TI1 ADS8556 12-bit, six-channel, simultaneous sampling analog-to-digital converter Datasheet

Sample &
Buy
Product
Folder
Support &
Community
Tools &
Software
Technical
Documents
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
ADS855x
16-, 14-, 12-Bit, Six-Channel, Simultaneous Sampling Analog-to-Digital Converters
1 Features
2 Applications
•
•
•
•
•
•
1
•
•
•
•
•
•
•
•
•
Family of 16-, 14-, 12-Bit, Pin- and
Software-Compatible ADCs
Six SAR ADCs Grouped in Three Pairs
Maximum Data Rate Per Channel with Internal
Conversion Clock and Reference:
ADS8556: 630 kSPS (PAR) or 450 kSPS (SER)
ADS8557: 670 kSPS (PAR) or 470 kSPS (SER)
ADS8558: 730 kSPS (PAR) or 500 kSPS (SER)
Maximum Data Rate with External Conversion
Clock and Reference:
800 kSPS (PAR) or 530 kSPS (SER)
Pin-Selectable or Programmable Input Voltage
Ranges: Up to ±12 V
Excellent Signal-to-Noise Performance:
ADS8556: 91.5 dB, ADS8667: 85 dB,
ADS8668: 73.9 dB
Programmable and Buffered Internal Reference:
0.5 V to 2.5 V and 0.5 V to 3.0 V
Comprehensive Power-Down Modes:
– Deep Power-Down (Standby Mode)
– Partial Power-Down
– Auto-Nap Power-Down
Selectable Parallel or Serial Interface
Operating Temperature Range: –40°C to 125°C
HVSS
AVDD
3 Description
The ADS855x contains six low-power, 16-, 14-, or 12bit, successive approximation register (SAR) based
analog-to-digital converters (ADCs) with true bipolar
inputs. Each channel contains a sample-and-hold
circuit that allows simultaneous high-speed multichannel signal acquisition.
The ADS855x supports data rates of up to 730 kSPS
in parallel interface mode or up to 500 kSPS if the
serial interface is used. The bus width of the parallel
interface can be set to eight or 16 bits. In serial
mode, up to three output channels can be activated.
The ADS855x is specified over the full industrial
temperature range of –40°C to 125°C and is available
in an LQFP-64 package.
Device Information(1)
PART NUMBER
ADS8557
SAR ADC
CH_B0
AGND
BUSY/INT
RANGE/XCLK
HW/SW
REFEN/WR
STBY
RESET
SAR ADC
CONVST_B
Config
Register
REFC_B
CH_B1
AGND
SAR ADC
CH_C0
AGND
SAR ADC
CONVST_C
CS/FS
RD
DB[15:0]
WORD/BYTE
PAR/SER
I/O
REFC_C
CH_C1
AGND
SAR ADC
String
DAC
REF_IO
AGND
10.00 mm × 10.00 mm
94
92
Signal-to-Noise Ratio (dB)
Control
Logic
REFC_A
CH_A1
AGND
LQFP (64)
SNR vs Temperature
SAR ADC
CONVST_A
BODY SIZE (NOM)
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
BVDD
Clock
Generator
CH_A0
AGND
PACKAGE
ADS8556
ADS8558
Block Diagram
HVDD
Power Quality Measurement
Protection Relays
Multi-Axis Motor Control
Programmable Logic Controllers
Industrial Data Acquisition
ADS8556
90
88
ADS8557
86
84
82
80
78
76
74
ADS8558
72
70
-40 -25 -10
5
20
35
50
65
80
95
110 125
Temperature (°C)
2.5V/3V
REF
BGND
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
7
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
Absolute Maximum Ratings ..................................... 7
ESD Ratings.............................................................. 7
Recommended Operating Conditions....................... 8
Thermal Information .................................................. 8
Electrical Characteristics: General ............................ 8
Electrical Characteristics: ADS8556 ....................... 11
Electrical Characteristics: ADS8557 ....................... 12
Electrical Characteristics: ADS8558 ....................... 13
Power Dissipation Characteristics .......................... 13
Serial Interface Timing Requirements .................. 14
Parallel Interface Timing Requirements (Read
Access) ................................................................... 14
6.12 Parallel Interface Timing Requirements (Write
Access) ................................................................... 15
6.13 Typical Characteristics .......................................... 17
7
7.1
7.2
7.3
7.4
7.5
8
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
Register Maps .........................................................
23
23
24
28
32
Application and Implementation ........................ 35
8.1 Application Information............................................ 35
8.2 Typical Application .................................................. 35
9 Power Supply Recommendations...................... 39
10 Layout................................................................... 39
10.1 Layout Guidelines ................................................. 39
10.2 Layout Example .................................................... 40
11 Device and Documentation Support ................. 41
11.1
11.2
11.3
11.4
11.5
11.6
Documentation Support .......................................
Related Links ........................................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
41
41
41
41
41
41
12 Mechanical, Packaging, and Orderable
Information ........................................................... 41
Detailed Description ............................................ 23
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (November 2015) to Revision D
Page
•
Moved Electrical Characteristics: General table to before other Electrical Characteristics tables ......................................... 8
•
Added text reference for Figure 42 ...................................................................................................................................... 32
•
Changed Figure 43: changed capacitor values from 820 nF to 820 pF............................................................................... 36
Changes from Revision B (January 2012) to Revision C
•
Page
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1
Changes from Revision A (August 2009) to Revision B
Page
•
Changed unit column for all tCONV rows in the Serial Interface Timing Requirements table................................................. 14
•
Added tS3 row to Serial Interface Timing Requirements table.............................................................................................. 14
•
Changed unit column for all tCONV rows in Parallel Interface Timing Requirements (Read Access) table ........................... 14
•
Updated Figure 2.................................................................................................................................................................. 15
•
Updated Figure 3.................................................................................................................................................................. 16
•
Changed second paragraph of CONVST_x section............................................................................................................. 25
•
Changed minimum bandwidth value in last sentence of Reference section ........................................................................ 26
•
Updated Figure 38................................................................................................................................................................ 29
2
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
5 Pin Configuration and Functions
56
AGND
57
AVDD
58
REFIO
59
AGND
REFC_C
60
AGND
AGND
61
AGND
AVDD
62
REFC_A
PAR/SER
63
AGND
HW/SW
64
REFC_B
DB15
REFEN/WR
PM Package
64-Pin LQFP
Top View
55
54
53
52
51
50
49
DB14/REFBUFEN
1
48 CH_C1
DB13/SDI
2
47 AVDD
DB12
3
46 AVDD
DB11
4
45 CH_C0
DB10/SDO_C
5
44 AGND
DB9/SDO_B
6
43 AGND
DB8/SDO_A
7
BGND
8
BVDD
9
42 CH_B1
ADS8556
ADS8557
ADS8558
41 AVDD
40 AVDD
DB7/HBEN/DCEN 10
39 CH_B0
20
21
22
23
24
25
26
27
28
29
30
31
32
HVDD
AGND
19
HVSS
18
WORD/BYTE
17
RESET
33 CH_A0
RANGE/XCLK
DB1/SEL_B 16
AVDD
34 AVDD
AGND
DB2/SEL_C 15
STBY
35 AVDD
CONVST_A
DB3/DCIN_C 14
CONVST_B
36 CH_A1
RD
DB4/DCIN_B 13
CONVST_C
37 AGND
CS/FS
DB5/DCIN_A 12
BUSY/INT
38 AGND
DB0/SEL_A
DB6/SCLK 11
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
3
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Pin Functions
PIN
NAME
NO.
DB14/REFBUFEN
1
TYPE (1)
DIO, DI
DESCRIPTION
PARALLEL INTERFACE (PAR/SER = 0)
SERIAL INTERFACE (PAR/SER = 1)
Hardware mode (HW/SW = 0):
Reference buffers enable input.
When low, all reference buffers are enabled
(mandatory if internal reference is used). When
high, all reference buffers are disabled.
Data bit 14 input/output
Output is '0' for the ADS8557, ADS8558
Software mode (HW/SW = 1):
Connect to BGND or BVDD.
The reference buffers are controlled by bit C24
(REFBUF) in control register (CR).
Hardware mode (HW/SW = 0):
Connect to BGND
Data bit 13 input/output
Output is MSB for the ADS8557
and '0' for the ADS8558
DB13/SDI
2
DIO, DI
DB12
3
DIO
Data bit 12 input/output
Output is '0' for the ADS8558
Connect to BGND
DB11
4
DIO
Data bit 11 input/output
Output is MSB for the ADS8558
Connect to BGND
DB10/SDO_C
5
DIO, DO Data bit 10 input/output
When SEL_C = 1, data output for channel C
When SEL_C = 0, tie this pin to BGND
DB9/SDO_B
6
DIO, DO Data bit 9 input/output
When SEL_B = 1, data output for channel B
When SEL_B = 0, tie this pin to BGND
When SEL_C = 0, data from channel C1 are
also available on this output
DIO, DO Data bit 8 input/output
Data output for channel A
When SEL_C = 0, data from channel C0 are
also available on this output
When SEL_C = 0 and SEL_B = 0, SDO_A acts
as the single data output for all channels
Software mode (HW/SW = 1):
Serial data input
DB8/SDO_A
7
BGND
8
P
Buffer IO ground, connect to digital ground plane
BVDD
9
P
Buffer IO supply, connect to digital supply (2.7 V to 5.5 V). Decouple with a 1-μF ceramic
capacitor or a combination of 100-nF and 10-μF ceramic capacitors to BGND.
Word mode (WORD/BYTE = 0): Data bit 7
input/output
DB7/HBEN/DCEN
DB6/SCLK
DB5/DCIN_A
DB4/DCIN_B
DB3/DCIN_C
(1)
4
10
11
12
13
14
DIO, DI,
DI
DIO, DI
DIO, DI
DIO, DI
DIO, DI
Byte mode (WORD/BYTE = 1):
High byte enable input.
When high, the high byte is output first on
DB[15:8]. When low, the low byte is output first
on DB[15:8].
Word mode (WORD/BYTE = 0):
Data bit 6 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 5 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 4 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 3 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Daisy-chain enable input.
When high, DB[5:3] serve as daisy-chain inputs
DCIN[A:C]. If daisy-chain mode is not used,
connect to BGND.
Serial interface clock input (36 MHz, max)
When DCEN = 1, daisy-chain data input for
channel A.
When DCEN = 0, connect to BGND.
When SEL_B = 1 and DCEN = 1,
daisy-chain data input for channel B.
When DCEN = 0, connect to BGND.
When SEL_C = 1 and DCEN = 1,
daisy-chain data input for channel C.
When DCEN = 0, connect to BGND.
AI = analog input; AIO = analog input/output; DI = digital input; DO = digital output; DIO = digital input/output; and P = power supply.
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Pin Functions (continued)
PIN
NAME
DB2/SEL_C
DB1/SEL_B
DB0/SEL_A
NO.
15
16
17
TYPE (1)
DIO, DI
DIO, DI
DIO, DI
BUSY/INT
18
DO
CS/FS
19
DI, DI
RD
20
DI
CONVST_C
21
DI
DESCRIPTION
PARALLEL INTERFACE (PAR/SER = 0)
Word mode (WORD/BYTE = 0):
Data bit 2 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 1 input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
Word mode (WORD/BYTE = 0):
Data bit 0 (LSB) input/output
Byte mode (WORD/BYTE = 1):
Connect to BGND or BVDD
SERIAL INTERFACE (PAR/SER = 1)
Select SDO_C input.
When high, SDO_C is active. When low,
SDO_C is disabled.
Select SDO_B input.
When high, SDO_B is active. When low,
SDO_B is disabled.
Select SDO_A input.
When high, SDO_A is active. When low,
SDO_A is disabled. Must always be high.
When CR bit C21 = 0 (BUSY/INT), converter busy status output. Transitions high when a
conversion has been started and remains high during the entire process. Transitions low when
the conversion data of all six channels are latched to the output register and remains low
thereafter.
In sequential mode (SEQ = 1 in the CR), the BUSY output transitions high when a conversion
has been started and goes low for a single conversion clock cycle (tCCLK) whenever a channel
pair conversion is completed.
When bit C21 = 1 (BUSY/INT in CR), interrupt output. This bit transitions high after a conversion
completes and remains high until the conversion result is read.
The polarity of BUSY/INT output can be changed using bit C20 (BUSY L/H) in the control
register.
Chip select input.
When low, the parallel interface is enabled.
When high, the interface is disabled.
Frame synchronization.
The falling edge of FS controls the frame
transfer.
Read data input.
When low, the parallel data output is enabled.
When high, the data output is disabled.
Connect to BGND.
Hardware mode (HW/SW = 0): Conversion start of channel pair C.
The rising edge of this signal initiates simultaneous conversion of analog signals at inputs
CH_C[1:0]. CONVST_C must remain high during the entire conversion cycle, otherwise both
ADCs of channel C are put in partial power-down mode (see the Reset and Power-Down Modes
section).
Software mode (HW/SW = 1): Conversion start of channel pair C in sequential mode (CR bit C23
= 1) only; connect to BGND or BVDD otherwise.
CONVST_B
22
DI
Hardware mode (HW/SW = 0): Conversion start of channel pair B.
The rising edge of this signal initiates simultaneous conversion of analog signals at inputs
CH_B[1:0]. CONVST_B must remain high during the entire conversion cycle; otherwise, both
ADCs of channel B are put into partial power-down mode (see the Reset and Power-Down
Modes section).
Software mode (HW/SW = 1): Conversion start of channel pair B in sequential mode (CR bit C23
= 1) only; connect to BGND or BVDD otherwise.
CONVST_A
23
DI
Hardware mode (HW/SW = 0): Conversion start of channel pair A.
The rising edge of this signal initiates simultaneous conversion of analog signals at inputs
CH_A[1:0]. CONVST_A must remain high during the entire conversion cycle; otherwise, both
ADCs of channel A are put into partial power-down mode (see the Reset and Power-Down
Modes section).
Software mode (HW/SW = 1): Conversion start of all selected channels except in sequential
mode
(CR bit C23 = 1): Conversion start of channel pair A only.
STBY
24
DI
Standby mode input. When low, the entire device is powered-down (including the internal clock
and reference).
When high, the device operates in normal mode.
AGND
25, 32,
37, 38,
43, 44,
49, 52,
53, 55,
57, 59
P
Analog ground, connect to analog ground plane
Pin 25 can have a dedicated ground if the difference between its potential and AGND is always
kept within ±300 mV.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
5
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Pin Functions (continued)
PIN
NAME
NO.
AVDD
26, 34,
35, 40,
41, 46,
47, 50,
60
TYPE (1)
P
DESCRIPTION
PARALLEL INTERFACE (PAR/SER = 0)
SERIAL INTERFACE (PAR/SER = 1)
Analog power supply (4.5 V to 5.5 V). Decouple each pin with a 100-nF ceramic capacitor to
AGND. Use an additional 10-μF capacitor to AGND close to the device but without compromising
the placement of the smaller capacitor. Pin 26 can have a dedicated power supply if the
difference between its potential and AVDD is always kept within ±300 mV.
Hardware mode (HW/SW = 0): Input voltage range select input.
When low, the analog input range is ±4 VREF. When high, the analog input range is ±2 VREF.
RANGE/XCLK
27
DI, DIO
RESET
28
DI
Reset input, active high. Aborts any ongoing conversions. Resets the internal control register to
0x000003FF. The RESET pulse must be at least 50 ns long.
Software mode (HW/SW = 1): External conversion clock input, if CR bit C11 (CLKSEL) is set
high or internal conversion clock output, if CR bit C10 (CLKOUT_EN) is set high. If not used,
connect to BVDD or BGND.
WORD/BYTE
29
DI
Output mode selection input.
When low, data are transferred in word mode
using DB[15:0]. When high, data are
transferred in byte mode using DB[15:8] with
the byte order controlled by HBEN pin while two
accesses are required for a complete 16-bit
transfer.
HVSS
30
P
Negative supply voltage for the analog inputs (–16.5 V to –5 V).
Decouple with a 100-nF ceramic capacitor to AGND placed next to the device and a 10-μF
capacitor to AGND close to the device but without compromising the placement of the smaller
capacitor.
HVDD
31
P
Positive supply voltage for the analog inputs (5 V to 16.5 V). Decouple with a 100-nF ceramic
capacitor to AGND placed next to the device and a 10-μF capacitor to AGND close to the device
but without compromising the placement of the smaller capacitor.
CH_A0
33
AI
Analog input of channel A0. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C26 (RANGE_A) in software mode.
CH_A1
36
AI
Analog input of channel A1. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C26 (RANGE_A) in software mode.
CH_B0
39
AI
Analog input of channel B0. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C27 (RANGE_B) in software mode.
CH_B1
42
AI
Analog input of channel B1. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C27 (RANGE_B) in software mode.
CH_C0
45
AI
Analog input of channel C0. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C28 (RANGE_C) in software mode.
CH_C1
48
AI
Analog input of channel C1. The input voltage range is controlled by RANGE pin in hardware
mode or CR bit C28 (RANGE_C) in software mode.
REFIO
51
AIO
REFC_A
54
AI
Decoupling capacitor for reference of channels A.
Connect a 10-μF ceramic decoupling capacitor between this pin and pin 53.
REFC_B
56
AI
Decoupling capacitor for reference of channels B.
Connect a 10-μF ceramic decoupling capacitor between this pin and pin 55.
REFC_C
58
AI
Decoupling capacitor for reference of channels C.
Connect a 10-μF ceramic decoupling capacitor between this pin and pin 57.
PAR/SER
61
DI
Interface mode selection input.
When low, the parallel interface is selected. When high, the serial interface is enabled.
DI
Mode selection input.
When low, the hardware mode is selected and part works according to the settings of external
pins. When high, the software mode is selected in which the device is configured by writing into
the control register.
HW/SW
6
62
Submit Documentation Feedback
Connect to BGND.
Reference voltage input/output (0.5 V to 3.025 V).
The internal reference is enabled via REFEN/WR pin in hardware mode or CR bit C25 (REFEN) in
software mode. The output value is controlled by the internal DAC (CR bits C[9:0]). Connect a
470-nF ceramic decoupling capacitor between this pin and pin 52.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Pin Functions (continued)
PIN
NAME
NO.
REFEN/WR
63
DB15
DESCRIPTION
TYPE (1)
64
DI
DIO
PARALLEL INTERFACE (PAR/SER = 0)
SERIAL INTERFACE (PAR/SER = 1)
Hardware mode (HW/SW = 0):
Internal reference enable input.
When high, the internal reference is enabled
(the reference buffers are to be enabled). When
low, the internal reference is disabled and an
external reference is applied at REFIO.
Hardware mode (HW/SW = 0):
Internal reference enable input.
When high, the internal reference is enabled
(the reference buffers are to be enabled). When
low, the internal reference is disabled and an
external reference must be applied at REFIO.
Software mode (HW/SW = 1): Write input.
The parallel data input is enabled, when CS
and WR are low. The internal reference is
enabled by the CR bit C25 (REFEN).
Software mode (HW/SW = 1): Connect to
BGND or BVDD.
The internal reference is enabled by CR bit C25
(REFEN).
Data bit 15 (MSB) input/output.
Output is '0' for the ADS8557/8.
Connect to BGND.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
–0.3
18
V
Supply voltage, HVSS to AGND
–18
0.3
V
Supply voltage, AVDD to AGND
–0.3
6
V
Supply voltage, BVDD to BGND
–0.3
6
V
Analog input voltage
HVSS – 0.3
HVDD + 0.3
V
Reference input voltage with respect to AGND
AGND – 0.3
AVDD + 0.3
V
Digital input voltage with respect to BGND
BGND – 0.3
BVDD + 0.3
V
Supply voltage, HVDD to AGND
Ground voltage difference AGND to BGND
Input current to all pins except supply
–10
Maximum virtual junction temperature, TJ
Storage Temperature, Tstg
(1)
-65
±0.3
V
10
mA
150
°C
150
°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.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001
JEDEC standard 22, test method A114-C.01 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101
JEDEC standard 22, test method C101 (2)
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
7
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
6.3 Recommended Operating Conditions
MIN
NOM
MAX
4.5
5
5.5
Low-voltage levels
2.7
3.0
3.6
5-V logic levels
4.5
5
5.5
Supply voltage, AVDD to AGND
Supply voltage, BVDD to BGND
Input supply voltage, HVDD to AGND
Input supply voltage, HVSS to AGND
Range 1 (±2 × VREF)
2 × VREF
16.5
Range 2 (±4 × VREF)
4 × VREF
16.5
Range 1 (±2 × VREF)
–16.5
–2 × VREF
Range 2 (±4 × VREF)
–16.5
–4 × VREF
Range 1 (±2 × VREF)
–2 × VREF
2 × VREF
Range 1 (±4 × VREF)
–4 × VREF
4 × VREF
–40
125
Reference input voltage (VREF)
Analog inputs (1)
0.5
Operating ambient temperature, TA
(1)
2.5
UNIT
V
V
V
V
3.0
V
V
°C
For more information, see the Analog Inputs section.
6.4 Thermal Information
ADS855x
THERMAL METRIC (1)
PM (LQFP)
UNIT
64 PINS
High-K thermal resistance (2)
RθJA
Junction-to-ambient thermal resistance
50.3
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
12.0
°C/W
RθJB
Junction-to-board thermal resistance
24.0
°C/W
ψJT
Junction-to-top characterization parameter
0.5
°C/W
ψJB
Junction-to-board characterization parameter
23.5
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
NA
°C/W
(1)
(2)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
Modeled in accordance with the Low-K or High-K thermal metric definitions of EIA/JESD51-3.
6.5 Electrical Characteristics: General
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5.5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
ANALOG INPUT
CHXX
Bipolar full-scale range
Input capacitance
Input leakage current
RANGE pin/RANGE bit = 0
–4 × VREF
4 × VREF
RANGE pin/RANGE bit = 1
–2 × VREF
2 × VREF
Input range = ±4 × VREF
10
Input range = ±2 × VREF
20
No ongoing conversion
Aperture delay matching
pF
±1
Aperture delay
Common CONVST for all channels
Aperture jitter
V
μA
5
ns
250
ps
50
ps
EXTERNAL CLOCK INPUT (XCLK)
fXCLK
External clock frequency
An external reference must be used for fXCLK > fCCLK
1
External clock duty cycle
(1)
8
45%
18
20
MHz
55%
All values are at TA = 25°C.
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Electrical Characteristics: General (continued)
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5.5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
MIN
TYP (1)
MAX
2.5-V operation, REFDAC = 0x3FF
2.485
2.5
2.515
2.5-V operation, REFDAC = 0x3FF at 25°C
2.496
2.5
2.504
3-V operation, REFDAC = 0x3FF
2.985
3.0
3.015
3-V operation, REFDAC = 0x3FF at 25°C
2.995
3.0
3.005
PARAMETER
TEST CONDITIONS
UNIT
REFERENCE VOLTAGE OUTPUT (REFOUT)
VREF
Reference voltage
dVREF/dT
Reference voltage drift
PSRR
Power-supply rejection ratio
IREFOUT
Output current
IREFSC
Short-circuit current (2)
50
mA
tREFON
Turn-on settling time
10
ms
External load capacitance
REFDAC
Tuning range
±10
V
ppm/°C
73
With dc current
2
At CREF_x pins
4.7
10
At REFIO pins
100
470
Internal reference output voltage range
dB
–2
μF
0.2 × VREF
REFDAC resolution
10
DNLDAC
REFDAC differential nonlinearity
–1
INLDAC
REFDAC integral nonlinearity
VOSDAC
REFDAC offset error
VREF = 0.5 V (DAC = 0x0CC)
mA
VREF
V
Bits
±0.1
1
LSB
–2
±0.1
2
LSB
–4
±0.65
4
LSB
2.5
3.025
REFERENCE VOLTAGE INPUT (REFIN)
VREFIN
Reference input voltage
0.5
Input resistance
100
Input capacitance
V
MΩ
5
pF
Reference input current
1
μA
SERIAL CLOCK INPUT (SCLK)
fSCLK
Serial clock input frequency
tSCLK
Serial clock period
Serial clock duty cycle
0.1
36
MHz
0.0278
10
μs
40%
60%
DIGITAL INPUTS (3)
Logic family
CMOS with Schmitt-Trigger
High-level input voltage
0.7 × BVDD
BVDD + 0.3
Low-level input voltage
BGND – 0.3
0.3 × BVDD
V
–50
50
nA
Input current
VI = BVDD to BGND
Input capacitance
5
V
pF
DIGITAL OUTPUTS (3)
Logic family
CMOS
High-level output voltage
IOH = 100 μA
Low-level output voltage
IOH = –100 μA
BVDD – 0.6
BVDD
V
BGND
BGND + 0.4
V
–50
50
nA
High-impedance-state output
current
Output capacitance
5
Load capacitance
(2)
(3)
pF
30
pF
Reference output current is not limited internally.
Specified by design.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
9
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Electrical Characteristics: General (continued)
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5.5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
POWER-SUPPLY REQUIREMENTS
AVDD
Analog supply voltage
4.5
5
5.5
V
BVDD
Buffer I/O supply voltage
2.7
3
5.5
V
HVDD
Input positive supply voltage
5
10
16.5
V
HVSS
Input negative supply voltage
–16.5
–10
–5
V
fDATA = maximum
30
36
ADS8556, fDATA = 250 kSPS (auto-NAP mode)
14
16.5
ADS8557, fDATA = 250 kSPS (auto-NAP mode)
14
17
ADS8558, fDATA = 250 kSPS (auto-NAP mode)
14
18
4
6
Power-down mode
0.1
50
fDATA = maximum
0.9
2
fDATA = 250 kSPS (auto-NAP mode)
0.5
1.5
Auto-NAP mode, no ongoing conversion, internal
conversion clock
0.1
10
Power-down mode
0.1
10
ADS8556, fDATA = maximum
3
3.5
ADS8557, fDATA = maximum
3.1
3.6
ADS8558, fDATA = maximum
3.3
4
fDATA = 250 kSPS (auto-NAP mode)
1.6
2
Auto-NAP mode, no ongoing conversion, internal
conversion clock
0.2
0.3
Power-down mode
0.1
10
ADS8556, fDATA = maximum
3.6
4
ADS8557, fDATA = maximum
3.6
4.2
ADS8558, fDATA = maximum
4
4.8
fDATA = 250 kSPS (auto-NAP mode)
1.8
2.2
Auto-NAP mode, no ongoing conversion, internal
conversion clock
0.2
0.25
Power-down mode
0.1
10
ADS8556, fDATA = maximum
251.7
298.5
ADS8557, fDATA = maximum
253.2
303
ADS8558, fDATA = maximum
262.2
318
ADS8556, fDATA = 250 kSPS (auto-NAP mode)
122.5
150
ADS8557, fDATA = 250 kSPS (auto-NAP mode)
122.5
152.5
ADS8558, fDATA = 250 kSPS (auto-NAP mode)
122.5
157.5
Auto-NAP mode, no ongoing conversion, internal
conversion clock
26
38.3
Power-down mode
3.8
580
IAVDD
Analog supply current (4)
Auto-NAP mode, no ongoing conversion, internal
conversion clock
IBVDD
IHVDD
IHVSS
Buffer I/O supply current
(5)
Input positive supply current (6)
Input negative supply current (7)
Power dissipation (8)
(4)
(5)
(6)
(7)
(8)
10
mA
μA
mA
μA
mA
μA
mA
μA
mW
μW
At AVDD = 5 V.
At BVDD = 3 V, parallel mode, load capacitance = 6 pF per pin.
At HVDD = 15 V.
At HVSS = –15 V.
At AVDD = 5 V, BVDD = 3 V, HVDD = 15 V, and HVSS = –15 V.
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
6.6 Electrical Characteristics: ADS8556
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = 630 kSPS in parallel mode or 450 kSPS in
serial mode (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
DC ACCURACY
Resolution
16
No missing codes
INL
Integral linearity error
DNL
Differential linearity error
Bits
At TA = –40°C to 85°C
–3
±1.5
3
At TA = –40°C to 125°C
–4
±1.5
4
At TA = –40°C to 85°C
–1
±0.75
1.5
At TA = –40°C to 125°C
–1
±0.75
2
–4
±0.8
4
Offset error
Offset error drift
PSRR
Bits
16
LSB
LSB
mV
μV/°C
±3.5
Gain error
Referenced to voltage at REFIO
Gain error drift
Referenced to voltage at REFIO
–0.75
±0.25
±6
0.75
ppm/°C
%FSR
Power-supply rejection ratio
At output code FFFFh, related to AVDD
60
dB
SAMPLING DYNAMICS
tACQ
Acquisition time
tCONV
Conversion time per ADC
tCCLK
Internal conversion clock period
fDATA
Throughput rate
280
ns
1.26
μs
18.5
tCCLK
68.0
ns
Parallel interface, internal clock and reference
630
Serial interface, internal clock and reference
450
kSPS
AC ACCURACY
SNR
Signal-to-noise ratio
SINAD
Signal-to-noise ratio + distortion
THD
Total harmonic distortion (2)
SFDR
Spurious-free dynamic range
Channel-to-channel isolation
–3-dB small-signal bandwidth
(1)
(2)
At fIN = 10 kHz, TA = –40°C to 85°C
90
91.5
At fIN = 10 kHz, TA = –40°C to 125°C
89
91.5
87
89.5
86.5
89.5
At fIN = 10 kHz, TA = –40°C to 85°C
At fIN = 10 kHz, TA = –40°C to 125°C
dB
dB
At fIN = 10 kHz, TA = –40°C to 85°C
–94
–90
At fIN = 10 kHz, TA = –40°C to 125°C
–94
–89.5
At fIN = 10 kHz, TA = –40°C to 85°C
At fIN = 10 kHz, TA = –40°C to 125°C
At fIN = 10 kHz
90
95
89.5
95
100
In 4 × VREF mode
48
In 2 × VREF mode
24
dB
dB
dB
MHz
All values are at TA = 25°C.
Calculated on the first nine harmonics of the input frequency.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
11
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
6.7 Electrical Characteristics: ADS8557
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5.5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = 670 kSPS in parallel mode or 470 kSPS in
serial mode (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
DC ACCURACY
Resolution
14
Bits
No missing codes
14
INL
Integral linearity error
–1
±0.4
1
LSB
DNL
Differential linearity error
–1
±0.25
1
LSB
Offset error
–4
±0.8
4
Offset error drift
PSRR
Bits
–0.75
±0.25
mV
μV/°C
±3.5
Gain error
Referenced to voltage at REFIO
Gain error drift
Referenced to voltage at REFIO
±6
0.75
ppm/°C
%FSR
Power-supply rejection ratio
At output code FFFFh, related to AVDD
60
dB
SAMPLING DYNAMICS
tACQ
Acquisition time
tCONV
Conversion time per ADC
tCCLK
Internal conversion clock period
fDATA
280
Throughput rate
ns
1.19
μs
18.5
tCCLK
64.1
ns
Parallel interface, internal clock and reference
670
Serial interface, internal clock and reference
470
kSPS
AC ACCURACY
SNR
Signal-to-noise ratio
At fIN = 10 kHz
84
85
dB
SINAD
Signal-to-noise ratio + distortion
At fIN = 10 kHz
83
84
dB
(2)
THD
Total harmonic distortion
SFDR
Spurious-free dynamic range
At fIN = 10 kHz
Channel-to-channel isolation
At fIN = 10 kHz
–3-dB small-signal bandwidth
(1)
(2)
12
At fIN = 10 kHz
–91
86
–86
dB
92
dB
100
dB
In 4 × VREF mode
48
In 2 × VREF mode
24
MHz
All values are at TA = 25°C.
Calculated on the first nine harmonics of the input frequency.
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
6.8 Electrical Characteristics: ADS8558
over recommended operating free-air temperature range of –40°C to 125°C, AVDD = 4.5 V to 5 V, BVDD = 2.7 V to 5.5 V,
HVDD = 10 V to 15 V, HVSS = –15 V to –10 V, VREF = 2.5 V (internal), and fDATA = 730 kSPS in parallel mode or 500 kSPS in
serial mode (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP (1)
MAX
UNIT
DC ACCURACY
Resolution
12
No missing codes
INL
Integral linearity error
DNL
Differential linearity error
Offset error
Bits
–0.75
±0.2
0.75
LSB
–0.5
±0.2
0.5
LSB
–4
±0.8
4
Offset error drift
PSRR
Bits
12
mV
μV/°C
±3.5
Gain error
Referenced to voltage at REFIO
Gain error drift
Referenced to voltage at REFIO
–0.75
±0.25
±6
0.75
ppm/°C
%FSR
Power-supply rejection ratio
At output code FFFFh, related to AVDD
60
dB
SAMPLING DYNAMICS
tACQ
Acquisition time
tCONV
Conversion time per ADC
tCCLK
Internal conversion clock period
fDATA
280
Throughput rate
ns
1.09
μs
18.5
tCCLK
58.8
ns
Parallel interface, internal clock and reference
730
Serial interface, internal clock and reference
500
kSPS
AC ACCURACY
SNR
Signal-to-noise ratio
At fIN = 10kHz
73
73.9
dB
SINAD
Signal-to-noise ratio + distortion
At fIN = 10kHz
73
73.8
dB
(2)
THD
Total harmonic distortion
SFDR
Spurious-free dynamic range
At fIN = 10kHz
Channel-to-channel isolation
At fIN = 10kHz
–3-dB small-signal bandwidth
(1)
(2)
At fIN = 10kHz
–89
84
–84
dB
92
dB
100
dB
In 4 × VREF mode
48
In 2 × VREF mode
24
MHz
All values are at TA = 25°C.
Calculated on the first nine harmonics of the input frequency.
6.9 Power Dissipation Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
PD
Device power
dissipation
TYP
MAX
ADS8556, HVDD = 15 V, HVSS = –15 V, AVDD = 5 V,
BVDD = 3 V, and fDATA = maximum
TEST CONDITIONS
251.7
298.5
ADS8557, HVDD = 15 V, HVSS = –15 V, AVDD = 5 V,
BVDD = 3 V, and fDATA = maximum
253.2
303.0
ADS8558, HVDD = 15 V, HVSS = –15 V, AVDD = 5 V,
BVDD = 3 V, and fDATA = maximum
262.2
318.0
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
MIN
Submit Documentation Feedback
UNIT
mW
13
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
6.10 Serial Interface Timing Requirements
over recommended operating free-air temperature range at –40°C to 125°C, AVDD = 5 V, and BVDD = 2.7 V to 5.5 V (unless
otherwise noted) (1)
MIN
tACQ
Acquisition time
tCONV
Conversion time
t1
CONVST_x low time
t2
BUSY low to FS low time
NOM
MAX
280
UNIT
ns
ADS8556
1.26
ADS8557
1.19
ADS8558
1.09
µs
20
ns
0
ns
ADS8556
40
ADS8557
20
ADS8558
0
t3
Bus access finished to next conversion start
time
tD1
CONVST_x high to BUSY high delay
5
20
ns
tD2
FS low to SDO_x active delay
5
12
ns
tD3
SCLK rising edge to new data valid delay
15
ns
tD4
FS high to SDO_x 3-state delay
10
ns
tH1
Input data to SCLK falling edge hold time
5
ns
tH2
Output data to SCLK rising edge hold time
5
ns
tS1
Input data to SCLK falling edge setup time
3
ns
tS3
CONVST_x high to XCLK falling or rising edge setup time
6
tSCLK
Serial clock period
(1)
ns
ns
0.0278
10
μs
All input signals are specified with tR = tF = 1.5 ns (10% to 90% of BVDD) and timed from a voltage level of (VIL + VIH) / 2.
6.11 Parallel Interface Timing Requirements (Read Access)
over recommended operating free-air temperature range at –40°C to 125°C, AVDD = 5 V, and BVDD = 2.7 V to 5.5 V (unless
otherwise noted) (1)
MIN
tACQ
Acquisition time
tCONV
Conversion time
t1
CONVST_x low time
t2
BUSY low to CS low time
NOM
MAX
280
UNIT
ns
ADS8556
1.26
ADS8557
1.19
ADS8558
1.09
µs
20
ns
0
ns
ADS8556
40
ADS8557
20
ADS8558
0
t3
Bus access finished to next conversion start
time (2)
t4
CS low to RD low time
0
ns
t5
RD high to CS high time
0
ns
t6
RD pulse duration
30
ns
t7
Minimum time between two read accesses
10
tD1
CONVST_x high to BUSY high delay
tD5
RD falling edge to output data valid delay
tH3
Output data to RD rising edge hold time
(1)
(2)
14
5
ns
ns
20
ns
20
ns
5
ns
All input signals are specified with tR = tF = 1.5 ns (10% to 90% of BVDD) and timed from a voltage level of (VIL + VIH) / 2.
Refer to the CS signal or RD, whichever occurs first.
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
6.12 Parallel Interface Timing Requirements (Write Access)
over recommended operating free-air temperature range at –40°C to 125°C, AVDD = 5 V, and BVDD = 2.7 V to 5.5 V (unless
otherwise noted) (1)
MIN
NOM
MAX
UNIT
t8
CS low to WR low time
0
ns
t9
WR low pulse duration
15
ns
t10
WR high pulse duration
10
ns
t11
WR high to CS high time
0
ns
tS2
Output data to WR rising edge setup time
5
ns
tH4
Data output to WR rising edge hold time
5
ns
(1)
All input signals are specified with tR = tF = 1.5 ns (10% to 90% of BVDD) and timed from a voltage level of (VIL + VIH) / 2.
Input range: ±2VREF
Input range: ±4VREF
RSER = 200W
RSW = 130W
RSER = 200W
CH_XX
RSW = 130W
CH_XX
CS = 20pF
CS = 10pF
VDC
CPAR = 5pF
VDC
CPAR = 5pF
CS = 20pF
CS = 10pF
AGND
AGND
RSER = 200W
RSW = 130W
RSER = 200W
RSW = 130W
Figure 1. Equivalent Input Circuits
XCLK
(C11 = 1)
tS3
tS3
t1
CONVST_x
tACQ
tCONV
tD1
BUSY
(C20 = C21 = 0)
t3
t2
FS
tSCLK
32
1
SCLK
tD4
tD3
tD2
ADS8556
SDO_x
CH_x0
MSB
tH2
CH_x1
D3
tS1
SDI or
DCIN_x
Don’t Care
D31
D3
CH_x1
D2
tH1
CH_x1
D1
CH_x1
LSB
D2
D1
D0
Don’t
Care
Figure 2. Serial Operation Timing Diagram (All Three SDOs Active)
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
15
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
t1
CONVST_A
CONVST_B
CONVST_C
tCONV
tACQ
tD1
BUSY
(C20 = C21 = 0)
t3
t2
CS
t4
t6
t5
t7
RD
tD5
CH
A0
DB[15:0]
CH
A1
CH
B0
tH3
CH
C0
CH
B1
CH
C1
Figure 3. Parallel Read Access Timing Diagram
CS
t9
t10
t11
t8
WR
tS2
tH4
C
[31:16]
DB[15:0]
C
[15:0]
Word Mode
(WORD/BYTE = 0)
Don’t
Care
C
[31:24]
C
[23:16]
C
[15:8]
C
[7:0]
Byte Mode
(WORD/BYTE = 1)
Figure 4. Parallel Write Access Timing Diagram
16
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
6.13 Typical Characteristics
3.0
3.0
2.5
2.5
2.0
2.0
Integral Nonlinearity (LSB)
Integral Nonlinearity (LSB)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.0
-2.5
-2.5
-3.0
-3.0
0
0
8190 16380 24570 32760 40950 49140 57330 65520
8190 16380 24570 32760 40950 49140 57330 65520
Code
Code
AVDD = BVDD = 5 V
fDATA = max
HVSS = –15 V
Internal reference
HVDD = 15 V
AVDD = BVDD = 5 V
fDATA = max
Figure 5. INL vs Code (ADS8556 ±10-VIN Range)
Figure 6. INL vs Code (ADS8556 ±5-VIN Range)
Differential Nonlinearity (LSB)
1.0
0.5
0
-0.5
1.0
0.5
0
-0.5
-1.0
-1.0
0
0
8190 16380 24570 32760 40950 49140 57330 65520
8190 16380 24570 32760 40950 49140 57330 65520
Code
Code
AVDD = BVDD = 5 V
fDATA = max
HVSS = –15 V
Internal reference
HVDD = 15 V
AVDD = BVDD = 5 V
fDATA = max
Figure 7. DNL vs Code (ADS8556 ±10-VIN Range)
1.0
0.8
0.8
0.6
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
HVSS = –15 V
Internal reference
HVDD = 15 V
Figure 8. DNL vs Code (ADS8556 ±5-VIN Range)
1.0
Integral Nonlinearity (LSB)
Integral Nonlinearity (LSB)
HVDD = 15 V
1.5
1.5
Differential Nonlinearity (LSB)
HVSS = –15 V
Internal reference
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
-1.0
0
2000
4000
6000
8000 10000 12000 14000 16000
0
2000
4000
Code
AVDD = BVDD = 5 V
fDATA = max
6000
8000 10000 12000 14000 16000
Code
HVSS = –15 V
Internal reference
HVDD = 15 V
Figure 9. INL vs Code (ADS8557 ±10-VIN Range)
AVDD = BVDD = 5 V
fDATA = max
HVSS = –15 V
Internal reference
HVDD = 15 V
Figure 10. INL vs Code (ADS8557 ±5-VIN Range)
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
17
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Typical Characteristics (continued)
1.0
1.0
0.8
0.8
Differential Nonlinearity (LSB)
Differential Nonlinearity (LSB)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-0.8
-1.0
-1.0
0
2000
4000
6000
0
8000 10000 12000 14000 16000
2000
4000
6000
AVDD = BVDD = 5 V
fDATA = max
8000 10000 12000 14000 16000
Code
Code
HVSS = –15 V
Internal reference
HVDD = 15 V
AVDD = BVDD = 5 V
fDATA = max
Figure 11. DNL vs Code (ADS8557 ±10-VIN Range)
HVSS = –15 V
Internal reference
HVDD = 15 V
Figure 12. DNL vs Code (ADS8557 ±5-VIN Range)
0.75
0.5
Differential Nonlinearity (LSB)
Integral Nonlinearity (LSB)
0.4
0.50
0.25
0
-0.25
-0.50
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.75
-0.5
0
500
1000
1500
2000
2500
3000
3500
4000
0
500
1000
1500
Code
AVDD = BVDD = 5 V
fDATA = max
2000
2500
3000
3500
4000
Code
HVSS = –15 V
Internal reference
HVDD = 15 V
AVDD = BVDD = 5 V
fDATA = max
Figure 13. INL vs Code (ADS8558)
HVSS = –15 V
Internal reference
HVDD = 15 V
Figure 14. DNL vs Code (ADS8558)
4
0.75
3
0.50
Gain Error (%)
Offset Error (mV)
2
1
0
-1
0.25
0
-0.25
-2
-0.50
-3
-0.75
-4
-40 -25 -10
5
20
35
50
65
80
95
110 125
-40 -25 -10
Temperature (°C)
Figure 15. Offset Error vs Temperature
18
Submit Documentation Feedback
5
20
35
50
65
80
95
110 125
Temperature (°C)
Figure 16. Gain Error vs Temperature
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Typical Characteristics (continued)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
1.40
1.35
-40
Conversion Time (ms)
Power-Supply Rejection Ratio (dB)
-30
-50
-60
-70
1.30
1.25
ADS8556
1.20
ADS8557
1.15
1.10
1.05
ADS8558
1.00
-80
0.95
0.90
-90
0
20
40
60
80
100 120 140 160 180
5
-40 -25 -10
200
20
35
50
65
80
95
110 125
Temperature (°C)
AVDD Noise Frequency (kHz)
CSUPPLY = 100 nF on AVDD
Figure 18. Conversion Time vs Temperature
94
5000
92
4500
90
Signal-to-Noise Ratio (dB)
Number of Occurrences
Figure 17. PSRR vs AVDD Noise Frequency
5500
4000
3500
3000
2500
2000
1500
1000
ADS8556
88
ADS8557
86
84
82
80
78
76
74
ADS8558
72
70
500
-3
-2
-1
0
1
-40 -25 -10
2
5
AVDD = BVDD = 5 V
Range = 4 × VREF
HVSS = –15 V
8192 samples
HVDD = 15 V
Internal reference
AVDD = BVDD = 5 V
Range = ±4 × VREF
Internal reference
Figure 19. Code Histogram (8192 Hits)
35
50
65
80
95
110 125
HVSS = –15 V
fSIGNAL = 10 kHz
HVDD = 15 V
fDATA = max
Figure 20. SNR vs Temperature
-86
94
92
ADS8556
90
Total Harmonic Distortion (dB)
Signal-to-Noise Ratio and Distortion (dB)
20
Temperature (°C)
Code
88
86
ADS8557
84
82
80
78
76
74
ADS8558
72
-88
ADS8558
-90
ADS8557
-92
-94
ADS8556
-96
-98
70
-40 -25 -10
5
20
35
50
65
80
95
110 125
-40 -25 -10
5
AVDD = BVDD = 5 V
Range = ±4 × VREF
Internal reference
HVSS = –15 V
fSIGNAL = 10 kHz
20
35
50
65
80
95
110 125
Temperature (°C)
Temperature (°C)
HVDD = 15 V
fDATA = max
Figure 21. SINAD vs Temperature
AVDD = BVDD = 5 V
Range = ±4 × VREF
Internal reference
HVSS = –15 V
fSIGNAL = 10 kHz
HVDD = 15 V
fDATA = max
Figure 22. THD vs Temperature
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
19
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Typical Characteristics (continued)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
0
-20
98
-40
96
Amplitude (dB)
Spurious-Free Dynamic Range (dB)
100
ADS8556
94
ADS8557
92
90
ADS8558
-60
-80
-100
-120
-140
88
-160
86
-180
-40 -25 -10
5
20
35
50
65
80
95
0
110 125
25
50
75
AVDD = BVDD = 5 V
Range = ±4 × VREF
Internal reference
HVSS = –15 V
fSIGNAL = 10 kHz
HVDD = 15 V
fDATA = max
AVDD = BVDD = 5 V
Range = ±4 × VREF
Internal reference
0
120
-20
115
-40
110
-60
-80
-100
-120
fSAMPLE = 500 kSPS
fSIGNAL = 10 kHz
HVSS = –15 V
HVDD = 15 V
105
100
95
90
-140
85
-160
80
-180
0
25
50
75
100 125 150 175 200 225
250
0
30
60
90
Frequency (kHz)
AVDD = BVDD = 5 V
Range = ±2 × VREF
Internal reference
fSAMPLE = 500 kSPS
fSIGNAL = 10 kHz
HVSS = –15 V
HVDD = 15 V
AVDD = BVDD = 5 V
Range = ±2 × VREF
300
HVSS = –15 V
fDATA = max
HVDD = 15 V
Internal reference
Figure 26. Channel-to-Channel Isolation vs
Input Noise Frequency
2.504
2.504
2.503
2.503
2.502
2.502
VREF (V)
2.501
VREF
2.500
120 150 180 210 240 270
Noise Frequency (kHz)
Figure 25. Frequency Spectrum
(2048-Point FFT, fIN = 10 kHz, ±5-VIN Range)
VREF (V)
250
Figure 24. Frequency Spectrum
(2048-Point FFT, fIN = 10 kHz, ±10-VIN Range)
Isolation (dB)
Amplitude (dB)
Figure 23. SFDR vs Temperature
2.501
2.500
2.499
2.499
2.498
2.498
2.497
2.497
2.496
2.496
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
5.5
-40 -25 -10
Figure 27. Internal Reference Voltage vs
Analog Supply Voltage (2.5-V Mode)
Submit Documentation Feedback
5
20
35
50
65
80
95
110 125
Temperature (°C)
AVDD (V)
20
100 125 150 175 200 225
Frequency (kHz)
Temperature (°C)
Figure 28. Internal Reference Voltage vs
Temperature (2.5-V Mode)
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Typical Characteristics (continued)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
3.005
3.004
3.003
IAVDD (mA)
VREF (V)
3.002
3.001
3.000
2.999
2.998
2.997
2.996
2.995
-40 -25 -10
5
20
35
50
65
80
95
36
34
32
30
28
26
24
22
20
18
16
14
12
10
110 125
fDATA = Max
fDATA = 250kSPS (A-NAP)
-40 -25 -10
5
20
Temperature (°C)
AVDD = 5 V
1.6
A-NAP Mode
1.4
1.2
fDATA = Max
1.0
0.8
0.6
fDATA = 250kSPS (A-NAP)
0.4
0.2
-40 -25 -10
45 90 135 180 225 270 315 360 405 450 495 540 585 630
5
20
35
50
65
80
95
110 125
Temperature (°C)
Internal reference
BVDD = 5 V
Figure 31. ADS8556 Analog Supply Current vs Data Rate
Figure 32. Buffer I/O Supply Current vs Temperature
4.5
4.00
IHVSS (fDATA = Max)
4.0
3.50
Input Supply Current (mA)
Input Supply Current (mA)
110 125
1.8
AVDD = 5 V
IHVDD (fDATA = Max)
2.75
2.50
2.25
IHVSS (250kSPS A-NAP)
1.75
1.50
95
Internal reference
Sample Rate (kSPS)
2.00
80
Normal Operation
0
3.00
65
2.0
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
3.25
50
Figure 30. Analog Supply Current vs Temperature
IBVDD (mA)
IAVDD (mA)
Figure 29. Internal Reference Voltage vs
Temperature (3-V Mode)
3.75
35
Temperature (°C)
IHVDD (250kSPS A-NAP)
IHVSS (fDATA = Max)
3.5
3.0
IHVDD (fDATA = Max)
2.5
2.0
1.5
1.0
IHVSS (250kSPS A-NAP)
0.5
1.25
IHVDD (250kSPS A-NAP)
0
1.00
-40 -25 -10
5
20
35
50
65
80
95
110 125
5
6
7
Range = ±4 × VREF
Internal reference
HVSS = –15 V
8
9
10
11
12
13
14
15
HVDD, |HVSS| (V)
Temperature (°C)
HVDD = 15 V
Figure 33. ADS8556 Input Supply Current vs Temperature
Figure 34. ADS8556 Input Supply Current vs
Input Supply Voltage
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
21
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Typical Characteristics (continued)
at 25°C, over entire supply voltage range, VREF = 2.5 V (internal), and fDATA = maximum (unless otherwise noted)
3.6
IHVSS
3.3
3.0
IHVSS (A-NAP)
IHVxx (mA)
2.7
2.4
2.1
IHVDD (A-NAP)
1.8
1.5
IHVDD
1.2
0.9
0.6
0.3
0
0
90
180
270
360
450
540
630
Data Rate (kSPS)
Range = ±4 × VREF
HVSS = –15 V
HVDD = 15 V
Figure 35. ADS8556 Input Supply Current vs Data Rate
22
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
7 Detailed Description
7.1 Overview
The ADS855x series includes six 16-, 14-, and 12-bit analog-to-digital converters (ADCs) respectively that
operate based on the successive approximation register (SAR) principle. The architecture is designed on the
charge redistribution principle that inherently includes a sample-and-hold function. The six analog inputs are
grouped into three channel pairs. These channel pairs can be sampled and converted simultaneously, preserving
the relative phase information of the signals of each pair. Separate conversion start signals allow simultaneous
sampling on each channel pair: on four channels or on all six channels.
These devices accept single-ended, bipolar analog input signals in the selectable ranges of ±4 VREF or ±2 VREF
with an absolute value of up to ±12 V; see the Analog Inputs section.
The devices offer an internal 2.5-V or 3-V reference source followed by a 10-bit, digital-to-analog converter
(DAC) that allows the reference voltage VREF to be adjusted in 2.44-mV or 2.93-mV steps, respectively.
The ADS855x also offers a selectable parallel or serial interface that can be used in hardware or software mode;
see the Device Configuration section for details.
7.2 Functional Block Diagram
HVDD
HVSS
AVDD
BVDD
Clock
Generator
CH_A0
AGND
SAR ADC
CONVST_A
Control
Logic
REFC_A
CH_A1
AGND
SAR ADC
CH_B0
AGND
BUSY/INT
RANGE/XCLK
HW/SW
REFEN/WR
STBY
RESET
SAR ADC
CONVST_B
Config
Register
REFC_B
CH_B1
AGND
SAR ADC
CH_C0
AGND
SAR ADC
CONVST_C
CS/FS
RD
DB[15:0]
WORD/BYTE
PAR/SER
I/O
REFC_C
CH_C1
AGND
SAR ADC
String
DAC
REF_IO
AGND
2.5V/3V
REF
BGND
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
23
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
7.3 Feature Description
7.3.1 Analog
This section addresses the analog input circuit, the ADCs and control signals, and the reference design of the
device.
7.3.1.1 Analog Inputs
The inputs and the converters are of single-ended, bipolar type. The absolute voltage range can be selected
using the RANGE pin (in hardware mode) or RANGE_x bits (in software mode) in the control register (CR) to
either ±4 VREF or ±2 VREF. With the reference set to 2.5 V (CR bit C18 = 0), the input voltage range can be ±10 V
or ±5 V. With the reference source set to 3 V (CR bit C18 = 1), an input voltage range of ±12 V or ±6 V can be
configured. The logic state of the RANGE pin is latched with the falling edge of BUSY (if CR bit C20 = 0).
The input current on the analog inputs depends on the actual sample rate, input voltage, and signal source
impedance. Essentially, the current into the analog inputs charges the internal capacitor array only during the
sampling period (tACQ). The source of the analog input voltage must be able to charge the input capacitance of
10 pF in ±4-VREF mode or 20 pF in ±2-VREF to a 12-, 14-, 16-bit accuracy level within the acquisition time of 280
ns at maximum data rate; see Figure 1. During the conversion period, there is no further input current flow and
the input impedance is greater than 1 MΩ. To ensure a defined start condition, the sampling capacitors of the
ADS855x are pre-charged to a fixed internal voltage before switching into sampling mode.
To maintain the linearity of the converter, the inputs must always remain within the specified range of HVSS –
0.2 V to HVDD + 0.2 V.
The minimum –3-dB bandwidth of the driving operational amplifier can be calculated using Equation 1:
ln(2) ´ (n + 1)
f-3dB =
2p ´ tACQ
where
•
n = 16, 14, or 12; n is the resolution of the ADS855x
(1)
With a minimum acquisition time of tACQ = 280 ns, the required minimum bandwidth of the driving amplifier is 6.7
MHz for the ADS8556, 6 MHz for the ADS8557, or 5.2 MHz for the ADS8558. The required bandwidth can be
lower if the application allows a longer acquisition time. A gain error occurs if a given application does not fulfill
the bandwidth requirement shown in Equation 1.
A driving operational amplifier may not be required if the impedance of the signal source (RSOURCE) fulfills the
requirement of Equation 2:
tACQ
RSOURCE <
- (RSER + RSW)
CS ln(2) ´ (n + 1)
where
•
•
•
•
n = 16, 14, or 12; n is the resolution of the ADC
CS = 10 pF is the sample capacitor value for VIN = ±4 × VREF mode
RSER = 200 Ω is the input resistor value
RSW = 130 Ω is the switch resistance value
(2)
With tACQ = 280 ns, the maximum source impedance must be less than 2.0 kΩ for the ADS8556, 2.3 kΩ for the
ADS8557, and 2.7 kΩ for the ADS8558 in VIN = ±4 VREF mode or less than 0.8 kΩ for the ADS8556, 1.0 kΩ for
the ADS8557, and 1.2 kΩ for the ADS8558 in VIN = ±2 VREF mode. The source impedance can be higher if the
application allows longer acquisition time.
7.3.1.2 Analog-to-Digital Converter (ADC)
The devices include six ADCs that operate with either an internal or an external conversion clock. The
conversion time can be as low as 1.09 μs with an internal conversion clock (ADS8558). When an external clock
and reference are used, the minimum conversion time is 925 ns.
24
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Feature Description (continued)
7.3.1.3 Conversion Clock
The device uses either an internally-generated or an external (XCLK) conversion clock signal (in software mode
only). In default mode, the device generates an internal clock. When the CLKSEL bit is set high (bit C11 in the
CR), an external conversion clock of up to 20 MHz (max) can be applied on pin 27. In both cases, 18.5 clock
cycles are required for a complete conversion including the pre-charging of the sample capacitors. The external
clock can remain low between conversions.
The conversion clock duty cycle must be 50%. However, the ADS855x functions properly with a duty cycle
between 45% and 55%.
7.3.1.4 CONVST_x
The analog inputs of each channel pair (CH_x0, CH_x1) are held with the rising edge of the corresponding
CONVST_x signal. Only in software mode (except for sequential mode) is CONVST_A used for all six ADCs.
The conversion automatically starts with the next edge of the conversion clock. CONVST_x must remain high
during the entire conversion cycle and the BUSY signal must remain active. A falling edge during an ongoing
conversion puts the related ADC pair into partial power-down mode, see the Reset and Power-Down Modes
section for more details.
For simultaneous sampling, connecting all associated CONVST_x pins together is recommended. If the
CONVST_x signals are not tied together, a maximum skew of 4 ns must be ensured for all three signals in any
order. A CONVST_x signal issued during an ongoing conversion on any channel is blocked, except in sequential
mode; see the Sequential Mode section for more details.
If a parallel interface is used, the behavior of the output port depends on which CONVST_x signals are issued.
Figure 36 shows examples of different scenarios.
BUSY
(C20 = C21 = 0)
CS
CONVST_A
CONVST_C
CONVST_B
RD
DB[15:0]
CH
A0
CH
A1
CH
C0
CH
C1
CH
A0
CH
A1
CH
C0
CH
B0
CH
B1
CH
B0
CH
B1
CH
B0
CH
B1
CH
B0
CONVST_B
CONVST_A
CONVST_B
RD
DB[15:0]
NOTE: Boxed areas indicate the minimum required frame to acquire all data.
Figure 36. Data Output versus CONVST_x
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
25
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Feature Description (continued)
7.3.1.5 BUSY/INT
The BUSY signal indicates if a conversion is in progress. The BUSY signal goes high with a rising edge of any
CONVST_x signal and goes low when the output data of the last channel pair are available in the respective
output register. The readout of the data can be initiated immediately after the falling edge of BUSY. A falling
edge of a CONVST_x input during an ongoing conversion (when BUSY is high) powers down the corresponding
ADC pair.
In sequential mode, the BUSY signal goes low only for one clock cycle; see the Sequential Mode section for
more details.
The polarity of the BUSY/INT signal can be changed using CR bit C20.
7.3.1.6 Reference
The ADS855x provides an internal, low-drift, 2.5-V reference source. To increase the input voltage range, the
reference voltage can be switched to 3-V mode using the VREF bit (bit C18 in the CR). The reference feeds a 10bit string-DAC controlled by bits C[9:0] in the control register. The buffered DAC output is connected to the
REFIO pin. In this way, the voltage at this pin is programmable in 2.44-mV (2.92 mV in 3-V mode) steps and
adjustable to the application needs without additional external components. The actual output voltage can be
calculated using Equation 3:
Range ´ (Code + 1)
VREF =
1024
where
•
•
Range = the chosen maximum reference voltage output range (2.5 V or 3 V)
Code = the decimal value of the DAC register content
(3)
Table 1 lists some examples of internal reference DAC settings with a reference range set to 2.5 V. However, to
ensure proper performance, the DAC output voltage must not be programmed below 0.5 V.
Decouple the buffered output of the DAC with a 100-nF capacitor (minimum); for best performance, a 470-nF
capacitor is recommended. If the internal reference is placed into power-down (default), an external reference
voltage can drive the REFIO pin.
The voltage at the REFIO pin is buffered with three internal amplifiers, one for each ADC pair. The output of
each buffer must be decoupled with a 10-μF capacitor between pin pairs 53 and 54, 55 and 56, and 57 and 58.
The 10-μF capacitors are available as ceramic 0805-SMD components and in X5R quality.
The internal reference buffers can be powered down to decrease the power dissipation of the device. In this
case, external reference drivers can be connected to REFC_A, REFC_B, and REFC_C pins. With 10-μF
decoupling capacitors, the minimum required bandwidth can be calculated using Equation 4:
ln(2)
f-3dB =
2p ´ tCONV
(4)
With the minimum tCONV of 1.09 μs, the external reference buffers require a minimum bandwidth of 102 kHz.
Table 1. DAC Setting Examples (2.5-V Operation)
VREF
DECIMAL CODE
BINARY CODE
HEXADECIMAL CODE
204
00 1100 1100
CC
1.25
511
01 1111 1111
1FF
2.500
1023
11 1111 1111
3FF
OUT
(V)
0.500
26
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
7.3.2 Digital
This section describes the digital control and the timing of the device in detail.
7.3.2.1 Device Configuration
Depending on the desired mode of operation, the ADS855x can be configured using the external pins or the
control register (CR), as shown in Table 2.
Table 2. ADS855x Configuration Settings
HARDWARE MODE (HW/SW = 0)
CONVERSION START CONTROLLED BY SEPARATE
CONVST_x PINS
SOFTWARE MODE (HW/SW = 1)
CONVERSION START CONTROLLED BY CONVST_A
PIN ONLY, EXCEPT IN SEQUENTIAL MODE
Parallel
(PAR/SER = 0)
Configuration using pins, optionally, control bits C[22:18],
C[15:13], and C[9:0]
Configuration using control register bits C[31:0] only;
status of pins 27 (only if used as RANGE input) and 63 is
disregarded
Serial
(PAR/SER = 1)
Configuration using pins, optionally, control bits C[22:18],
C[15:13], and C[9:0]; bits C[31:24] are disregarded
Configuration using control register bits C[31:0] only;
status of pins 1, 27 (only if used as RANGE input), and
63 is disregarded; each access requires a control register
update via SDI (see the Serial Interface section for
details)
INTERFACE MODE
7.3.2.2 Parallel Interface
To use the device with the parallel interface, hold the PAR/SER pin low. The maximum achievable data
throughput rate using the internal clock is 630 kSPS for the ADS8556, 670 kSPS for the ADS8557, and 730
kSPS for the ADS8558 in this case.
Access to the ADS855x is controlled as illustrated in Figure 3 and Figure 4.
The device can either operate with a 16-bit (WORD/BYTE pin set low) or an 8-bit (WORD/BYTE pin set high)
parallel interface. If 8-bit operation is used, the HBEN pin selects if the low-byte (DB7 low) or the high-byte (DB7
high) is available on the data output DB[15:8] first.
7.3.2.3 Serial Interface
The serial interface mode is selected by setting the PAR/SER pin high. In this case, each data transfer starts with
the falling edge of the frame synchronization input (FS). The conversion results are presented on the serial data
output pins SDO_A, SDO_B, and SDO_C depending on the selections made using the SEL_x pins. Starting with
the most significant bit (MSB), the output data are changed at the rising edge of SCLK so that the host processor
can read it at the following falling edge. Output data of the ADS8557 and ADS8558 maintain the 16-bit format
with leading zeros.
Serial data input SDI are latched at the falling edge of SCLK.
The serial interface can be used with one, two, or three output ports. These ports are enabled with pins SEL_A,
SEL_B, and SEL_C. If all three serial data output ports (SDO_A, SDO_B, and SDO_C) are selected, the data
can be read with either two 16-bit data transfers or with one 32-bit data transfer. The data of channels CH_x0 are
available first, followed by data from channels CH_x1. The maximum achievable data throughput rate is 450
kSPS for the ADS8556, 470 kSPS for the ADS8557, and 500 kSPS for the ADS8558 in this case.
If the application allows a data transfer using two ports only, then the SDO_A and SDO_B outputs are used. The
device outputs data from channel CH_A0 followed by CH_A1 and CH_C0 on SDO_A and data from channel
CH_B0 followed by CH_B1 and CH_C1 occurs on SDO_B. In this case, a data transfer of three consecutive 16bit words or one continuous 48-bit word is supported. The maximum achievable data throughput rate is 375
kSPS for the ADS8556, 390 kSPS for the ADS8557, and 400 kSPS for the ADS8558.
The output SDO_A is selected if only one serial data port is used in the application. Data are available in the
following order: CH_A0, CH_A1, CH_B0, CH_B1, CH_C0, and, finally CH_C1. Data can be read using six 16-bit
transfers, three 32-bit transfers, or a single 96-bit transfer. The maximum achievable data throughput rate is 250
kSPS for the ADS8556, ADS8557 and 260 kSPS for the ADS8558 in this case.
Figure 2 (the serial operation timing diagram) and Figure 37 illustrate all possible scenarios in more detail.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
27
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
CONVST_A
CONVST_B
CONVST_C
BUSY
(C20 = C21 = 0)
48 SCLKs
SEL_A = SEL_B = 1, SEL_C = 0
FS
SDO_A
CHA0
CHA1
CHC0
SDO_B
CHB0
CHB1
CHC1
SEL_A = 1, SEL_B = SEL_C = 0
96 SCLKs
FS
SDO_A
CHA0
CHA1
CHB0
CHB1
CHC0
CHC1
Figure 37. Serial Interface: Data Output with One or Two Active SDOs
7.3.2.4 Output Data Format
The data output format of the ADS855x is binary twos complement, as shown in Table 3.
For the ADS8557, which delivers 14-bit conversion results, the leading two bits of the 16-bit frame are '0' in the
serial interface mode. In parallel interface mode, the output pins DB[15:14] are held low.
Respectively, when the ADS8558 outputs 12 bits of data, the first four bits of a serial 16-bit frame are zeros, in
parallel interface mode the output pins DB[15:12] are held low.
Table 3. Output Data Format
DESCRIPTION
Positive full-scale
INPUT VOLTAGE VALUE
4 VREF or 2 VREF
BINARY CODE (HEXADECIMAL CODE)
ADS8556
ADS8557
ADS8558
0111 1111 1111 1111 (7FFF)
0001 1111 1111 1111 (1FFF)
0000 0111 1111 1111 (7FF)
Midscale + 0.5LSB
VREF / (2 × resolution)
0000 0000 0000 0000 (0000)
0000 0000 0000 0000 (0000)
0000 0000 0000 0000 (0000)
Midscale – 0.5LSB
–VREF / (2 × resolution)
1111 1111 1111 1111 (FFFF)
0011 1111 1111 1111 (3FFF)
0000 1111 1111 1111 (FFF)
Negative full-scale
–4 VREF or –2 VREF
1000 0000 0000 0000 (8000)
0010 0000 0000 0000 (2000)
0000 1000 0000 0000 (800)
7.4 Device Functional Modes
7.4.1 Hardware Mode
With the HW/SW input (pin 62) set low, the device functions are controlled via the pins and, optionally, control
register bits C[22:18], C[15:13], and C[9:0].
Generally, the device can be used in hardware mode and switched into software mode to initialize or adjust the
control register settings (for example, the internal reference DAC) and switched back to hardware mode
thereafter.
7.4.2 Software Mode
When the HW/SW input is set high, the device operates in software mode with functionality set only by the
control register bits (corresponding pin settings are ignored).
28
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Device Functional Modes (continued)
If the parallel interface is used, an update of all control register settings is performed by issuing two 16-bit write
accesses on pins DB[15:0] in word mode or four 8-bit accesses on pins DB[15:8] in byte mode (to avoid losing
data, the entire sequence must be finished before starting a new conversion). Hold CS low during the two or four
write accesses to completely update the configuration register. Updating only the upper eight bits (C[31:24]) is
also possible using a single write access and pins DB[15:8] in both word and byte modes. In word mode, the first
write access updates only the upper eight bits and stores the lower eight bits (C[23:16]) for an update that takes
place with the second write access along with C[15:0].
If the serial interface is used, input data containing control register contents are required with each read access
to the device in this mode (combined read/write access). For initialization purposes, all 32 bits of the register
must be set (bit C16 must be set to '1' during that access to allow the update of the entire register content). To
minimize switching noise on the interface, an update of the first eight bits (C[31:24]) with the remaining bits held
low can be performed thereafter.
Figure 42 illustrates the different control register update options.
7.4.3 Daisy-Chain Mode (in Serial Mode Only)
The serial interface of the ADS855x supports a daisy-chain feature that allows cascading of multiple devices to
minimize the board space requirements and simplify routing of the data and control lines. In this case, pins
DB5/DCIN_A, DB4/DCIN_B, and DB3/DCIN_C are used as serial data inputs for channels A, B, and C,
respectively. Figure 38 shows an example of a daisy-chain connection of three devices sharing a common
CONVST line to allow simultaneous sampling of 18 analog channels along with the corresponding timing
diagram. To activate the daisy-chain mode, the DCEN pin must be pulled high. As a result of the time
specifications tS1, tH1, and tD3, the maximum SCLK frequency that can be used in daisy-chain mode is 27.78 MHz
(assuming a 50% duty cycle).
CONVST
FS
SCLK
ADS8556
#1
ADS8556
#2
ADS8556
#3
CONVST_A
CONVST_A
CONVST_A
FS
SCLK
FS
SCLK
FS
SCLK
DCIN_A
DCIN_B
DCIN_C
SDO_A
SDO_B
SDO_C
DCEN = 0
SDO_A
SDO_B
SDO_C
DCIN_A
DCIN_B
DCIN_C
DCEN = 1
SDO_A
SDO_B
SDO_C
To
Processing
Unit
DCEN = 1
CONVST
BUSY
(C20 = C21 = 0)
FS
SDO_x #3
Don’t Care
16-Bit Data CHx0
ADS8556 #3
16-Bit Data CHx1
ADS8556 #3
16-Bit Data CHx0
ADS8556 #2
16-Bit Data CHx1
ADS8556 #2
16-Bit Data CHx0
ADS8556 #1
16-Bit Data CHx1
ADS8556 #1
Figure 38. Example of Daisy-Chaining Three ADS8556s
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
29
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Device Functional Modes (continued)
7.4.4 Sequential Mode (in Software Mode with External Conversion Clock Only)
The three channel pairs of the ADS855x can be run in sequential mode, with the corresponding CONVST_x
signals interleaved, when an external clock is used. To activate the device in sequential mode, CR bits C11
(CLKSEL) and C23 (SEQ) must be asserted. In this case, the BUSY output indicates a finished conversion by
going low (when C20 = 0) or high (when C20 = 1) for only a single conversion clock cycle in case of ongoing
conversions of any other channel pairs. Figure 39 shows the behavior of the BUSY output in this mode. Initiate
each conversion start during the high phase of the external clock, as shown in Figure 39. The minimum time
required between two CONVST_x pulses is the time required to read the conversion result of a channel (pair).
XCLK
EOC
CHBx
(1)
EOC
CHAx
(1)
CONVST_A
EOC
CHCx
(1)
CONVST_B
CONVST_C
tCCLK
BUSY
(C20 = 0)
CS
RD
CH
A0
D[15:0]
(1)
CH
A1
CH
B0
CH
B1
CH
C0
CH
C1
EOC = end of conversion (internal signal).
Figure 39. Sequential Mode Timing
7.4.5 Reset and Power-Down Modes
The device supports two reset mechanisms: a power-on reset (POR) and a pin-controlled reset (RESET) that
can be issued using pin 28. Both the POR and RESET act as a master reset that causes any ongoing
conversion to be interrupted, the control register content to be set to the default value, and all channels to be
switched into sample mode.
When the device is powered up, the POR sets the device in default mode when AVDD reaches 1.5 V. When the
device is powered down, the POR circuit requires AVDD to remain below 125 mV at least 350 ms to ensure
proper discharging of internal capacitors and to ensure correct behavior of the device when powered up again. If
the AVDD drops below 400 mV but remains above 125 mV (see the undefined zone in Figure 40), the internal
POR capacitor does not discharge fully and the device requires a pin-controlled reset to perform correctly after
the recovery of AVDD.
30
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Device Functional Modes (continued)
AVDD (V)
5.500
Specified Supply
Voltage Range
5.000
4.500
4.000
3.000
2.000
POR
Trigger Level
1.500
1.000
0.400
0.125
Undefined Zone
0
0.350
t (s)
Figure 40. POR: Relevant Voltage Levels
The entire device, except the digital interface, can be powered down by pulling the STBY pin low (pin 24).
Because the digital interface section remains active, data can be retrieved when in stand-by mode. To power the
part on again, the STBY pin must be brought high. The device is ready to start a new conversion after the 10 ms
required to activate and settle the internal circuitry. This user-controlled approach can be used in applications
that require lower data throughput rates and lowest power dissipation. The content of CR is not changed during
standby mode. A pin-controlled reset is not required after returning to normal operation.
Although the standby mode affects the entire device, each device channel pair can also be individually switched
off by setting control register bits C[15:13] (PD_x). When reactivated, the relevant channel pair requires 10 ms to
fully settle before starting a new conversion. The internal reference remains active, except all channels are
powered down at the same time.
In partial power-down mode, each of the three channel pairs of the ADS855x can be individually put into a
power-saving condition that reduces the current requirement to 2 mA per channel pair by bringing the
corresponding CONVST_x signal low during an ongoing conversion when BUSY is high. The relevant channel
pair is activated again by issuing a RESET pulse (to avoid loss of data from the active channels, this RESET
pulse must be generated after retrieving the latest conversion results). The next rising edge of the CONVST_x
signal must be issued at least six conversion cycle periods after the reset pulse and starts a new conversion; see
Figure 41. The internal reference remains active during the partial power-down mode.
The auto-NAP power-down mode is enabled by asserting the A-NAP bit (C22) in the control register. If the autoNAP mode is enabled, the ADS855x automatically reduces the current requirement to 6 mA after finishing a
conversion; thus, the end of conversion actually activates the power-down mode. Triggering a new conversion by
applying a positive CONVST_x edge puts the device back into normal operation, starts the acquisition of the
analog input, and automatically starts a new conversion six conversion clock cycles later. Therefore, a complete
conversion cycle takes 24.5 conversion clock cycles; thus, the maximum throughput rate in auto-NAP powerdown mode is reduced to a maximum of 380 kSPS for the ADS8556, 395 kSPS for the ADS8557, and 420 kSPS
for the ADS8558 in serial mode. In parallel mode, the maximum data rates are 500 kSPS for the ADS8556,
530 kSPS for the ADS8557, and 580 kSPS for the ADS8558. The internal reference remains active during the
auto-NAP mode. Table 4 compares the analog current requirements of the devices in the different modes.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
31
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Device Functional Modes (continued)
BUSY
CONVST_A/C
ADC CH_Ax/Cx ACQ
ACQ
CONV
CONV
ACQ
CONV
ACQ
CONVST_B
6 ´ tCCLK Min
RESET
ADC CH_Bx
ACQ CONV
Power-Down
ACQ
Figure 41. Partial Power-Down
Table 4. Maximum Analog Current (IAVDD) Demand of the ADS855x
OPERATIONAL
MODE
ANALOG
CURRENT (IAVDD)
ENABLED BY
ACTIVATED BY
NORMAL
OPERATION TO
POWER-DOWN
DELAY
RESUMED BY
POWER-UP TO
NORMAL
OPERATION
DELAY
POWER-UP TO
NEXT
CONVERSION
START TIME
DISABLED BY
Normal operation
12 mA/channel
pair (maximum
data rate)
Power on
CONVST_x
—
—
—
—
Power off
Partial powerdown of channel
pair x
2 mA (channel
pair x)
Power on
CONVST_x low
while BUSY is
high
At falling edge of
BUSY
RESET pulse
Immediate
6 × tCCLK
Power off
Auto-NAP
6 mA
A-NAP = 1 (CR
bit)
Each end of
conversion
At falling edge of
BUSY
CONVST_x
Immediate
6 × tCCLK
A-NAP = 0 (CR
bit)
Power-down of
channel pair x
16 μA (channel
pair x)
HW/SW = 1
PD_x = 1 (CR bit)
Immediate
PD_x = 0 (CR bit)
Immediate after
completing
register update
10 ms
HW/SW = 0
Stand-by
50 μA
Power on
STBY = 0
Immediate
STBY = 1
Immediate
10 ms
Power off
7.5 Register Maps
7.5.1 Control Register (CR); Default Value = 0x000003FF
The control register settings can only be changed in software mode and are not affected when switching to
hardware mode thereafter. The register values are independent from input pin settings. Changes are active with
the rising edge of WR in parallel interface mode or with the 32nd falling SCLK edge of the access in which the
register content is updated in serial mode. Optionally, the register can also be partially updated by writing only
the upper eight bits (C[31:24]). The control register update options are provided in Figure 42. The CR content is
defined in Table 5.
32
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Register Maps (continued)
RESET
(or Power-Up)
BUSY
(C20 = C21 = 0)
PAR/SER = 1
FS
C[31:0]
Initialization Data
SDI
Continuous Update
Continuous Update
C
[31:24]
C
[31:24]
PAR/SER = 0; WORD/BYTE = 0
CS
WR
Initialization Data
C
[31:16]
DB[15:0]
Update
C
[15:0]
C
[31:24]
C
[15:0]
PAR/SER = 0; WORD/BYTE = 1
WR
Initialization Data
C
[31:24]
DB[15:8]
C
[23:16]
C
[15:8]
Update
C
[31:24]
C
[7:0]
C
[23:16]
Figure 42. Control Register Update Options
Table 5. Control Register (CR)
DESCRIPTION
ACTIVE IN
HARDWARE
MODE
BIT
NAME
C31
CH_C
0 = Channel pair C disabled for next conversion (default)
1 = Channel pair C enabled
No
C30
CH_B
0 = Channel pair B disabled for next conversion (default)
1 = Channel pair B enabled
No
C29
CH_A
0 = Channel pair A disabled for next conversion (default)
1 = Channel pair A enabled
No
C28
RANGE_C
0 = Input voltage range selection for channel pair C: 4 VREF (default)
1 = Input voltage range selection for channel pair C: 2 VREF
No
C27
RANGE_B
0 = Input voltage range selection for channel pair B: 4 VREF (default)
1 = Input voltage range selection for channel pair B: 2 VREF
No
C26
RANGE_A
0 = Input voltage range selection for channel pair A: 4 VREF (default)
1 = Input voltage range selection for channel pair A: 2 VREF
No
C25
REFEN
0 = Internal reference source disabled (default)
1 = Internal reference source enabled
No
C24
REFBUF
0 = Internal reference buffers enabled (default)
1 = Internal reference buffers disabled
No
C23
SEQ
0 = Sequential convert start mode disabled (default)
1 = Sequential convert start mode enabled (bit 11 must be '1' in this case)
No
C22
A-NAP
0 = Normal operation (default)
1 = Auto-NAP feature enabled
Yes
C21
BUSY/INT
0 = BUSY/INT pin in normal mode (BUSY) (default)
1 = BUSY/INT pin in interrupt mode (INT)
Yes
C20
BUSY L/H
0 = BUSY active high when INT is active low (default)
1 = BUSY active low when INT is active high
Yes
C19
Don’t use
This bit is always set to '0'
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
—
Submit Documentation Feedback
33
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Register Maps (continued)
Table 5. Control Register (CR) (continued)
34
ACTIVE IN
HARDWARE
MODE
BIT
NAME
DESCRIPTION
C18
VREF
0 = Internal reference voltage: 2.5 V (default)
1 = Internal reference voltage: 3 V
Yes
C17
READ_EN
0 = Normal operation (conversion results available on SDO_x) (default)
1 = Control register contents output on SDO_x with next access
Yes
C16
C23:0_EN
0 = Control register bits C[31:24] update only (serial mode only) (default)
1 = Entire control register update enabled (serial mode only)
Yes
C15
PD_C
0 = Normal operation (default)
1 = Power-down for channel pair C enabled (bit 31 must be '0' in this case)
Yes
C14
PD_B
0 = Normal operation (default)
1 = Power-down for channel pair B enabled (bit 30 must be '0' in this case)
Yes
C13
PD_A
0 = Normal operation (default)
1 = Power-down for channel pair A enabled (bit 29 must be '0' in this case)
Yes
C12
Don't use
This bit is always '0'
—
C11
CLKSEL
0 = Normal operation with internal conversion clock (mandatory in hardware mode) (default)
1 = External conversion clock (applied through pin 27) used
No
C10
CLKOUT_EN
0 = Normal operation (default)
1 = Internal conversion clock available at pin 27
No
C9
REFDAC[9]
Bit 9 (MSB) of reference DAC value; default = 1
Yes
C8
REFDAC[8]
Bit 8 of reference DAC value; default = 1
Yes
C7
REFDAC[7]
Bit 7 of reference DAC value; default = 1
Yes
C6
REFDAC[6]
Bit 6 of reference DAC value; default = 1
Yes
C5
REFDAC[5]
Bit 5 of reference DAC value; default = 1
Yes
C4
REFDAC[4]
Bit 4 of reference DAC value; default = 1
Yes
C3
REFDAC[3]
Bit 3 of reference DAC value; default = 1
Yes
C2
REFDAC[2]
Bit 2 of reference DAC value; default = 1
Yes
C1
REFDAC[1]
Bit 1 of reference DAC value; default = 1
Yes
C0
REFDAC[0]
Bit 0 (LSB) of reference DAC value; default = 1
Yes
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The ADS855x devices enable high-precision measurement of up to six analog signals simultaneously. The
following sections summarize some of the typical use cases for the ADS855x devices and the main steps and
components used around the analog-to-digital converter. The design example is carried out specifically using the
ADS8556 for a 16-bit data acquisition system.
8.2 Typical Application
This section describes the measurement of electrical variables in a 3-phase power system. The accurate
measurement of electrical variables in a power grid is extremely critical because this measurement helps
determine the operating status and running quality of the grid. Such accurate measurements also help diagnose
problems with the power network, thereby enabling prompt solutions and minimizing down time. The key
electrical variables measured in 3-phase power systems are the three line voltages and the three line currents;
see Figure 43. These variables enable metrology and power automation systems to determine the amplitude,
frequency, and phase information to perform harmonic analysis, power factor calculation, power quality
assessment, and so forth.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
35
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Typical Application (continued)
0.1 F
HVDD
OPA2277
50 k
ADS855x
From
Reference
Block
REFIO
49.9
0.47 F
BVDD
CH_A1
HVSS
100 k
From analog
front ends of
CH_B1 and
CH_C1.
370 pF
0.1 F
100 k
To analog front ends of
CH_B1 and CH_C1.
PT3
REFEN/WR
HW/SW
PAR/SER
370 pF
HVSS
WORD/BYTE
+15 V
HVDD
100 k
820 pF
10 F
0.1 F
10 F
0.1 F
-15 V
CT1
AGND
HVSS
+5 V
AVDD
40 F
Phase A
AGND
+3.3 V
Phase B
BVDD
CT2
1 F
Neutral
BGND
REFCP
Load
Three Phase
Power System
RANGE
CH_A0
100 k
PT2
CH_C1
HVDD
OPA2277 49.9
50 k
820 pF
PT1
CH_B1
STBY
Phase C
CT3
10 F
From analog
front end of
CH_C0.
CH_C0
REFBP
10 F
To analog front ends of
CH_B0 and CH_C0.
REFCN
From analog
front end of
CH_B0.
REFBN
CH_B0
REFAP
10 F
REFAN
CONVST_A
CONVST_B
CONVST_C
RESET
CS
RD
DB[15:0]
Host
Controller
Figure 43. Simultaneous Acquisition of Voltage and Current in a 3-Phase Power System
8.2.1 Design Requirements
To
•
•
•
•
•
•
36
begin the design process, a few parameters must be decided upon. The designer must know the following:
Output range of the potential transformers (elements labeled PT1, PT2, and PT3 in Figure 43)
Output range of the current transformers (elements labeled CT1, CT2, and CT3 in Figure 43)
Input impedance required from the analog front-end for each channel
Fundamental frequency of the power system
Number of harmonics that must be acquired
Type of signal conditioning required from the analog front end for each channel
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
Typical Application (continued)
8.2.2 Detailed Design Procedure
Figure 44 shows the topology chosen to meet the design requirements. A feedback capacitor CF is included to
provide a low-pass filter characteristic and attenuate signals outside the band of interest.
C1
R1
HVDD
R2
Vout
RIN
To ADS855x
input
C2
HVSS
RF
Vin
From PT
or CT
CF
Figure 44. Operational Amplifier in an Inverting Configuration
The potential transformers (PTs) and current transformers (CTs) used in the system depicted in Figure 43
provide the six input variables required. These transformers have a ±10-V output range. Although the PTs and
CTs provide isolation from the power system, the value of RIN is selected as 100 kΩ to provide an additional,
high-impedance safety element to the input of the ADC. Moreover, selecting a low-frequency gain of –1 V/V (as
shown in Equation 5) provides a ±10-V output that can be fed into the ADS8556 device; therefore, the value of
RF is selected as 100 kΩ.
V out
Low f
RF
V in
R IN
100 k :
Vin
100 k :
V in
(5)
The primary goal of the acquisition system depicted in Figure 43 is to measure up to 20 harmonics in a 60-Hz
power network. Thus, the analog front-end must have sufficient bandwidth to detect signals up to 1260 Hz, as
shown in Equation 6.
f MAX
( 20 1) 60 Hz
1260 Hz
(6)
Based on the bandwidth found in Equation 6, the ADS8556 device is set to simultaneously sample all six
channels at 15.36 kSPS, which provides enough samples to clearly resolve even the highest harmonic required.
The passband of the configuration shown in Figure 44 is determined by the –3-dB frequency according to
Equation 7. The value of CF is selected as 820 pF, which is a standard capacitance value available in 0603 size
(surface-mount component) and such values, combined with that of RF, result in sufficient bandwidth to
accommodate the required 20 harmonics (at 60 Hz).
f
3 dB
1
2S R F C F
1
2S (100 k : )( 820 pF )
1940 Hz
(7)
The value of R1 is selected as the parallel combination of RIN and RF to prevent the input bias current of the
operational amplifier from generating an offset error.
The value of component C1 is chosen as 0.1 µF to provide a low-impedance path for noise signals that can be
picked up by R1; this 0.1-µF capacitance value improves the EMI robustness and noise performance of the
system.
The OPA2277 device is chosen for its low input offset voltage, low drift, bipolar swing, sufficient gain-bandwidth
product and low quiescent current. For additional information on the procedure to select SAR ADC input drivers,
see 16-bit 400KSPS 4-Ch. Multiplexed Data Acquisition Ref Design for High Voltage Inputs, Low Distortion,
TIPD151.
The charge injection damping circuit is composed of R2 (49.9 Ω) and C2 (370 pF); these components reject highfrequency noise and meet the settling requirements of the ADS8556 device input.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
37
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
Typical Application (continued)
Figure 45 shows the reference block used in this design.
REF5025
AVDD
10
10 F
0.1 F
OPA211
OUT
VIN
100
To REFIO
1
GND
TRIM
AGND
47 F
47 F 10 nF
AVDD
47 F
1 F
10 nF
22 F
49.9
Figure 45. Reference Block
For more information on the design of charge injection damping circuits and reference driving circuits for SAR
ADCs, consult the reference guide Power-optimized 16-bit 1MSPS Data Acquisition Block for Lowest Distortion
and Noise Reference Design, TIDU014.
8.2.3 Application Curve
Figure 46 shows the frequency spectrum of the data acquired by the ADS8556 device for a sinusoidal, 20-VPP
input at 60 Hz.
Figure 46. Frequency Spectrum for a Sinusoidal 20-VPP Signal at 60 Hz
The ac performance parameters are:
• SNR: 91.9 dB
• THD: –99.68 dB
• SNDR: 91.23 dB
• SFDR: 103.65 dB
38
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
9 Power Supply Recommendations
The ADS855x requires four separate supplies: the analog supply for the ADC (AVDD), the buffer I/O supply for
the digital interface (BVDD), and the high-voltage supplies driving the analog input circuitry (HVDD and HVSS).
Generally, there are no specific requirements with regard to the power sequencing of the device. However, when
HVDD is supplied before AVDD, the internal ESD structure conducts, increasing IHVDD beyond the specified
value.
The AVDD supply provides power to the internal circuitry of the ADC. AVDD can be set in the range of 4.5 V to
5.5 V. Because the supply current of the device is typically 30 mA, a passive filter cannot be used between the
digital board supply of the application and the AVDD pin. A linear regulator is recommended to generate the
analog supply voltage. Decouple each AVDD pin to AGND with a 100-nF capacitor. In addition, place a single
10-μF capacitor close to the device but without compromising the placement of the smaller capacitor. Optionally,
each supply pin can be decoupled using a 1-μF ceramic capacitor without the requirement for a 10-μF capacitor.
The BVDD supply is only used to drive the digital I/O buffers and can be set in the range of 2.7 V to 5.5 V. This
range allows the device to interface with most state-of-the-art processors and controllers. To limit the noise
energy from the external digital circuitry to the device, filter BVDD. A 10-Ω resistor can be placed between the
external digital circuitry and the device because the current drawn is typically below 2 mA (depending on the
external loads). Place a bypass ceramic capacitor of 1-μF (or alternatively, a pair of 100-nF and 10-μF
capacitors) between the BVDD pin and pin 8.
The high-voltage supplies (HVSS and HVDD) are connected to the analog inputs. Noise and glitches on these
supplies directly couple into the input signals. Place a 100-nF ceramic decoupling capacitor, located as close to
the device as possible, between each of pins 30, 31, and AGND. An additional 10-μF capacitor is used that must
be placed close to the device but without compromising the placement of the smaller capacitor.
10 Layout
10.1 Layout Guidelines
All GND pins must be connected to a clean ground reference. Keep this connection as short as possible to
minimize the inductance of this path. Using vias connecting the pads directly to the ground plane is
recommended. In designs without ground planes, keep the ground trace as wide as possible. Avoid connections
that are too close to the grounding point of a microcontroller or digital signal processor.
Depending on the circuit density on the board, placement of the analog and digital components, and the related
current loops, a single solid ground plane for the entire printed circuit board (PCB) or a dedicated analog ground
area can be used. In case of a separated analog ground area, ensure a low-impedance connection between the
analog and digital ground of the ADC by placing a bridge underneath (or next) to the ADC. Otherwise, even short
undershoots on the digital interface lower than –300 mV lead to the conduction of ESD diodes causing current
flow through the substrate and degrading the analog performance.
During PCB layout, care must be taken to avoid any return currents crossing sensitive analog areas or signals.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
39
ADS8556, ADS8557, ADS8558
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
www.ti.com
10.2 Layout Example
Figure 47 shows a layout recommendation for the ADS855x along with the proper decoupling and reference
capacitor placement and connections.
ADS8556/7/8
Top View
To AVDD
To AVDD
To DUT
AVDD Source
10
mF
AVDD
51
0.1mF
AGND
54
0.47mF
AGND
56
10mF
AGND
58
10mF
AGND
61
AGND
62
10mF
1
48
2
AVDD
3
AVDD
4
45
5
AGND
6
AGND
7
42
BGND
AVDD
BVDD
AVDD
10
39
14
AVDD
15
AVDD
16
33
17
18
19
20
21 22
23
24
0.1mF
To
AVDD
LEGEND
27
28
29
0.1
mF
To AVDD
0.1
mF
0.1
mF
To AVDD
0.1
mF
0.1
mF
To AVDD
0.1
mF
AGND
36
HVDD
AGND
13
HVSS
AGND
AVDD
11
12
AGND
1
mF
To
BVDD
63
AVDD
64
AGND
0.1mF
0.1mF
0.1mF
10mF
10mF
To
HVSS/HVDD
TOP layer; copper pour and traces
Lower layer; AGND area
Lower layer; BGND area
Via
(1)
All 0.1-μF, 0.47-μF, and 1-μF capacitors must be placed as close to the device as possible.
(2)
All 10-μF capacitors must be close to the device but without compromising the placement of the smaller capacitors.
Figure 47. Layout Recommendation
40
Submit Documentation Feedback
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
ADS8556, ADS8557, ADS8558
www.ti.com
SBAS404D – OCTOBER 2006 – REVISED FEBRUARY 2016
11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
• OPAx277 Data Sheet, SBOS079
• REF5025 Data Sheet, SBOS410
• 16-bit 400KSPS 4-Ch. Multiplexed Data Acquisition Ref Design for High Voltage Inputs, Low Distortion,
TIPD151
• Power-optimized 16-bit 1MSPS Data Acquisition Block for Lowest Distortion and Noise Reference Design,
TIDU014
11.2 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 6. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
ADS8556
Click here
Click here
Click here
Click here
Click here
ADS8557
Click here
Click here
Click here
Click here
Click here
ADS8558
Click here
Click here
Click here
Click here
Click here
11.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
Copyright © 2006–2016, Texas Instruments Incorporated
Product Folder Links: ADS8556 ADS8557 ADS8558
Submit Documentation Feedback
41
PACKAGE OPTION ADDENDUM
www.ti.com
2-Feb-2016
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
ADS8556IPM
ACTIVE
LQFP
PM
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8556I
ADS8556IPMR
ACTIVE
LQFP
PM
64
1000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8556I
ADS8557IPM
ACTIVE
LQFP
PM
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8557I
ADS8557IPMR
ACTIVE
LQFP
PM
64
1000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8557I
ADS8558IPM
ACTIVE
LQFP
PM
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8558I
ADS8558IPMR
ACTIVE
LQFP
PM
64
1000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
-40 to 125
ADS
8558I
(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.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
2-Feb-2016
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
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 2
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Feb-2016
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
ADS8556IPMR
LQFP
PM
64
1000
330.0
24.4
13.0
13.0
2.1
16.0
24.0
Q2
ADS8557IPMR
LQFP
PM
64
1000
330.0
24.4
13.0
13.0
2.1
16.0
24.0
Q2
ADS8558IPMR
LQFP
PM
64
1000
330.0
24.4
13.0
13.0
2.1
16.0
24.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Feb-2016
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
ADS8556IPMR
LQFP
PM
64
1000
367.0
367.0
45.0
ADS8557IPMR
LQFP
PM
64
1000
367.0
367.0
45.0
ADS8558IPMR
LQFP
PM
64
1000
367.0
367.0
45.0
Pack Materials-Page 2
MECHANICAL DATA
MTQF008A – JANUARY 1995 – REVISED DECEMBER 1996
PM (S-PQFP-G64)
PLASTIC QUAD FLATPACK
0,27
0,17
0,50
0,08 M
33
48
49
32
64
17
0,13 NOM
1
16
7,50 TYP
Gage Plane
10,20
SQ
9,80
12,20
SQ
11,80
0,25
0,05 MIN
0°– 7°
0,75
0,45
1,45
1,35
Seating Plane
0,08
1,60 MAX
4040152 / C 11/96
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Falls within JEDEC MS-026
May also be thermally enhanced plastic with leads connected to the die pads.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
Automotive and Transportation
www.ti.com/automotive
Amplifiers
amplifier.ti.com
Communications and Telecom
www.ti.com/communications
Data Converters
dataconverter.ti.com
Computers and Peripherals
www.ti.com/computers
DLP® Products
www.dlp.com
Consumer Electronics
www.ti.com/consumer-apps
DSP
dsp.ti.com
Energy and Lighting
www.ti.com/energy
Clocks and Timers
www.ti.com/clocks
Industrial
www.ti.com/industrial
Interface
interface.ti.com
Medical
www.ti.com/medical
Logic
logic.ti.com
Security
www.ti.com/security
Power Mgmt
power.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Microcontrollers
microcontroller.ti.com
Video and Imaging
www.ti.com/video
RFID
www.ti-rfid.com
OMAP Applications Processors
www.ti.com/omap
TI E2E Community
e2e.ti.com
Wireless Connectivity
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2016, Texas Instruments Incorporated