUS FREE DYNAMIC RANGE
vs
INPUT FREQUENCY
0
VCC = 5 V, External Reference = 4 V,
SCLK = 20 MHz, Single Shot,
Short Sample, Mode 00 DSP Mode
–55
Spurious Free Dynamic Range – dB
THD – Total Harmonic Distortion – dB
–50
–60
–65
–70
–75
–80
VCC = 5 V, External Reference = 4 V,
SCLK = 20 MHz, Single Shot,
Short Sample, Mode 00 DSP Mode
–20
–40
–60
–80
–100
0
25
50
75
100 125 150
f – Frequency – kHz
175
200
0
25
50
75
100
Figure 34
POST OFFICE BOX 655303
125
f – Frequency – kHz
Figure 33
30
200
• DALLAS, TEXAS 75265
150
175
200
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
4095
1111111111
VFS
See Notes A and B
1111111110
4094
1111111101
4093
VFT = VFS – 1/2 LSB
2049
1000000001
2048
1000000000
VZT =VZS + 1/2 LSB
Step
Digital Output Code
VFS Nom
2047
0111111111
VZS
0000000001
1
0000000000
0
0.0012
0.0024
2.4564
2.4576
2.4588
4.9134
2
0.0006
0000000010
4.9056
4.9104
0
4.9152
VI – Analog Input Voltage – V
NOTES: A. This curve is based on the assumption that Vref+ and Vref– have been adjusted so that the voltage at the transition from digital 0 to
1 (VZT) is 0.0006 V, and the transition to full scale (VFT) is 4.9134 V, 1 LSB = 1.2 mV.
B. The full scale value (VFS) is the step whose nominal midstep value has the highest absolute value. The zero-scale value (VZS) is
the step whose nominal midstep value equals zero.
Figure 35. Ideal 12-Bit ADC Conversion Characteristics
vcc
10 kΩ
VDD
XF
CS
TXD
SDI
RXD
SDO
AIN
CLKR
CLKX
TMS320 DSP
BIO
FSR
FSX
INT
SCLK
TLC2554/
TLC2558
FS
GND
Figure 36. Typical Interface to a TMS320 DSP
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
31
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
simplified analog input analysis
Using the equivalent circuit in Figure 39, the time required to charge the analog input capacitance from 0 to VS
within 1/2 LSB can be derived as follows.
ǒ ǒ ǓǓ
The capacitance charging voltage is given by:
Vc
+ Vs
1–EXP
–tc
Rt
(1)
Ci
Where
Rt = Rs + Zi
tc = Cycle time
ǒ Ǔ
ǒ Ǔ + ǒ ǒ ǓǓ
The input impedance Zi is 0.5 kΩ at 5 V. The final voltage to 1/2 LSB is given by:
ń
VC (1 2 LSB)
+ VS–
VS
8192
(2)
Equating equation 1 to equation 2 and solving for cycle time tc gives:
Vs–
VS
8192
Vs
1–EXP
–tc
Rt
(3)
Ci
and time to change to 1/2 LSB (minimum sampling time) is:
ń
tch (1 2 LSB)
Where
+ Rt
Ci
In(8192)
In(8192) = 9.011
Therefore, with the values given, the time for the analog input signal to settle is:
ń
tch (1 2 LSB)
+ (Rs ) 0.5 kW )
Ci
(4)
In(8192)
This time must be less than the converter sample time shown in the timing diagrams. This is 12× SCLKs (if the
sampling mode is short normal sampling mode).
ń
tch (1 2 LSB)
v 12
1
f (SCLK)
(5)
Therefore the maximum SCLK frequency is:
ƪ
max f ( SCLK )
32
ƫ + tch ǒ112ń2 LSBǓ + [In(8192)12 Rt
POST OFFICE BOX 655303
Ci ]
• DALLAS, TEXAS 75265
(6)
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
Driving Source†
TLC2554/58
Rs
VS
VI = Input Voltage at AIN
VS = External Driving Source Voltage
Rs = Source Resistance
ri = Input Resistance (MUX on Resistance)
Ci = Input Capacitance
VC = Capacitance Charging Voltage
ri
VI
VC
Ci
† Driving source requirements:
• Noise and distortion for the source must be equivalent to the resolution of the converter.
• Rs must be real at the input frequency.
Figure 37. Equivalent Input Circuit Including the Driving Source
maximum conversion throughput
For a supply voltage of 5 V, if the source impedance is less than 1 kΩ, and the ADC analog input capacitance
Ci is less than 50 pF, this equates to a minimum sampling time tch(0.5 LSB) of 0.676 µs. Since the sampling
time requires 12 SCLKs, the fastest SCLK frequency is 12/tch = 18 MHz.
The minimal total cycle time is given as:
tc
+ tcommand ) tch ) tconv ) td(EOCH–CSL ) + 4
+ 16 18 1MHz ) 1.7 ms + 2.59 ms
1
f (SCLK)
) 12
1
f (SCLK)
) 1.6 ms ) 0.1 ms
This is equivalent to a maximum throughput of 386 KSPS. The throughput can be even higher with a smaller
source impedance.
When source impedance is 100 Ω, the minimum sampling time becomes:
ń
tch (1 2 LSB)
+ Rt
Ci
In(8192)
+ 0.27 ms
The maximum SCLK frequency possible is 12/tch = 44 MHz. Then a 20 MHz clock (maximum SCLK frequency
for the TLC2554/2548 ) can be used. The minimal total cycle time is then reduced to:
tc
+ tcommand ) tch ) tconv ) td(EOCH–CSL ) + 4
+ 0.8 ms ) 1.6 ms ) 0.1 ms + 2.5 ms
1
f (SCLK)
) 12
1
f (SCLK)
) 1.6 ms ) 0.1 ms
The maximum throughput is 1/2.5 µs = 400 KSPS for this case.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
33
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
power down calculations
i(AVERAGE) = (fS /fSMAX ) × i(ON) + (1–fS /fSMAX ) × i(OFF)
CASE 1: If VDD = 3.3 V, auto power down, and an external reference is used:
+ 10 kHz
+ 200 kHz
f
SMAX
i (ON) +X 1 mA operating current and i (OFF) +X 1 mA auto power-down current
f
S
so
i (AVERAGE)
+ 0.05
1000 mA
) 0.95
1 mA
+ 51 mA
CASE 2: Now if software power down is used, another cycle is needed to shut it down.
+ 20 kHz
+ 200 kHz
f
SMAX
i (ON) +X 1 mA operating current and i (OFF) +X 1 mA power-down current
f
S
so
i (AVERAGE)
+ 0.1
1000 mA
) 0.9
1 mA
+ 101 mA
In reality this will be less since the second conversion never happened. It is only the additional cycle to shut down
the ADC.
34
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
CASE 3: Now if the hardware power down is used.
+ 10 kHz
+ 200 kHz
f
SMAX
i (ON) +X 1 mA operating current and i (OFF) +X 1 mA power-down current
f
S
so
i (AVERAGE)
+ 0.05
1000 mA
) 0.95
1 mA
+ 51 mA
difference between modes of conversion
The major difference between sweep mode (mode 10) and repeat sweep mode (mode 11) is that the sweep
sequence ends after the FIFO is filled up to the programmed threshold. The repeat sweep can either dump the
FIFO (by ignoring the FIFO content but simply reconfiguring the device) or read the FIFO and then repeat the
conversions on the the same sequence of the channel as before.
FIFO reads are expected after the FIFO is filled up to the threshold in each case. Mode 10 – the device allows
only FIFO read or CFR read or CFR write to be executed. Any conversion command is ignored. In the case of
mode 11, in addition to the above commands, conversion commands are also executed , i.e. the FIFO is cleared
and the sweep sequence is restarted.
Both single shot and repeat modes require selection of a channel after the device is configured for these modes.
Single shot mode does not use the FIFO, but repeat mode does. When the device is operating in repeat mode,
the FIFO can be dumped (by ignoring the FIFO content and simply reconfiguring the device) or the FIFO can
be read and then the conversions repeated on the same channel as before. However, the channel has to be
selected first before any conversion can be carried out. The devices can be programmed with the following
sequences for operating in the different modes that use a FIFO:
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
35
TLC2554, TLC2558
5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN
SLAS220A –JUNE 1999
PRINCIPLES OF OPERATION
difference between modes of conversion (continued)
REPEAT:
Configure FIFO Depth=4 /CONV Mode 01
Select Channel/
1st Conv (CS or CSTART)
2nd Conv (CS or CSTART)
3rd Conv (CS or CSTART)
4th Conv (CS or CSTART
FIFO READ 1
FIFO READ 2
FIFO READ 3
FIFO READ 4
Select Channel
1st Conv (CS or CSTART)
2nd Conv (CS or CSTART)
3rd Conv (CS or CSTART)
4th Conv (CS or CSTART
SWEEP:
Configure FIFO Depth=4 SEQ=1–2–3–4/CONV Mode 10
conv ch 1 (CS/CSTART)
conv ch 2 (CS/CSTART)
conv ch 3 (CS/CSTART)
conv ch 4 (CS/CSTART
FIFO READ ch 1 result
FIFO READ ch 2 result
FIFO READ ch 3 result
FIFO READ ch 4 result
Configure (not required if same sweep sequence is to be used again)
REPEAT SWEEP:
Configure FIFO Depth=4 SWEEP SEQ=1-2-3-4/CONV Mode 11
conv ch 1 (CS/CSTART)
conv ch 2 (CS/CSTART)
conv ch 3 (CS/CSTART)
conv ch 4 (CS/CSTART
FIFO READ ch 1 result
FIFO READ ch 2 result
FIFO READ ch 3 result
FIFO READ ch 4 result
conv ch 1 (CS/CSTART)
conv ch 2 (CS/CSTART)
conv ch 3 (CS/CSTART)
conv ch 4 (CS/CSTART
36
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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