TI AMC7823IRTAT

 AMC7823
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ANALOG MONITORING AND CONTROL CIRCUIT
FEATURES
APPLICATIONS
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
12-Bit ADC (200 kSPS)
– Eight Analog Inputs
– Input Range 0 to 2 × VREF
Programmable VREF, 1.25 V or 2.5 V
Eight 12-Bit DACs (2-µs Settling Time)
Four Analog Input Out-of-Range Alarms
Six General-Purpose Digital I/O
Internal Bandgap Reference
On-Chip Temperature Sensor
Precision Current Source
SPI™ Interface, 3-V or 5-V Logic Compatible
Single 3-V to 5-V Supply
Power-Down Mode/Low Power
Small Package (QFN-40, 6 × 6 mm)
Communications Equipment
Optical Networks
Automatic Test Equipment
Industrial Control and Monitor
Medical Equipment
DESCRIPTION
The AMC7823 is a complete analog monitoring and
control circuit that includes an 8-channel, 12-bit
analog-to-digital converter (ADC), eight 12-bit digitalto-analog converters (DACs), four analog input
out-of-range alarms, and six GPIOs to monitor analog
signals and control external devices. Also, the
AMC7823 has an internal sensor to monitor chip
temperature, and a precision current source to drive
remote thermistors, or RTDs, to monitor remote
temperatures.
Range
Threshold
Sync. Load
(Ext./Internal)
Analog Input Signal Ground
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
Out-of-Range
Alarm
DAC 0_OUT
DAC-0
ADC
ADC Trigger
(External / Internal)
CH8
DAC 7_OUT
DAC-7
Channel Select
TEMP
On-Chip
Temperature
Sensor
Ext. Ref _ IN
Reference
Precision_Current
Current_Setting Resistor
Serial-Parallel Shift Reg
BVDD
DGND
DVDD
AVDD
AGND
GPIO-5
GPIO-4
GPIO-3 / ALR3
GPIO-0 / ALR0
DAV
GALR
RESET
MISO
SS
MOSI
SPI Interface
SCLK
ELDAC
CONVERT
(Ext. ADC
Trigger)
(Ext. DAC
Sync Load)
Registers and
Control Logic
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SPI is a trademark of Motorola, Inc.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2005, Texas Instruments Incorporated
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
DESCRIPTION (CONTINUED)
The AMC7823 has an internal programmable reference (+2.5 V or +1.25 V), and an SPI serial interface. An
external reference can be used as well. Typical power dissipation is 100 mW. The analog input range is 0 V to
+5 V, and the analog output range is 0 V to +2.5 V or 0 V to +5 V. The AMC7823 is ideal for multichannel
applications where low power and small size are critical. The AMC7823 is available in a 40-lead QFN package
and is fully specified over the –40°C to +85°C temperature range.
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated
circuits be handled with appropriate precautions. Failure to observe proper handling and installation
procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision
integrated circuits may be more susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
PACKAGE/ORDERING INFORMATION (1)
PRODUCT
PACKAGELEAD
(DESIGNATOR)
SPECIFIED
TEMPERATURE
RANGE
AMC7823
QFN-40 (RTA)
–40°C to 85°C
(1)
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
AMC7823
AMC7823IRTAT
Tape and Reel, 250
AMC7823
AMC7823IRTAR
Tape and Reel, 2000
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS
Over operating free-air temperature range unless otherwise noted( (1))
AMC7823
UNIT
AVDD, DVDD, BVDD to GND
–0.3 to +6
V
Digital input voltage to GND
–0.3 to BVDD + 0.3
V
Analog input voltage to GND
–0.3 to AVDD + 0.3
V
Input current, continuous
±20
mA
Input current, momentary
±100
mA
Operating temperature range
–40 to +105
°C
Storage temperature range
–65 to +150
°C
+150
°C
Junction temperature range (TJ max)
(TJ max – TA) / θJA
W
Thermal impedance, θJC
15
°C/W
Thermal impedance, θJA
60
°C/W
Power dissipation
Lead temperature (soldering)
Vapor phase (60s)
+215
°C
Lead temperature (soldering)
Infrared (15s)
+220
°C
(1)
2
Stresses above those listed under absolute maximum ratings may cause permanent damage to the device. Exposure to absolute
maximum conditions for extended periods may affect device reliability.
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ELECTRICAL CHARACTERISTICS: +5 V
At –40°C to +85°C, AVDD = 5 V, DVDD = 5 V, BVDD = 3 V to 5 V, using external 2.5-V reference (unless otherwise noted).
AMC7823
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC ANALOG INPUTS
Input voltage range
0
2 × VREF
V
Input impedance
5
MΩ
Input capacitance
15
pF
Input leakage current
±1
µA
ANALOG-TO-DIGITAL CONVERTER
Resolution
12
Bits
Integral linearity
±1
LSB (1)
Differential linearity
±1
LSB
Offset error
±2
LSB
No missing codes
12
Bits
Offset error drift
±4
Offset error match
0.5
Gain error
ppmFS/°C
1
LSB
±6
LSB
Gain error match
0.3
Noise
70
µVRMS
70
dB
Power-supply rejection
AVDD = 5 V ±5%
Throughput rate
1
LSB
200
kHz
Total conversion time
Scan Channels 0 through 7
45
µs
Total conversion time including temperature
Scan Channels 0 through 8
56
µs
Channel-to-channel isolation
VIN = 5 VPP at 10 kHz
0.5
LSB
DIGITAL-TO-ANALOG CONVERTER (2)
Output voltage range
Programmable
Output current
Refer to Typical Characteristics
0
2 × VREF
±1
Resolution
Integral linearity (3)
±2
Monotonicity
Offset error
12
Bits
±8
LSB
12
Differential linearity
Output range = 0 to VREF
Output range = 0 to 2 x VREF
Offset error drift
V
mA
Bits
±0.2
±1
LSB
±0.5
±5
mV
±1
±10
±4
Gain error
Output range = 0 to 2 x VREF
Settling time
Step between code 0x400 to 0xC00,
to ±1 LSB
Code change glitch
1 LSB change, in worst case
Overshoot
Step between code 0x400 to 0xC00
200
mV
Crosstalk
Step between code 0x400 to 0xC00
< 0.5
LSB
Signal-to-noise ratio
Sine wave (1 kHz, 5 VPP) generated by
DAC, sampling at 400 kSPS,
RL = 10 kΩ, CL = 100 pF.
74
dB
Output buffer gain = 2
60
nV/√Hz
Output buffer gain = 1
30
nV/√Hz
Output noise voltage density
(1)
(2)
(3)
±0.3
mV
ppmFS/°C
±1.0
%FS
2
µs
20
nV-s
LSB means least significant bit.
DAC is tested with load of 25 kΩ in parallel with 100 pF to ground.
Measured from code 0x008 to 0xFFF.
3
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ELECTRICAL CHARACTERISTICS: +5 V (continued)
At –40°C to +85°C, AVDD = 5 V, DVDD = 5 V, BVDD = 3 V to 5 V, using external 2.5-V reference (unless otherwise noted).
AMC7823
PARAMETER
CONDITIONS
MIN
TYP
MAX
100.0
100.5
UNITS
PRECISION CURRENT SOURCE
Output current range
0.01
Output current accuracy
Iout = 100 µA
Output current drift
Iout = 100 µA
Output impedance
Iout = 100 µA
Compliance voltage of pin
PRECISION_I_OUTPUT
Iout = 10 mA
99.5
3
Power-supply rejection ratio
10
mA
µA
40
ppm/°C
100
MΩ
4.25
V
60
dB
VOLTAGE REFERENCE (VREF)
Internal reference voltage (4)
At 25°C
Internal reference drift
–40°C to 85°C
2.495
Output impedance of pin EXT_REF_IN
as internal reference output
Short-circuit current
2.505
ppm/°C
10
kΩ
1.20
Internal reference selected
Internal reference de-selected
External reference input capacitance
V
±15
µA
250
External reference voltage
External reference input resistance
2.50
2.55
V
10
kΩ
1
MΩ
5
pF
TEMPERATURE SENSOR
Temperature range
Resolution
Accuracy
–40
85
°C
VREF = 2.5 V
3.2
°C
VREF = 1.25 V
1.6
°C
VREF = 2.5 V
±4
°C
±2.0
°C
VREF = 1.25 V
LEVEL OF PIN GALR AND DAV
IOH = 0.7 mA
4
DVDD
V
IOL = 180 µA
0
0.4
V
DIGITAL INPUT/OUTPUT, EXCEPT PIN GALR AND DAV
VIH
BVDD = 5 V, IIH = 5 µA
3.5
BVDD + 0.3
V
VIL
BVDD = 5 V, IIL = –5 µA
0
0.8
V
BVDD = 5 V, IOH = –3 mA
4
BVDD
V
VOH
Logic level
VOL
BVDD = 5 V, OL = 3 mA
0
0.4
V
VIH
BVDD = 3 V, IIH = 5 µA
2.1
BVDD + 0.3
V
VIL
BVDD = 3 V, IIL = –5 µA
0
0.6
V
2.4
BVDD
V
VOH
Logic level
VIL
BVDD = 3 V, IOL = 3 mA
Input capacitance
(4)
4
BVDD = 3 V, IOH = –3 mA
0
0.4
5
V
pF
Bit GREF in AMC Status/Configuration Register determines the internal reference voltage. The internal VREF = 2.5 V when GREF = 1,
and the internal VREF = 1.25 V when GREF = 0 (see AMC Status/Configuration Register for details).
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ELECTRICAL CHARACTERISTICS: +5 V (continued)
At –40°C to +85°C, AVDD = 5 V, DVDD = 5 V, BVDD = 3 V to 5 V, using external 2.5-V reference (unless otherwise noted).
AMC7823
PARAMETER
CONDITIONS
MIN
TYP
MAX
5
UNITS
POWER SUPPLY REQUIREMENTS
Power-supply voltage
AVDD
Specified performance
2.7
5.5
V
DVDD (5)
Specified performance
2.7
5.5
V
(6)
Specified performance
2.7
5.5
V
BVDD
Quiescent current of AVDD
In normal operation,
precision current source = 0, no DAC
load.
15
All power-down
20
mA
1
Quiescent current of DVDD
0.3
mA
Quiescent current of BVDD
0.1
mA
Power dissipation
100
mW
TEMPERATURE RANGE
Specified performance
–40
+85
°C
Storage
–65
+150
°C
(5)
(6)
DVDD must equal AVDD.
BVDD must not be greater than AVDD or DVDD.
5
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ELECTRICAL CHARACTERISTICS: +3 V
At –40°C to +85°C, AVDD, DVDD, BVDD = 3 V, using external 1.25-V reference (unless otherwise noted).
AMC7823
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC ANALOG INPUTS
Input voltage range
0
2 × VREF
V
Input impedance
5
MΩ
Input capacitance
15
pF
Input leakage current
±1
µA
ANALOG-TO-DIGITAL CONVERTER
Resolution
12
Bits
Integral linearity
±1
LSB (1)
Differential linearity
±1
LSB
Offset error
±3
LSB
No missing codes
12
Bits
Offset error drift
±4
Offset error match
0.5
Gain error
ppmFS/°C
1
LSB
±12
LSB
Gain error match
0.3
Noise
70
µVRMS
70
dB
Power-supply rejection
AVDD = 3 V ±5%
Throughput rate
1.5
LSB
200
kHz
Total conversion time
Scan Channels 0 through 7
47
µs
Total conversion time including temperature
Scan Channels 0 through 8
58
µs
Channel-to-channel isolation
VIN = 2.5 VPP at 10 kHz
0.5
LSB
DIGITAL-TO-ANALOG CONVERTER (2)
Output voltage range
Programmable
Output current
Refer to Typical Characteristics
0
2 × VREF
±1
Resolution
Integral linearity (3)
±2
Monotonicity
Offset error
12
Bits
±8
LSB
12
Differential linearity
Output range = 0 to VREF
Output range = 0 to 2 x VREF
Offset error drift
V
mA
Bits
±0.2
±1
LSB
±0.5
±5
mV
±1
±10
±4
Gain error
Output range = 0 to 2 x VREF
Settling time
Step between code 0x400 to 0xC00,
to ±1 LSB
Code change glitch
1 LSB change, in worst case
Overshoot
Step between code 0x400 to 0xC00
200
mV
Crosstalk
Step between code 0x400 to 0xC00
<0.5
LSB
Signal-to-noise ratio
Sine wave (1 kHz, 5 VPP) generated by
DAC, sampling at 400 kSPS,
RL = 10 kΩ, CL = 100 pF
74
dB
Output buffer gain = 2
60
nV/√Hz
Output buffer gain = 1
30
nV/√Hz
Output noise voltage density
(1)
(2)
(3)
6
LSB means least significant bit.
DAC is tested with load of 25 kΩ in parallel with 100 pF to ground.
Measured from code 0x008 to 0xFFF.
±0.2
mV
ppmFS/°C
±1.0
%FS
2
µs
20
nV-s
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ELECTRICAL CHARACTERISTICS: +3 V (continued)
At –40°C to +85°C, AVDD, DVDD, BVDD = 3 V, using external 1.25-V reference (unless otherwise noted).
AMC7823
PARAMETER
CONDITIONS
MIN
TYP
MAX
100.0
100.5
UNITS
PRECISION CURRENT SOURCE
Output current range
0.01
Output current accuracy
Iout = 100 µA
Output current drift
Iout = 100 µA
Output impedance
Iout = 100 µA
Compliance voltage of pin
PRECISION_I_OUTPUT
AVDD = 2.7 V, Iout = 10 mA
99.5
1.9
Power-supply rejection ratio
10
mA
µA
40
ppm/°C
100
MΩ
2
V
60
dB
VOLTAGE REFERENCE (VREF)
Internal reference voltage (4)
At 25°C
Internal reference drift
–40°C to 85°C
1.247
Output impedance of pin EXT_REF_IN
as internal reference output
Short-circuit current
1.25
1.253
ppm/°C
10
kΩ
µA
125
External reference voltage
1.20
External reference input resistance
External reference input capacitance
V
±20
1.28
V
10
kΩ
5
pF
TEMPERATURE SENSOR
Temperature range
–40
Resolution
Accuracy
85
°C
1.6
°C
±2.0
°C
LEVEL OF PIN GALR AND DAV
IOH = 0.3 mA
2.4
DVDD
V
IOL = 125 µA
0
0.4
V
2.1
BVDD + 0.3
V
0
0.6
V
2.4
BVDD
V
DIGITAL INPUT/OUTPUT, EXCEPT PIN GLAR AND DAV
VIH
IIH = 5 µA
VIL
IIL = –5 µA
VOH
Logic level
VOL
IOH = –3 mA
IOL = 3 mA
0
Input capacitance
0.4
5
V
pF
POWER SUPPLY REQUIREMENTS
Power-supply voltage
AVDD
Specified performance
2.70
3.3
V
DVDD
Specified performance
2.70
3.3
V
BVDD (5)
Specified performance
2.70
3.3
V
15
mA
Quiescent current of AVDD
In normal operation
3
10
All power-down
1
mA
Quiescent current of DVDD
0.3
mA
Quiescent current of BVDD
0.1
mA
Power dissipation
60
mW
TEMPERATURE RANGE
Specified performance
–40
+85
°C
Storage
–65
+150
°C
(4)
(5)
Bit GREF in AMC Status/Configuration Register determines the internal reference voltage. GREF must be cleared when AVDD is less
than 5 V and the internal reference is selected (see AMC Status/Configuration Register for details).
BVDD must be not greater than AVDD or DVDD.
7
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
EXT_REF_IN
DAC 4_OUT
DAC 6_OUT
DAC 5_OUT
DAC 7_OUT
RESET
GPIO−0/ALR0
GPIO−1/ALR1
GPIO−2/ALR2
GPIO−3/ALR3
PIN CONFIGURATION
(TOP VIEW)
30 29 28 27 26 25 24 23 22 21
31
20
CH7
SCLK
32
19
CH6
MOSI
33
18
CH5
MISO
34
17
CH4
SS
35
16
AVDD
CONVERT
BVDD
36
15
AGND
DVDD
37
14
CH3
6
7
8
9
SGND
5
DAC 3_OUT
4
DAC 1_OUT
3
DAC 2_OUT
CH0
2
DAC 0_OUT
GPIO−5
11
10
ISET_RESISTOR
CH1
40
1
PRECISION_I_OUTPUT
CH2
12
DAV
13
39
ELDAC
38
GALR
DGND
GPIO−4
TERMINAL FUNCTIONS
TERMINAL
NO.
8
DESCRIPTION
NAME
1
GALR
Global analog input out-of-range alarm. GALR pin goes low (active) when one (or more) of the first
four accessed analog inputs is out of preset range.
2
DAV
Data available indicator. In the direct mode, DAV pin goes low (active) when the conversion finishes.
In Auto-mode, a 2-µs pulse (active low) appears on this pin when conversion cycle finishes (see ADC
Operation and Registers for details). DAV stays high when deactivated.
3
ELDAC
External DAC synchronous load trigger. DACs that have external synchronous load selected are
updated simultaneously by the rising edge of ELDAC.
4
ISET_RESISTOR
The resistor connected from analog supply to this pin sets the current output from the pin
PRECISION_I_OUTPUT.
5
PRECISION_I_OUTPUT
Current output to drive a thermistor.
6
DAC-0_OUT
Output of DAC-0
7
DAC-1_OUT
Output of DAC-1
8
DAC-2_OUT
Output of DAC-2
9
DAC-3_OUT
Output of DAC-3
10
SGND
Analog input signal ground. This pin must connect to the ground of analog input source to minimize
the digital noise.
11
CH0
Analog input channel 0
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TERMINAL FUNCTIONS (continued)
TERMINAL
NO.
DESCRIPTION
NAME
12
CH1
Analog input channel 1
13
CH2
Analog input channel 2
14
CH3
Analog input channel 3
15
AGND
Analog ground
16
AVDD
Analog power supply, +3 V to +5 V. Must be the same value as DVDD.
17
CH4
Analog input channel 4
18
CH5
Analog input channel 5
19
CH6
Analog input channel 6
20
CH7
Analog input channel 7
21
EXT_REF_IN
When external reference connects here, the internal reference is overridden. When internal reference
is selected, this pin works as output of the internal reference (with 10-kΩ output impedance). See
Reference section for details.
22
DAC-4_OUT
Output of DAC-4
23
DAC-5_OUT
Output of DAC-5
24
DAC-6_OUT
Output of DAC-6
25
DAC-7_OUT
Output of DAC-7
26
RESET
Reset input. Logic low on this pin causes the part to perform hardware reset.
27
GPIO-0/ALR0
Multiple function I/O pin. Works as digital I/O or ALR pin of the first analog input.
28
GPIO-1/ALR1
Multiple function I/O pin. Works as digital I/O or ALR pin of the second analog input.
29
GPIO-2/ALR2
Multiple function I/O pin. Works as digital I/O or ALR pin of the third analog input.
30
GPIO-3/ALR3
Multiple function I/O pin. Works as digital I/O or ALR pin of the fourth analog input.
31
CONVERT
External conversion trigger. The rising edge starts sampling and conversion of the ADC when
external trigger mode is selected.
32
SCLK
Serial clock input
33
MOSI
Master out, slave in. Digital data input for the serial interface
34
MISO
Master in, slave out. Digital data output for the serial interface
35
SS
Slave select input (active low). Data is not clocked into MOSI unless SS is low. When SS is high,
MISO is in high-impedance status.
36
BVDD
Interface power supply. Connects to 3 V for 3-V logic; connects to 5 V for 5-V logic.
37
DVDD
Digital power supply (+3 V to +5 V). Must be the same value as AVDD.
38
DGND
Digital ground
39
GPIO4
General-purpose digital I/O pin
40
GPIO5
General-purpose digital I/O pin
9
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TIMING CHARACTERISTICS: +5 V
At –40°C to +85°C, AVDD = DVDD = 5 V (unless otherwise noted).
PARAMETER
MIN
MAX
UNIT
tsck
SCLK period
42
ns
twsck
SCLK high or low time
21
ns
tLead
SS enable lead time
21
ns
tLag
SS enable lag time
21
ns
ttd
Sequential transfer delay
42
ns
tsu
Data setup time
thi
Data hold time (inputs)
tho
Data hold time (outputs)
tA
Slave access time
21
ns
tdis
Slave MISO disable time
21
ns
tv
Data valid
10
ns
tr
Rise time
30
ns
tf
Fall time
30
ns
tWLDAC
ELDAC width
210
ns
tCONVERT
CONVERT width
210
ns
0
ns
21
ns
0
ns
TIMING CHARACTERISTICS: +3 V
At –40°C to +85°C, AVDD = DVDD = 3 V (unless otherwise noted).
PARAMETER
MIN
MAX
UNIT
tsck
SCLK period
84
ns
twsck
SCLK high or low time
42
ns
tLead
SS enable lead time
42
ns
tLag
SS enable lag time
42
ns
ttd
Sequential transfer delay
84
ns
tsu
Data setup time
0
ns
thi
Data hold time (inputs)
42
ns
tho
Data hold time (outputs)
tA
Slave access time
42
ns
tdis
Slave MISO disable time
42
ns
tv
Data valid
10
ns
tr
Rise time
30
ns
tf
Fall time
30
ns
tWLDAC
ELDAC width
420
ns
tCONVERT
CONVERT width
420
ns
10
0
ns
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
tLag
SS
ttd
tSCK
twsck
tf
tLead
tr
SCLK
twsck
tsu
thi
Command
BIT 15 (MSB)
MOSI Don’t Care
Command
BIT 14 ...1
Command
BIT 0 (LSB)
Don’t Care
READ COMMAND FROM THE HOST
tA
tv
Hi−Z
MISO
tho
DATA OUT
BIT 15 (MSB)
tdis
DATA OUT
BIT 14
DATA OUT
BIT 13 ... 1
Hi−Z
DATA OUT
BIT 0 (LSB)
MISO is in Hi-Z Before Finishing Address Decoding
DATA READ FROM AMC7823 REGISTERS
Note: If SS is High, MISO is in Hi-z
Figure 1. Read Operation (SPI)
tLag
SS
ttd
tsck
tLead
twsck
tf
tr
SCLK
twsck
tsu
MOSI
Don’t Care
thi
Command
Bit 15 (MSB)
Command
Bit 14 . . 1
Command
Bit 0 (LSB)
WRITE COMMAND FROM HOST
MISO
Data In
Bit 15 (MSB)
Data In
Bit 14 . . 1
Data In
Bit 0 (LSB)
Don’t Care
DATA WRITTEN INTO AMC7823 REGISTERS
Hi−Z
tWLDAC
ELDAC
tCONVERT
CONVERT
Figure 2. Write Operation (SPI)
11
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: ANALOG-TO-DIGITAL CONVERTER (ADC)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
DNL (LSB)
0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
0
12
512
512
1024
1536
2048
2560
3072
3584
INL (LSB)
DNL (LSB)
4096
0
512
1024
1536
2048
2560
3072
3584
Code
Code
Figure 3.
Figure 4.
LINEARITY ERROR vs CODE
(+25°C, AVDD = 5V, VREF = 2.5V)
LINEARITY ERROR vs CODE
(+25°C, AVDD = 2.7V, VREF = 1.25V)
1024
1536
2048
2560
3072
3584
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
512
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
DNL (LSB)
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
DNL (LSB)
0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
0
4096
512
1024
1536
2048
2560
3072
3584
Code
Code
Figure 5.
Figure 6.
LINEARITY ERROR vs CODE
(+85°C, AVDD = 5V, VREF = 2.5V)
LINEARITY ERROR vs CODE
(+85°C, AVDD = 2.7V, VREF = 1.25V)
1024
1536
2048
2560
3072
3584
4096
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
LINEARITY ERROR vs CODE
(–40°C, AVDD = 2.7V, VREF = 1.25V)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
DNL (LSB)
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
DNL (LSB)
LINEARITY ERROR vs CODE
(–40°C, AVDD = 5V, VREF = 2.5V)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
0
512
1024
1536
2048
2560
Code
Code
Figure 7.
Figure 8.
3072
3584
4096
4096
4096
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: ANALOG-TO-DIGITAL CONVERTER (ADC) (continued)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
OFFSET ERROR AND OFFSET ERROR MATCH
vs TEMPERATURE
GAIN ERROR AND GAIN ERROR MATCH
vs TEMPERATURE
4.0
AVDD = 5V
VREF = 2.5V
0.8
0.6
0.4
Offset Error
0.2
Offset Error Match
0.0
−0.2
−0.4
−0.6
Delta Error from +25 C (LSB)
Delta Error from +25C (LSB)
1.0
−0.8
2.0
Gain Error
1.0
Gain Error Match
0
−1.0
−2.0
−3.0
−4.0
−1.0
−60
1.0
−40
−20
0
20
40
60
80
−60
100
−20
0
20
40
60
80
Temperature ( C)
Figure 9.
Figure 10.
OFFSET ERROR AND OFFSET ERROR MATCH
vs TEMPERATURE
GAIN ERROR AND GAIN ERROR MATCH
vs TEMPERATURE
AVDD = 2.7V
VREF = 1.25V
3.0
Delta from +25C (LSB)
0.6
0.4
Offset Error Match
Offset Error
0.2
100
4.0
0
−0.2
−0.4
−0.6
2.0
Gain Error
1.0
Gain Error Match
0
−1.0
−2.0
−3.0
−0.8
−4.0
−50
−1.0
−50
−25
0
25
50
75
100
−25
0
25
50
75
Temperature ( C)
Temperature (C)
Figure 11.
Figure 12.
GAIN AND OFFSET ERROR
vs 5V SUPPLY
GAIN AND OFFSET ERROR MATCH
vs 5V SUPPLY
100
1.0
4.0
VREF = 2.5V
VREF = 2.5V
3.0
0.8
Error Match (LSB)
2.0
Error (LSB)
−40
Temperature ( C)
AVDD = 2.7V
VREF = 1.25V
0.8
Delta from +25 C (LSB)
AVDD = 5V
VREF = 2.5V
3.0
1.0
Offset
0
Gain
−1.0
−2.0
0.6
0.4
Gain Match
Offset Match
0.2
−3.0
−4.0
0
4.5
4.75
5.0
5.25
5.5
4.5
4.75
5.0
5V Supply Voltage (V)
5V Supply Voltage (V)
Figure 13.
Figure 14.
5.25
5.5
13
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: ANALOG-TO-DIGITAL CONVERTER (ADC) (continued)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
GAIN AND OFFSET ERROR
vs 3V SUPPLY
GAIN AND OFFSET ERROR MATCH
vs 3V SUPPLY
12.0
1.0
VREF = 1.25V
VREF = 1.25V
8.0
0.8
Error Match (LSB)
Gain
Error (LSB)
4.0
0
Offset
−4.0
Gain Match
0.6
0.4
0.2
−8.0
−12.0
0
2.85
3.0
3.15
3.3
2.7
INTERNAL REFERENCES
vs AVDD VOLTAGE
2.5V AND 1.25V INTERNAL REFERENCES
vs TEMPERATURE
2.5000
1.2500
2.5VREF
2.4998
1.2498
2.4996
1.2496
1.25VREF
2.4994
1.2494
0
−0.5
−1.5
−2.5
−3.0
−3.5
2.4990
1.2490
−4.0
4.5
5.0
2.5VREF
−2.0
1.2492
4.0
1.25VREF
−1.0
2.4992
3.5
AVDD = 5V or 3V
0.5
Delta from +25 C (mV)
1.2502
1.0
−60
5.5
−40
−20
0
20
40
60
80
100
Temperature (C)
AVDD Voltage (V)
Figure 17.
Figure 18.
INTERNAL 2.5V REFERENCE
(AVDD = 5V)
INTERNAL 1.25V REFERENCE
(AVDD = 2.7V)
25
60
50
Frequency (%)
20
15
10
5
40
30
20
10
0
2.505
2.504
2.503
2.502
2.500
2.501
2.499
2.498
2.497
2.496
2.495
0
1.247
1.248
1.249
1.250
1.251
Histogram Bins (V)
Histogram Bins (V)
Figure 19.
14
3.3
Figure 16.
2.5002
Frequency (%)
3.15
Figure 15.
1.2504
3.0
3.0
3V Supply Voltage (V)
2.5004
2.5
2.85
3V Supply Voltage (V)
1.25V Reference (V)
2.7
2.5V Reference (V)
Offset Match
Figure 20.
1.252
1.253
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: DIGITAL-TO-ANALOG CONVERTER (DAC)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
INL (LSB)
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
DNL (LSB)
0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
0
1024
1536
2048
2560
3072
3584
INL (LSB)
DNL (LSB)
0
4096
512
1024
1536
2048
2560
3072
3584
Code
Code
Figure 21.
Figure 22.
LINEARITY ERROR vs CODE
(+25°C, AVDD = 5V, VREF = 2.5V, GAIN = 1)
LINEARITY ERROR vs CODE
(+25°C, AVDD = 2.7V, VREF = 1.25V, GAIN = 1)
512
1024
1536
2048
2560
3072
3584
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
512
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
DNL (LSB)
INL (LSB)
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
DNL (LSB)
0
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
4096
0
512
1024
1536
2048
2560 3072
Code
Figure 23.
Figure 24.
LINEARITY ERROR vs CODE
(+85°C, AVDD = 5V, VREF = 2.5V, GAIN = 1)
LINEARITY ERROR vs CODE
(+85°C, AVDD = 2.7V, VREF = 1.25V, GAIN = 1)
512
1024
1536
2048
2560
3072
3584
4096
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
0
512
1024
1536
2048
2560
Code
Code
Figure 25.
Figure 26.
3072
4096
3584 4096
Code
INL (LSB)
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
−1.0
LINEARITY ERROR vs CODE
(–40°C, AVDD = 2.7V, VREF = 1.25V, GAIN = 1)
DNL (LSB)
INL (LSB)
8.0
6.0
4.0
2.0
0
−2.0
−4.0
−6.0
−8.0
DNL (LSB)
LINEARITY ERROR vs CODE
(–40°C, AVDD = 5V, VREF = 2.5V, GAIN = 1)
3584
4096
15
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: DIGITAL-TO-ANALOG CONVERTER (DAC) (continued)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
NORMALIZED OFFSET ERROR
vs TEMPERATURE
NORMALIZED GAIN ERROR
vs TEMPERATURE
0.10
2.0
Delta from +25 C (%FS)
1.5
Delta from +25 C (mV)
External 2.5V Reference
AVDD = 5V
External 2.5V Reference
AVDD = 5V
1.0
0.5
Gain = +1
0
−0.5
Gain = +2
−1.0
0.05
0
−0.05
−1.5
−2.0
−0.10
−40
−20
0
20
40
60
80
−60
100
0
20
40
60
80
Figure 27.
Figure 28.
VOUT vs
SOURCING AND SINKING CURRENT
VOUT vs
SOURCING AND SINKING CURRENT
6.0
3.0
5.0
2.5
4.0
Sourcing Current
3.0
2.0
Sinking Current
AVDD = 5V
VREF = 2.5V
Gain = +2
100
2.0
Sourcing Current
1.5
1.0
Sinking Current
AVDD = 2.7V
VREF = 1.25V
Gain = +2
0.5
0
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
12
14
16
Sourcing or Sinking Current (mA)
Sourcing or Sinking Current (mA)
Figure 29.
Figure 30.
DAC SETTLING TIME
(GAIN = +2)
DAC SETTLING TIME
(GAIN = +1)
CL = 10pF
RL= 10kΩ
VREF = 2.5V
Code 3932
Input
Code 256
Settling
Detail
Time (1µs/div)
Figure 31.
Input (1V/div)
2
Settling Detail (1LSB/div)
0
18
CL = 10pF
RL= 10kΩ
VREF = 2.5V
Code 4095
Input
Code 512
Settling
Detail
Time (1µs/div)
Figure 32.
20
Settling Detail (1LSB/div)
0
Input (2V/div)
−20
Temperature ( C)
1.0
16
−40
Temperature (C)
Output Voltage (V)
Output Voltage (V)
−60
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: DIGITAL-TO-ANALOG CONVERTER (DAC) (continued)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
DAC POWER-ON RESET
TO 0V
5V
Input (1V/div)
Output (10mV/div)
AVDD, DVDD,
BVDD, RESET
0V
DAC Output
0V
Time (100µs/div)
Figure 33.
TYPICAL CHARACTERISTICS: PRECISION CURRENT SOURCE
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
100µA CURRENT SOURCE
vs TEMPERATURE
PRECISION_I_OUTPUT vs
COMPLIANCE VOLTAGE
0.5
AVDD / VREF = 5V / 2.5V
or 3V / 1.25V
0.3
Delta from Nominal (%)
Delta from +25C (µA)
0.4
0.2
0.1
0
−0.1
−0.2
−0.3
−0.4
−0.5
−50
−25
0
25
50
75
100
0.1
0
−0.1
−0.2
−0.3
−0.4
−0.5
−0.6
−0.7
−0.8
−0.9
−1.0
−1.1
−1.2
4.00
AVDD = 5V
VREF = 2.5V
10µA (nom)
10mA (nom)
1mA (nom)
4.25
100µA (nom)
4.5
Temperature ( C)
Compliance Voltage (V)
Figure 34.
Figure 35.
4.75
5.0
17
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
TYPICAL CHARACTERISTICS: PRECISION CURRENT SOURCE (continued)
At +25°C, AVDD = DVDD = 5V, unless otherwise noted.
60
10µA (nom)
50
10
100µA (nom)
1mA (nom)
Current (µA)
Figure 36.
Figure 37.
CURRENT SOURCE PRODUCTION DISTRIBUTION
(1.25V EXTERNAL REFERENCE)
70
60
Frequency (%)
50
40
30
20
10
Current (µA)
Figure 38.
18
100.5
100.4
100.2
100.3
100.1
100.0
99.9
99.8
99.7
99.6
99.5
0
100.5
100.4
100.3
100.2
100.1
Compliance Voltage (V)
100.0
2.80
99.9
2.60
2.40
99.8
0
2.20
99.7
2.00
30
20
10mA (nom)
1.80
40
99.6
1.60
70
AVDD = 2.7V
VREF = 1.25V
99.5
0.1
0
−0.1
−0.2
−0.3
−0.4
−0.5
−0.6
−0.7
−0.8
−0.9
−1.0
−1.1
−1.2
CURRENT SOURCE PRODUCTION DISTRIBUTION
(2.5V EXTERNAL REFERENCE)
Frequency (%)
Delta from Nominal (%)
PRECISION_I_OUTPUT vs
COMPLIANCE VOLTAGE
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
APPLICATION INFORMATION
DIGITAL INTERFACE
The AMC7823 communicates through a standard SPI bus. The SPI allows full-duplex, synchronous, serial
communication between a host processor (the master) and peripheral devices (slaves). The SPI master
generates the synchronizing clock and initiates transmissions. SPI slave devices, such as the AMC7823, depend
on a master to start and synchronize transmissions.
A transmission begins when initiated by an SPI master. A word from the master is shifted into the AMC7823
through the MOSI pin under the control of the master serial clock, SCLK. A word from an AMC7823 register is
shifted out from the MISO pin under the control of SCLK as well.
The idle state of the serial clock for the AMC7823 is low, which corresponds to a clock polarity setting of 0
(typical microprocessor SPI control bit CPOL = 0). The AMC7823 interface is designed with a clock phase setting
of 1 (typical microprocessor SPI control bit CPHA = 1). In both the master and slave, the data is shifted out on
the rising edge of SCLK and sampled on the falling edge of SCLK where data is stable. The master begins
driving the MOSI pin on the first rising edge of SCLK after SS is activated (low).
To write data into AMC7823, the host activates the slave select signal (SS = low) and issues a WRITE command
to start the data transmission. The AMC7823 always interprets the first word (from the host) immediately
following the falling edge of SS signal as a command. The data to be written into the AMC7823 follow the
command. The slave select pin (SS) must remain low until all data are transmitted (see Figure 39). Otherwise,
the WRITE operation is terminated. Likewise, to read data from AMC7823, the host activates the slave select
signal and sends a READ command. The AMC7823 then sends data out through the MISO pin under the control
of SCLK. The slave select pin must remain low until all data are shifted out (see Figure 39). Otherwise, the
transmission is terminated, and all remaining data (if any) are ignored.
When the operation is terminated, the master must issue a new command to start a new operation.
All registers in the AMC7823 are 16-bit. It takes 16 clock pulses of SCLK to transfer one data or command word.
All data are transferred into (or out of) the AMC7823 through an internal serial-parallel (parallel-serial) register. If
SS is deactivated (that is, goes high) before the 16th clock finishes, the incomplete transfer is terminated
immediately and the data being transferred are ignored. In a write operation, this data is not written into the
AMC7823 register. In a read operation, the remaining data bits are not shifted out, and the data must be ignored.
AMC7823 COMMUNICATION PROTOCOL
With the exception of two external trigger pins, an external RESET pin, and an external current setting resistor,
the AMC7823 is entirely controlled by registers. Reading from and writing to these registers is accomplished by
issuing a 16-bit command word followed immediately by data for a single register or for a range of registers. This
command word is constructed as shown in the Bit Register. The data word(s) format for the target register(s) are
illustrated in subsequent pages of this document.
Bit Register
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
R/W
X
PG1
PG0
X
SADR4
SADR3
SADR2
SADR1
SADR0
X
EADR4
EADR3
EADR2
EADR1
EADR0
X : Don't Care
Where:
R/W: Data flow direction bit.
R/W = 1. Read operation. Data is transferred from AMC7823 to the host.
R/W = 0. Write operation. Data is transferred from the host to AMC7823.
PG1 – PG0: Memory page of addressed register(s) (see Table 1).
SADR4 – SADR0: Starting address of register(s) on selected page.
EADR4 – EADR0: Ending address of register(s) on selected page.
19
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
NOTE: If the ending address is equal to or smaller than the starting address, only the starting address is
accessed. In this case, the operation applies only to the starting address; all remaining data and memory
locations (if any) are ignored. In this manner, a single register may be addressed by setting [EADR4:EADR0] =
00000 or [SADR4:SADR0] ≥ [EADR4:EADR0].
Table 1. Page Addressing
PG1
PG0
PAGE ADDRESS
0
0
0
0
1
1
1
0
Reserved
1
1
Reserved
For example, to read the register with address 0x00 on page 0, the host processor must send the AMC7823 the
command 0x8000; this command specifies a read operation on page 0, address 0. After sending the command,
the host reads one data word. To read the registers 0x02 to 0x07 on page 0 (ADC Data-2 to ADC Data-7), the
host must send 0x8087 first, and then clock six data words sequentially out of the AMC7823. The first data word
is from 0x02, the second from 0x03, and the sixth from 0x07. If the host continues clocking data out after reading
the last location [EADR4:EADR0], the value 0x0000 is output until the operation stops. However, if the host
deactivates SS before reading the last register, the operation is terminated and all remaining registers are
ignored.
Likewise, to load data into the registers with addresses 0x03 to 0x05 on page 1 (DAC-3 Data Register to DAC-5
Data Register), the host sends command 0x10C5 followed sequentially by three data words. The first word is
written into 0x03 of page 1, the second goes to 0x04, and the third goes to 0x05. If the host continues to transfer
data into AMC7823 after writing the last location [EADR4:EADR0], all these data are ignored until the operation
stops. However, if the host deactivates SS before writing the last location, the operation is terminated and all
remaining locations are ignored.
See the AMC7823 Memory Map (Table 2) for details of register locations.
Figure 39 shows an example of a complete data transaction between the host processor and the AMC7823.
SS
SCLK
MOSI
Write Command
1st Data [SADR4:SADR0]
Last Data [EADR4:EADR0]
Data Written into AMC7823 Registers
SS
SCLK
MOSI
MISO
Read Command
Hi−Z
Don’t Care
1st Data [SADR4:SADR0]
Last Data [EADR4:EADR0]
Data Read from AMC7823 Registers
Figure 39. Write and Read Operation of AMC7823 Interface
20
Hi−Z
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
AMC7823 MEMORY MAP
The AMC7823 has several 16-bit registers separated into two pages of memory, Page 0 and Page 1. The
memory map is shown in Table 2. Locations that are marked Reserved read back 0x0000 if they are read by the
host. Writing to these locations has no effect. Figure 40 explains the Read/Write operation.
Table 2. AMC7823 Memory Map
Page 0: Data/Status Registers
Address
R/W
Default
00
R
0x0000
01
R
02
R
03
Register Name
Page 1: Control/Setting Registers
Address
R/W
Default
ADC-0 Data
00
R/W
0x0000
DAC-0 Data
Register Name
0x0000
ADC-1 Data
01
R/W
0x0000
DAC-1 Data
0x0000
ADC-2 Data
02
R/W
0x0000
DAC-2 Data
R
0x0000
ADC-3 Data
03
R/W
0x0000
DAC-3 Data
04
R
0x0000
ADC-4 Data
04
R/W
0x0000
DAC-4 Data
05
R
0x0000
ADC-5 Data
05
R/W
0x0000
DAC-5 Data
06
R
0x0000
ADC-6 Data
06
R/W
0x0000
DAC-6 Data
07
R
0x0000
ADC-7 Data
07
R/W
0x0000
DAC-7 Data
08
R
0x0000
ADC-8 Data
08
R/W
0x0000
LOAD DAC
09
R
0x0000
ALR Register
09
R/W
0x0000
DAC Configuration
0A
R/W
0xFFFF
GPIO Register
0A
R/W
0x4000
AMC Status/Configuration
0B
Reserved
0B
R/W
0x0000
ADC Control
0C
Reserved
0C
R/W
0x0000
RESET
0D
Reserved
0D
R/W
0x0000
Power-Down
0E
Reserved
0E
R/W
0x0FFF
Threshold-Hi-0
0F
Reserved
0F
R/W
0x0000
Threshold-Low-0
10
Reserved
10
R/W
0x0FFF
Threshold-Hi-1
11
Reserved
11
R/W
0x0000
Threshold-Low-1
12
Reserved
12
R/W
0x0FFF
Threshold-Hi-2
13
Reserved
13
R/W
0x0000
Threshold-Low-2
14
Reserved
14
R/W
0x0FFF
Threshold-Hi-3
15
Reserved
15
R/W
0x0000
Threshold-Low-3
16
Reserved
16
Reserved
17
Reserved
17
Reserved
18
Reserved
18
Reserved
19
Reserved
19
Reserved
1A
Reserved
1A
Reserved
1B
Reserved
1B
Reserved
1C
Reserved
1C
Reserved
1D
Reserved
1D
1E
Reserved
1E
1F
Reserved
1F
Reserved
R
0x4000
Part Revision Number
Reserved
21
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
RECEIVING
COMMAND
READ OPERATION
(1)
[ADR] = [SADR]
Yes
WRITE OPERATION
No
READ ?
[ADR] = [SADR]
READ DATA
WRITE DATA
[ADR] + 1
[ADR] + 1
(1)
(3)
(3)
Yes
Is SS deactivated?
Yes
Is SS deactivated?
No
No
(2)
(2)
No
[ADR] > [EADR]
[ADR] > [EADR]
No
Yes
Send
Output
0x0000
Ignore any
remaining data
Waiting for new
command
(1)
[SADR] represents the start address, which is specified by bits [PG1:PG0] and [SADR4:SADR0] in the command
word. [ADR] represents the current address.
(2)
[EADR] represents the end address, which is specified by bits [PG0:PG1] and [EADR4:EADR0] in the command
word.
(3)
Host ends data transfer by deactivating SS.
Figure 40. READ/WRITE Operation
22
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ADC OPERATION (See AMC Status/Configuration Register and ADC Control Register)
Out-of-Range Alarm of
first four inputs being
converted
Out-of-Range
ALARM
Double-Buffered
ADC Data Register
To Shifter
Register
ADC−0
DATA
ADC−0
TMPRY
MUX
CH0
External trigger works in Direct-Mode only.
CH3
After conversion of CH-n finished,
ADC-n TMPRY register is updated
immediately.
TMPRY register is a temporary register
.
All ADC-n DA TA registers are
updated simultaneously when the
conversion of the last channel
selected is completed. (1)
To Shift
Register
CMOD of ADC Control Register defines
conversion mode.
For Direct-Mode (CMOD = 0), each channel
being converted is accessed one time after
triggered.
For Auto-Mode (CMOD = 1), all channels
being converted are accessed repeatedly
after triggered.
ADC
CH7
CH8
(temperature)
Bit GREF, effective for
Internal Reference only (2)
ADC−6
ADC−6
DATA
TMPRY
Internal Trigger generated by
Writing ADC Control Register
0
ADC−7
DATA
ADC−7
TMPRY
ADC−8
DATA
ADC−8
TMPRY
1
CONVERT, External
Bit ECNVT
Bit DAVF, Pin DAV
Bit ECNVT of AMC Status and Configuration Register
selects the trigger signal.
ECNVT = 1, Rising Edge of External CONVERT triggers ADC
ECNVT = 0, Writing ADC Control Register triggers ADC
Bit DAVF and Pin DAV indicate new data available.
After ADC-n Data are Updated, DAVF is set to ‘1’.
Pin DAV Goes Low (Direct-Mode) or Sends 2 ms
Pulse (Auto-Mode). Refer to Figure 42, Figure 43 and
Figure 44.
(1)
To avoid conflict, the data is not loaded into ADC-n data register from ADC-n temporary register until the data transfer
from the ADC-n data register to the shift register (if any) finishes.
(2)
When the internal reference is selected, the bit GREF determines the input range: GREF = 0, 0 to 2.5 V; GREF = 1, 0
to 5 V (for 5-V supply only). When an external reference is selected, the input range is 0 to 2 × VREF. The input
cannot be above AVDD.
Figure 41. ADC Structure
The ADC has nine analog inputs. Channels CH0 through CH7 receive external analog inputs. CH8 is dedicated
to the on-chip temperature sensor (see On-chip Temperature Sensor section).
ADC Trigger Signals (see AMC Status/Configuration Register)
The ADC can be triggered externally (external trigger mode) or internally (internal trigger mode). Bit ECNVT
(Enable CONVERT) of the AMC Status/Configuration Register determines which mode is used. When ECNVT is
set to '1', the ADC works in external trigger mode and the rising edge of the external signal CONVERT initiates
data conversion. When ECNVT is cleared to '0', the ADC is in internal trigger mode, and writing to the ADC
Control Register initiates conversion.
After the ADC is triggered, a group of analog inputs (up to nine channels may be specified) are multiplexed and
each channel is converted. The starting and ending addresses of the group of channels are specified by the bits
[SA3:SA0] and [EA3:EA0], respectively, in the ADC Control Register (see ADC Control Register for details). The
specified channels are converted sequentially from the starting to ending address, according to Table 12, the
Analog Input Channel Address Map. If the ending address is equal to or smaller than the starting address, only
the starting address channel is converted.
23
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
Conversion Mode
When internal trigger mode is selected (ECNVT = 0), two types of ADC conversion are available: direct-mode
and auto-mode. The bit CMODE (Conversion MODE) of the ADC Control Register specifies the conversion
mode. When external trigger mode is selected (ECNVT = 1), only direct-mode conversion is available. In this
case, bit CMODE in the ADC Control Register is ignored. (See Table 3.)
In direct-mode, each analog channel within the specified group is converted a single time. After the last channel
is converted, the ADC goes into idle state and waits for a new trigger. Only the starting channel is converted if
the ending address is equal to or smaller than the starting address.
Auto-mode is a continuous operation. In auto-mode, each analog channel within the specified group is converted
sequentially from [SA3:SA0] to [EA3:EA0] and repeatedly until one of the following events occur:
• a new internal trigger is issued;
• the conversion mode is changed to direct-mode by rewriting the ADC Control Register; or
• the external trigger is enabled by rewriting the AMC Status/Configuration Register.
When a new internal trigger is issued, a new conversion process starts. If the ending address [EA3:EA0] is equal
to or smaller than the starting address [SA3:SA0], the starting address channel is repeatedly converted and
others are ignored.
Table 3 summarizes the ADC conversion modes.
Table 3. ADC Conversion Mode
ECNVT OF AMC STATUS/
CONFIGURATION REGISTER
CMODE OF
ADC CONTROL REGISTER
1
–
External Trigger, Direct-Mode
0
0
Internal Trigger, Direct-Mode
0
1
Internal Trigger Auto-Mode
ADC CONVERSION MODE
Double-Buffered ADC Data Register
The host can access all nine double-buffered ADC Data registers. The conversion result from the analog input
with the channel address n is stored in the ADC-n Data register. When the conversion of an individual channel is
completed, the data is immediately transferred into the corresponding ADC-n temporary (TMPRY) register, the
first stage of the data buffer. When the conversion of the last channel ( [EA3:EA0] ) finishes, all data in ADC-n
TMPRY registers are transferred simultaneously into the corresponding ADC-n Data registers, the second stage
of the data buffer. However, if a data transfer is in progress between an ADC-n Data Register and the AMC Shift
Register, this ADC-n Data Register is not updated until the data transfer is complete. The conversion result from
channel address n is stored in the ADC-n Data Register. For example, the result from channel [0x04] is stored in
the ADC-4 Data Register, and the result from channel [0x07] is stored in the ADC-7 Data Register. The ADC-8
Data Register is used to store on-chip temperature measurement data (see the On-chip Temperature Sensor).
SCLK Clock Noise
The host activates the slave select signal SS (low) to access the AMC7823. When SS is high, the SCLK clock is
blocked. To avoid noise caused by SCLK clock, deactivate SS (high) for at least the conversion process time
immediately after the ADC conversion starts.
Handshaking with the Host (see AMC Status/Configuration Register)
The DAV pin and the bit DAVF (Data Available Flag) of the AMC Status/Configuration Register provide
handshaking with the host. Pin and bit status depend on the conversion mode (direct or auto). In direct-mode,
after ADC-n Data registers of all of the selected channels are updated, the DAVF bit in the AMC
Status/Configuration Register is set immediately to '1', and the DAV pin is active (low) to signify new data is
available. Reading the ADC-n Data Register or re-starting the ADC clears bit DAVF to '0' and deactivates DAV
pin (high).
In auto-mode, after ADC-n Data registers of the selected channels are updated, a pulse of 2 µs (low) appears on
pin DAV to signify new data is available. However, bit DAVF is always cleared to '0' in auto-mode.
Figure 42, Figure 43 and Figure 44 illustrate the handshaking protocol.
24
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
SS
SS
WRITE ADC
CONTROL Register
WRITE ADC
Internal
CONTROL Register 2nd
Trigger
1st Internal
Trigger
WRITE ADC
CONTROL Register
MOSI
Internal Trigger
MOSI
DAV
2ms
DAV
1st Conversions,
[SA3:SA0] to [EA3:EA0]
2nd Conversions,
[SA3:SA0] to [EA3:EA0]
1st Round of
2nd Round of
Conversions,
Conversions,
[SA3:SA0] to [EA3:EA0] [SA3:SA0] to [EA3:EA0]
Figure 42. Internal Trigger, Direct-Mode
Figure 43. Internal Trigger, Auto-Mode
Rising Edge
Starts Conversions
1st Trigger
2nd Trigger
3rd Trigger
CONVERT
DAV
1st Conversions, of
Analog Inputs, From
[SA3:SA0] to [EA3:EA0]
2nd Conversions,
[SA3:SA0] to [EA3:EA0]
3rd Conversions,
[SA3:SA0] to [EA3:EA0]
Figure 44. External Trigger
Analog Input Out-of-Range Detection (see Analog Input Out-of-Range Alarm Section)
The first four analog inputs of the group defined by the bits [SA3:SA0] and [EA3:EA0] are implemented with
out-of-range detection. When an input is out of the preset range, the corresponding alarm flag, bit ALR-n of the
ALR (Alarm) Register is set. If any of the four inputs are out of range, the global out-of-range pin GALR goes low.
Four GPIO pins (GPIO-0, GPIO-1, GPIO-2 and GPIO-3) can be configured as out-of-range indicators for each of
the first four analog inputs. See the Analog Input Out-of-Range Alarm and Digital I/O sections for more details.
Full-Scale Range of Analog Input
The full-scale range of the analog input is 2 × VREF, but must not exceed the supply value AVDD. Input saturation
can occur if the analog input exceeds this value.
The internal reference or an externally applied reference may be used as VREF. The bit SREF in the AMC
Status/Configuration Register controls the selection of the internal reference. When SREF = 0 (power-up default
condition), the internal reference is selected and is internally applied through a 10-kΩ resistor to pin 21. When
SREF = 1, the internal reference is disconnected from pin 21, and an external reference may be applied. See
Figure 48.
Table 4 shows the configuration of the ADC input range.
Table 4. Configuration of ADC Input Range
BIT
GREF
BIT
SREF
ADC INPUT
RANGE
0
0
0 to 2.5 V
1
0
0 to 5 V
Don't
care
1
0 to 2 × VREF
DESCRIPTION
Internal reference, 1.25 V
Internal reference, 2.5 V, AVDD = 5 V only
External reference VREF. 2 × VREF must not be greater than AVDD.
Set SREF = 1 when applying external reference.
25
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
The bit GREF in the AMC Status/Configuration Register selects between two preset internal reference values.
When GREF = 0 (power-up default condition), the internal reference is set to 1.25 V. When GREF = 1, the
internal reference is 2.5 V. GREF must be cleared to '0' when the power supply is less than 5 V.
When an external reference is applied, the input range is 0 to 2 × VREF, and is not affected by the bit GREF. In
this case, ideally SREF has been set to '1' and the internal reference is disconnected. This condition is preferred
for operating the AMC7823. If SREF = 0, the external reference overrides the internal reference, provided it can
accommodate a 10-kΩ load. To avoid input saturation, the external reference must not be greater than 2.5 V
when the analog power supply is 5 V, and must not be greater than 1.25 V when the supply is 3 V.
Figure 45 illustrates the ADC operation.
New ADC Conversion Trigger
Clear DAVF bit in AMC
Status/Configuration Register
Clear all ALR-n in ALR Register
(1)
Set [ADR] = [SA]
Sample
Convert
Update ADC-n TMPRY Register
No
First four channels?
Yes
(2)
Out-of-range?
Yes
Drive GALR Pin Low
Set ALR-n Bit in ALR Register
No
[ADR] + 1
(1)
No
[ADR] > [EA] ?
Yes
Update ADC-n
Data Register
Auto-Mode,
Internal Trigger only
(4)
Auto-Mode
Yes
Apply 2-ms Pulse (Low)
to Pin DAV
No
(3)
Direct-Mode
Set DAVF bit;
Drive DAV Pin Low
ADC in idle
Waiting new trigger
(1)
[SA] represents the first input channel, [EA] represents the last input channel. [ADR] represents the current input
channel. [SA3:SA0] is the address of [SA]. [EA3:EA0] is the address of [EA].
(2)
GALR pin goes high and bits ALR-n are cleared after new ADC Conversion trigger.
(3)
After reading the ADC Data Register, bit DAVF is cleared, and the DAV pin goes high.
(4)
In Auto-mode, bit DAVF is always cleared.
Figure 45. ADC Operation Flow Chart
26
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ON-CHIP TEMPERATURE SENSOR
The AMC7823 has an integrated temperature sensor to measure the on-chip temperature. This measurement
relies on the characteristics of a semiconductor p-n junction operating at a known current level. The forward
voltage of the diode (VBE) depends on the current passing through it and the junction temperature.
Diode Temperature
Sensor
SW2
I2 (10 mA)
CH8 (TEMP)
MUX
Channel CH8 is dedicated to the on-chip temperature sensor. When CH8 is converted, the on-chip temperature
measurement process is activated. Two measurements, and therefore two ADC conversions, are required to
capture the temperature data. First, the diode is driven by current I1 (750 µA) and the forward voltage VBE1 is
measured. Next, the diode is driven by current I2 (10 µA) and VBE2 is measured. The difference of these two
voltages, ∆VBE, is stored in the ADC-8 Data Register as straight binary code. See Figure 46.
ADC
SW1
I1 (750 mA)
NOTE: When CH8 is converted, two conversions are performed. During the first conversion, SW1 is turned on, SW2 is off,
and the diode is driven by I1 (750 µA). During the second conversion, SW2 is turned on, SW1 is off, and the diode is
driven by I2 (10 µA).
Figure 46. Local Temperature Sensor Operation
In direct-mode operation, the temperature can be measured by converting Channel CH8 only, or by converting
several channels including Channel CH8. In auto-mode, the temperature must be measured by converting at
least two channels including Channel CH8.
The following equations illustrate the corresponding temperature calculation process:
∆VBE (mV) = decimal code (convert from ADC-8 Data Register binary code) × 1.22 mV for VREF = 2.5 V
or
∆VBE (mV) = decimal code (convert from ADC-8 Data Register binary code) × 0.61 mV for VREF = 1.25 V.
Temp (°K) = 2.6 × ∆VBE (mV)
or
Temp (°C) = 2.6 × ∆VBE (mV) – 273°K.
The resolution of this calculation is 3.2°C/LSB when the reference voltage is 2.5 V and 1.6°C/LSB for a reference
voltage of 1.25 V.
27
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
DAC OPERATION (see DAC-n Data Registers and DAC Configuration Register)
AMC7823 has eight double-buffered DACs. The outputs of the DACs can be updated synchronously or
individually (asynchronously). Figure 47 illustrates the generic DAC structure.
Data to Host
when Read
Data from
Host
DAC-0
VOUT Range: 0 - VREF x Gain
DAC-0
Latch
DAC-0
Data
VOUT0
Bit SLDA-n of DAC Configuration Register determines
when DAC-n Latch is loaded with the value of
DAC-n Data Register.
SLDA-n = 1: Latch is loaded when Synchronous
Loading signal occurs; synchronous loading
SLDA-n = 0: Latch is loaded immediately after
DAC-n Data register is written; asynchronous loading
Bit PDAC-0
(Power-Down bit in Power-Down
Register; see (1) )
5 kW
Gain = 2 if GDAC-0 = 1
Gain = 1 if GDAC-0 = 0
Bit GDAC-0
(DAC Configuration Register)
DAC-7
DAC-7
Data
BB00h
Load DAC
Register
Bit PDAC-7 (Power-Down bit
in Power-Down Register)
Internal ILDAC
Synchronous
Loading Signal
Bit GDAC−7
External ELDAC
Loads all DAC-n latches when corresponding SLDA-n is set to ‘1’.
Does not affect DAC-n when SLDA-n is cleared to ‘0’.
(1)
When PDAC-n = 0, DAC-n is in power-down mode; the output buffer of DAC-n connects to ground through a 5-kΩ
load.
Figure 47. DAC Structure
Double-Buffered Data Register
All eight DAC data registers are double-buffered. Each DAC has an internal latch preceded by an input register.
Data is initially written to an individual DAC-n Data register and then transferred to its corresponding DAC-n
Latch. When the DAC-n Latch is updated, the output of DAC-n changes to the newly set value. When the host
reads the register memory map location labeled DAC-n Data, the value held in the DAC-n Latch is returned (not
the value held in the input DAC-n Data Register).
Synchronous Load, Asynchronous Load, and Output Updating
The DAC latches can be updated synchronously or asynchronously. The bit SLDA-n (Synchronous Load) of the
DAC Configuration Register is used to specify the DAC updating mode.
Asynchronous mode is active when SLDA-n is cleared to '0'. Immediately after writing to the DAC-n Data
Register, its data is transferred to the corresponding DAC-n Latch Register, and the output of DAC-n changes
accordingly.
Synchronous mode is selected when the bit SLDA-n is set to '1'. The value of the DAC-n Data Register is
transferred to the DAC-n Latch only after an active DAC synchronous loading signal occurs, which immediately
updates the DAC-n output. Under synchronous loading operation, writing data into a DAC-n Data Register
changes only the value in that register, but not the content of DAC-n Latch nor the output of DAC-n, until the
synchronous load signal occurs.
28
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
The DAC synchronous load signal can be the rising edge of the external signal ELDAC, or the internal signal
ILDAC. Write BB00h into the Load DAC Register to generate ILDAC. When the DAC synchronous load signal
occurs, all DACs with the bit SLDA-n set to '1' are updated simultaneously with the value of the corresponding
DAC-n Data register. By setting the bit SLDA-n properly, several DACs can be updated at the same time. For
example, to update DAC0 and DAC1 synchronously, the host sets the bits SLDA-0 and SLDA-1 to '1' first, then
writes the proper values into the DAC-0 Data and DAC-1 Data registers, respectively. After this presetting, the
host activates ELDAC (or ILDAC) to load DAC0 and DAC1 simultaneously. The outputs of DAC0 and DAC1
change at the same time.
Table 5 summarizes methods to update the output of DAC-n.
Table 5. DAC-n Output Update Summary
BIT SLDA-n
WRITING LOAD
DAC REGISTER
EXTERNAL
ELDAC SIGNAL
0
Don't care
Don't care
OPERATION
Update DAC-n individually.
DAC-n Latch and DAC-n Output are immediately updated after writing to DAC-n
Data Register
1
Write 0xBB00
0
Simultaneously update all DAC by internal trigger .
Writing 0xBB00 generates internal load DAC trigger signal ILDAC, which causes
DAC-n Latches and DAC-n Outputs to be updated with the contents of
corresponding DAC-n Data Register.
1
No
Rising edge
Simultaneously update all DACs by external trigger ELDAC.
Rising edge of ELDAC causes DAC-n Latches and DAC-n Outputs to be
updated with the contents of corresponding DAC-n Data Register.
Full-Scale Output Range
Full-scale output range of each DAC is set by the product of the value of the reference voltage times the gain of
the DAC output buffer, VREF × Gain. The bit GDAC-n (Gain of DAC-n output buffer) of the DAC Configuration
Register sets the gain of the individual DAC-n output buffer. The gain is unity (1) when GDAC-n is cleared to '0',
and is 2 when GDAC-n is set to '1'.
The value of VREF may be controlled by bits SREF and GREF in the AMC Status/Configuration Register and by
the choice of internal or external reference. For a similar description, see the Full-Scale Range of Analog Input in
the ADC Operation section.
Full-scale output range of each DAC is limited by the analog power supply because the DAC output buffer
cannot exceed AVDD. Table 6 shows how to configure the DAC output range.
Table 6. Configuration of DAC Output Range
OUTPUT RANGE
SREF
GREF
GDAC-n
REFERENCE
AVDD = 3 V
AVDD = 5 V
0
0
0
Internal 1.25 V
0 V to 1.25 V
0 V to 1.25 V
0
0
1
Internal 1.25 V
0 V to 2.5 V
0 V to 2.5 V
0
1
0
Internal 2.5 V
0 V to 2.5 V
0 V to 2.5 V
0
1
1
Internal 2.5 V
Saturated at 3 V
0 V to 5 V
1
Don't
care
0
External VREF
0 V to External VREF,
External VREF ≤ AVDD
0 V to External VREF,
External VREF ≤ AVDD
1
Don't
care
1
External VREF
0 V to External VREF × 2
2 × External VREF ≤ AVDD
0 V to External VREF × 2
2 × External VREF ≤ AVDD
29
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
After power-on or reset, all DAC-n Data Registers and all DAC-n Latches are cleared to '0'. This clearing process
results in all DAC outputs at 0 V, gain of unity, and a full-scale output range preset to either 1.25 V or equal to
the external reference (if it is applied) because bits SREF and GREF are also cleared to '0'.
Zero Code Output Value
Each DAC buffer is clamped to prevent the output from going to 0 V. Thus, when the input code is 000h, the
output is typically 15 mV to 20 mV. This output keeps the closed-loop DAC output buffer in an active, stable
operating regime, allowing it to immediately respond to an input that produces an output typically greater than
20 mV. Near-zero-volt output for a particular DAC-n may be achieved by clearing bit PDAC-n to '0' in the
Power-Down register.
POWER-DOWN MODE
The AMC7823 is implemented with power-down mode. Bits in the Power-Down Register control power applied to
the ADC, each DAC output buffer, the output amplifier of the precision current source, and the reference buffer.
The reference buffer drives all the DAC resistor strings and supplies reference voltage to the precision current
source. After power-on reset or any forced hardware or software reset, the Power-Down Register is cleared, and
all these specified components are in power-down mode.
In power-down mode, most of the linear circuitry is shut down. The ADC halts conversions, output current of the
precision current source drops to zero, and each external DAC output pin is switched from the DAC output buffer
to analog ground through an internal 5-kΩ resistor. The internal reference and the internal oscillator remain
powered to facilitate rapid recovery from power-down mode.
None of the bits in the Power-Down Register affect the digital logic. All digital signals (such as the SPI interface,
RESET, ELDAC, ALR, and all GPIO) still work normally in any power-down condition. In power-down mode, the
host can read registers to get information, or write to registers to change settings. No write operation can start
the ADC (if the ADC is in power-down), or change the DAC output (if the DAC is in power-down), but write
operations can update register values. The new register values are effective immediately upon exiting the
power-down mode. In this way, the host can preset DACs and the ADC before a wake-up call.
The contents of all Page 1 addresses (see Table 2) do not change when entering or exiting power-down mode.
The contents of the ADC registers and the alarm information in the ALR and GPIO Registers of Page 0 do not
change when entering or exiting power-down mode if the ADC is in direct mode before powering down. To
avoid losing ADC register content and alarm information in the ALR and GPIO Registers while the ADC is
powered down, do not issue a convert command during power-down mode. General-purpose I/O data are not
affected. For details, see the sections on the ALR Register and the GPIO Register.
For power-down mode details, see the Power-Down Register section.
30
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
REFERENCE
The AMC7823 requires a reference voltage to drive the ADC, the DACs, and the precision current source. It can
accommodate the application of an external reference voltage, or it can supply reference from an internal
bandgap voltage circuit as shown in Figure 48. Pin 21, EXT_REF_IN, is common to either source. An internal
10-kΩ resistor connects the internal reference source to pin 21. This pin provides a point for noise filtering by
placing a capacitor, if desired, from the pin to analog ground. The time constant of this filter is [ (10 kΩ) ×
(CFILTER) ]. The resistor also allows an external reference applied to pin 21 to override the internal reference,
provided it can drive the 10-kΩ load.
C Filter
21
1.25 V
10 kW
Bandgap
Reference
A1
2.5 V
Bit
GREF = 0
Bit
SREF = 1
(Refer to diagram
of Current Source,
Figure 49)
To DACs
Buffer and
Controller
A2
To Precision
Current Source
To ADC
Figure 48. Reference
Logic bits SREF and GREF of the AMC Status/Configuration Register specify operation of the internal reference
and also should be considered when applying an external reference, as explained below. These bits also provide
information to the precision current source and are used in configuring that source (refer to the Precision Current
Source section for details).
When SREF is cleared to '0' (the default or power-on reset condition), the internal reference is selected and
connected to pin 21 by the 10-kΩ resistor. When SREF is set to '1', the internal reference is de-selected and
disconnected from pin 21. Pin 21 then floats unless an external reference is applied.
The bit GREF selects one of two pre-set values for the internal reference voltage. When GREF is cleared to '0',
the internal reference voltage is +1.25 V. When GREF is set to '1', the internal reference voltage is +2.5 V.
It is recommended to always set SREF to '1' when using an external source; otherwise, the external reference
must sink or source a current of value equal to the difference in the reference voltages divided by 10 kΩ. For
example, if SREF and GREF are both cleared to '0' and a 2.5-V external reference is applied, the AMC7823
must unnecessarily sink 125 µA.
31
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
PRECISION CURRENT SOURCE
The AMC7823 provides the user with a precision current source for driving an external component such as a
thermistor. Output current from pin 5 is set by the value of the resistor (RSET) connected from pin 4 to the analog
supply voltage. This resistor should be close to the AMC7823 to minimize any voltage drop from the analog
supply to the resistor. Internal closed-loop circuitry impresses a fixed voltage across the set resistor by means of
an operational amplifier and a PMOS-follower output driver. Current through the set resistor supplies the follower.
The follower driver supplies this current to the external load connected from PRECISION_I_OUTPUT (pin 5) to
ground. This circuit architecture maintains high output impedance and provides wide output voltage compliance.
See Figure 49.
+5 V
VSET
RSET
ISET_RESISTOR
AVDD
Reference
Int. / Ext.
GREF
SREF
PREFB
Buffer and
Control Circuit
VSET
PTS
AGND
PRECISION_I_OUTPUT
Load
AMC7823
IO
Figure 49. Diagram of Current Source
In addition to the external setting resistor RSET, four logic bits—PTS and PREFB in the Power-Down Register and
SREF and GREF in the AMC Status/Configuration Register—are used to configure the current source as well.
Table 7 describes how to configure the current source.
The bit PTS is the current source power-down bit. When PTS is cleared to '0', the current source is in
power-down mode, and the output current is zero. When PTS is set to '1' and PREFB is set to '1', the current
source is in normal operation.
Bit SREF is the reference source selection bit. When SREF is cleared, the internal reference is selected. When
SREF is set to '1', the internal reference is de-selected. Set SREF = 1 when an external reference is applied.
GREF is the internal reference gain bit. PREFB is the Reference Buffer Amplifier Power-Down bit. Both bits
provide information to the current source circuit, and affect the current source configuration.
If the internal reference is used, and no external reference is applied to pin 21, the output current is 0.5 V/RSET
(VSET = 0.5 V) or zero, depending on bits PREFB and GREF, as shown in Table 7.
For a precise calculation, measure the voltage across the set resistor (VSET) and divide it by the precise value of
RSET.
32
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
Table 7. Precision Current Source Configuration
(1)
(2)
SREF
PTS
PREFB
GREF
IO
0
0
Don't care
Don't care
0
0
1
0
1
0
0
1
Don't care
0
0.5V/RSET (1)
0
1
1
1
0.5V/RSET (1)
1
0
Don't care
Don't care
0
1
1
0
1 (2)
0
1
1
Don't care
0 (2)
Equation 1
1
1
1
1 (2)
Equation 1
VSET = 0.5 V.
Make GREF = 1 for 2.5-V external reference; make GREF = 0 for 1.25-V external reference.
When an external reference is used, select a reference value (VREF) close to either 1.25 V or 2.5 V, and write bit
GREF low ('0') for a 1.25-V reference, or write it high ('1') for a 2.5-V reference. These settings make a better
match to the applied external reference value. The output current can be calculated by Equation 1:
I OUTPUT V REF 0.4
V SET
R SET 1GREF R SET
(1)
The applied external reference voltage may deviate from the recommended values, but it is important to limit the
maximum voltage applied to the set resistor to approximately 0.5 V. Voltages greater than 0.5 V across the set
resistor reduce the specified compliance of the current source to the load.
DIGITAL I/O (See AMC Status/Configuration Register)
The AMC7823 has four special function pins: DAV, GALR, ELDAC, and CONVERT, It also has six general I/O
pins (GPIO-n). The GPIO-n pins are used as general digital I/O or analog input out-of-range indicators.
The pin DAV is an output pin that indicates the completion of ADC conversions. Bit DAVF of the AMC
Status/Configuration Register determines the status of the DAV pin. In direct-mode, after the selected group of
input channels has been converted and the ADC has been halted, bit DAVF is set to '1' and pin DAV is driven to
logic low (active). In auto-mode, each time the group of input channels has been sequentially converted, a 2-µs
pulse (low) appears on the DAV pin after the last channel of the group is converted. This conversion sequence is
repeated and the pulse is repeated.
The GALR pin is an output pin that indicates whether any of the first four analog inputs being converted are
out-of-range. Bits ALR-n of the ALR Register determine the status of GALR pin. GALR is low (or active) if any
one of the bits ALR-n is set to '1'. GALR is high (inactive) if and only if all bits are cleared to '0'. See Figure 50.
DAV Pin in Direct Mode
Bit DAVF of AMC
Status / Configuration
Register
DAV Pin
DAV Pin in Auto-Mode
[EA3:EA0] is
Converted
Bit
Bit
Bit
Bit
2-µs Pulse
Generator
ALR−0
ALR−1
ALR−2
ALR−3
DAV Pin
GALR Pin
Figure 50. DAV Pin and GALR Pin
The CONVERT pin is an input pin for the external ADC trigger signal. When bit ECNVT of the AMC
Status/Configuration Register is set to '1', the AMC7823 works in external trigger mode. The rising edge of
CONVERT starts the ADC conversion.
33
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
The ELDAC pin is an input pin for the external DAC synchronous load signal. The rising edge of ELDAC updates
all DAC-n simultaneously that have the corresponding bit SLDA-n set to '1'.
The AMC7823 has six GPIO pins, GPIO-n (n = 0, 1, 2, 3, 4, 5). Pins GPIO-4 and GPIO-5 are dedicated to
general bidirectional digital I/O signals. The remaining pins (n = 0, 1, 2, 3) are dual-purpose pins, and can be
programmed as either bidirectional GPIO or ALR (out-of-range alarm) indicators. Figure 51 shows the pin
structure of GPIO-4 and GPIO-5. See Figure 52 for the pin structure of GPIO-n (n = 0, 1, 2 and 3).
The bit IOMOD-n (n = 0, 1, 2, 3) in the GPIO register defines the function of these dual-purpose GPIO-n pins
(see Table 8). When the corresponding IOMOD-n bit is cleared to '0', GPIO-n pins are configured as out-of-range
indicators (denoted ALR-0, ALR-1, ALR-2, and ALR-3) for the first four analog inputs being converted. As an
out-of-range indicator, the ALR-n pin is an output whose status is determined by bits ALR-0, ALR-1, ALR-2, and
ALR-3 of the ALR Register. When ALR-n is set to '1', the ALR-n pin is low. When ALR-n is cleared to '0', the
ALR-n pin is in high impedance status. When IOMOD-n is set to '1', the GPIO-n pin works as a general,
bidirectional digital I/O pin.
Table 8. GPIO Function
IOMOD-n
PIN NAME
1
0
GPIO-0
GPIO
ALR-0
GPIO-1
GPIO
ALR-1
GPIO-2
GPIO
ALR-2
GPIO-3
GPIO
ALR-3
When the GPIO-n pin works as general, bidirectional digital I/O, it can receive an input or produce an output.
(See Figure 51 and Figure 52.) When acting as output, its status is determined by the corresponding bit IOST-n
(I/O Status) of the GPIO Register. The output is high impedance when bit IOST-n is set to '1' and is logic low
when bit IOST-n is cleared to '0'. An external pull-up resistor is required when using GPIO-n as output.
When GPIO-n acts as input, the digital value on the pin is acquired by reading the bit IOST-n.
After power-on reset or any forced hardware or software reset, all IOMOD-n and IOST-n bits are set to '1', and all
GPIO pins work as general I/O pins in high impedance status. See the GPIO Register for more detail.
GPIO-n
ENABLE
IOST-n
(when writing IOST-n)
IOST-n
(when reading IOST-n)
Figure 51. Pin Structure of GPIO-4 and GPIO-5
34
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
Bit ALR-n of ALR Register
Bit IOMOD-n
in GPIO Register
Bit IOST-n
in GPIO Register
GPIO-n
ENABLE
IOMOD-n = 0, ALR-n Pin
IOMOD-n = 1, Digital I/O Pin
Bit IOST-n
(when reading)
Figure 52. Pin Structure of GPIO-0, GPIO-1, GPIO-2, and GPIO-3
ANALOG INPUT OUT-OF-RANGE ALARM (See ADC Operation)
The AMC7823 provides out-of-range detection for the first four analog inputs of the group of inputs specified by
the starting and ending addresses [SA3:SA0] and [EA3:EA0], respectively. Figure 53 describes the analog
out-of-range logic. Alarm bits ALR-n in the ALR Register are set to '1' to flag an out-of-range condition. If the nth
analog input is out of the preset range, then bit ALR-n is set to '1'. The nth alarm bit does not necessarily
correspond to input channel address n, however. For example, if [SA3:SA0] and [EA3:EA0] of the ADC Control
Register are 0x04 and 0x07, respectively, then the channel address of the first analog input is [0x04] and the
corresponding alarm bit is ALR-0. The address of the fourth input channel is [0x07] and its corresponding alarm
bit is ALR-3. Only the first four analog inputs can be implemented with out-of-range detection. In this example,
the addresses of the first four inputs implemented with out-of-range detection are [0x04], [0x05], [0x06], and
[0x07], respectively. However, if [SA3:SA0] is equal to [0x00] and [EA3:EA0] is equal to [0x07], then the
addresses of the first four are [0x00], [0x01], [0x02] and [0x03].
Threshold-Hi-n
Register
(Upper Bound)
−
+
Bit ALR-n of
ALR Register
nth Analog
Input
−
Threshold-Low-n
Register
(Lower Bound)
ALR−0
ALR−1
ALR−2
ALR−3
+
ALR-n is always ‘0’ when
Threshold-Low-n is equal to 0
and Threshold-Hi-n is equal to
full-scale of input.
GALR Pin
NOTE: Threshold-Hi-n must not be smaller than Threshold-Low-n. Otherwise, ALR-n is always '1'.
Figure 53. Analog Out-of-Range Alarm Logic
35
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
The value in the Threshold-Hi-n Register defines the upper bound threshold of the nth analog input, while the
value in Threshold-Low-n defines the lower bound. These two bounds specify a window for the out-of-range
detection. The out-of-range condition occurs when the input is set outside the window defined by these
boundaries. To implement single upper-bound threshold detection, the host processor can set the upper bound
to the desired value and the lower bound to zero. For lower-bound detection, the host can set the lower bound to
the desired value and the upper bound to the full-scale input.
To deactivate the alarm function (ALR-n always '0'), set the threshold registers to their default values as specified
in Table 2.
Note: The value of Threshold-Hi-n must not be less than the value of Threshold-Low-n; otherwise, ALR-n is
always set to '1' and the alarm indicator is always active.
If any out-of-range alarm occurs, the Global Alarm pin (GALR, pin 1) goes logic low. This function provides an
interrupt to the host so that it may query the ALR Register (alarm register) to determine which channels are
out-of-range.
The general-purpose I/O pins, GPIO-0, GPIO-1, GPIO-2 and GPIO-3, are dual-purpose and can be configured
as individual out-of-range alarm indicators denoted as ALR-0, ALR-1, ALR-2 and ALR-3 as discussed previously.
Each ALR-n pin displays the logical complement of of each corresponding ALR-n bit. For example, when an
alarm condition occurs, bit ALR-n is set to '1' and pin ALR-n goes logic low. For each GPIO-n pin configured as
an alarm, its corresponding IOST-n bit in the GPIO Register displays the complement of bit ALR-n. For example,
when bit ALR-n is set to '1', bit IOST-n is cleared to '0'. (Note that pins GPIO-4 and GPIO-5 are not dual-purpose,
and are general digital I/O pins only.)
CLEARING ALARM INDICATORS
In summary, the maximum alarm condition would have pin GALR (pin 1) and one or more pins ALR-n at logic
low, one or more bits IOST-n cleared to '0', and one or more bits ALR-n set to '1'. All of these remain in alarm
status until the alarm-causing conditions are removed and a new conversion is completed. When the ADC is
operating in auto-mode, the alarm indicators are displayed after the first 2-µs pulse on pin DAV following
detection of one or more of the first four input channels out-of-range. The selected group of input channels is
converted repeatedly and the alarm indicators remain constant until the offending inputs are corrected or until the
threshold window levels are adjusted. When the alarm-causing conditions are removed, the alarm indicators are
cleared after the first 2-µs pulse on DAV following removal.
When the ADC is operating in direct-mode, the alarm indicators are displayed after the first data valid signal
(DAV, pin 2, at logic low) following an out-of-range condition. The alarm indicators remain constant until either
the inputs are corrected or the threshold windows adjusted, and another convert command is issued and
completed.
In either operating mode, the alarm indicators may be cleared if a new conversion command is issued identifying
a subset of input channels not containing the channel or channels out of range.
The alarm indicators may also be cleared by a general hardware or software reset, or a power-on reset.
36
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
REGISTERS
This section describes each of the registers shown in the memory map of Table 2. The registers are named
descriptively, according to their respective functions.
NOTE: After power-on or reset, all ADC channels, all DACs, and the precision current source are in a
powered-down state. The user must write the Power-Down Register properly in order to activate the desired
components. For details, see the Power-Down Register section.
AMC Status/Configuration Register (Read/Write; see Figure 50, DAV Pin and GALR Pin)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
X
RSTC
DAVF
0
X
X
X
X
SREF
GREF
ECNVT
X
X
X
X
X
X : Don't Care
RSTC
RESET Complete Bit. This bit is set to '1' on power-up or reset. This bit can be cleared by writing
'0' to this location. The host cannot set this bit to '1'. This bit allows the host to determine if the
part has been configured after power-up, or if a reset has occurred to the AMC7823 without
knowledge of the host.
DAVF
ADC Data Available Flag. For direct-mode only. Always cleared (set to '0') in auto-mode (see ADC
Control Register).
DAVF = 1: The ADC conversions are complete and new data are available.
DAVF = 0: The ADC conversion is in progress (data is not ready) or the ADC is in Auto-Mode.
In direct-mode, bit DAVF sets the pin DAV. DAV goes low when DAVF = 1, and goes high when
DAVF = 0. In auto-mode, DAVF is always cleared to '0'. However, a 2-µs pulse (active low)
appears on the DAV pin when the input with ending address [EA3:EA0] is converted. DAVF is
cleared to '0' in one of three ways: (1) reading the ADC Data Register; (2) starting a new ADC
conversion; or (3) writing '0' to this bit.
Bit 12
Read-only. Always '0'.
SREF
Select Reference bit.
SREF = 0 (default condition): The internal reference is selected as the chip reference. It is
connected to pin 21, EXT_REF_IN, by a 10-kΩ resistor.
SREF = 1: The internal reference is de-selected and disconnected from pin 21 (EXT_REF_IN).
Pin 21 floats unless an external reference is applied. Always set SREF bit to '1' when an external
reference is applied; otherwise, the external reference must sink or source current. The current
value is the voltage difference between the external and internal reference divided by a 10-kΩ
resistance.
SREF also provides information to the precision current source and is used to configure that
source (see the Precision Current Source section for details). After power-on or reset, SREF is
cleared to '0'.
GREF
Gain of the internal reference voltage (VREF). This bit selects one of two preset values for the
internal reference voltage, but has no effect on the external reference. GREF also provides
information to the precision current source and is used to configure that source (see the Precision
Current Source section for details).
GREF = 0: The internal reference voltage is +1.25 V.
GREF = 1: The internal reference voltage is +2.5 V.
37
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
When an external reference is used and SREF is set to '1', GREF has no impact on the reference.
However, if SREF is cleared to '0', a 10-kΩ resistor is connected between pin 21, EXT_REF_IN,
and one of the two internal reference values dictated by the value of GREF. In this case, the
external reference must be able to drive the 10-kΩ load. The full-scale range of the ADC input is
equal to 2 x VREF. To avoid ADC input saturation, GREF must be cleared to '0' when AVDD is less
than +5 V and the internal reference is used. After power-on or reset, GREF is cleared to '0'.
Table 9 specifies the ADC input range as a function of bits GREF and SREF.
Table 9. Reference and ADC Input Range Configuration
BIT GREF
BIT SREF
0
0
Internal reference, 1.25 V
1
0
Internal reference, 2.5 V, AVDD = 5 V only
Don't care
1
External reference VREF.
2 × VREF must not be greater than AVDD.
Set SREF = 1 when applying external reference.
ECNVT
REFERENCE
ADC INPUT RANGE
0 to 2.5 V
0 to 5 V
0 to 2 × VREF
Enable CONVERT (external conversion trigger). This bit specifies the ADC trigger mode. When
ECNVT = 1, CONVERT is enabled. The ADC is in external trigger mode. The low-to-high
transition of the external trigger signal CONVERT triggers the ADC conversions. A write command
to the ADC Control Register does not initiate conversion, but rather specifies the group of inputs
to convert. After triggered by CONVERT, the AMC7823 sequentially accesses each analog input
one time. The bits [SA3:SA0] of the ADC Control Register comprise the channel address of the
first analog input accessed; [EA3:EA0] is the last analog input accessed. When the conversion
finishes, the ADC is idle and waits for a new CONVERT or a new command. With an external
trigger, the ADC always works in direct-mode (see the ADC Control Register section).
When ECNVT = 0, CONVERT is disabled. The internal ADC trigger is used. A write command to
the ADC Control Register generates the internal trigger and initiates ADC conversion. With an
internal trigger, the ADC can work in either direct-mode or auto-mode (see the ADC Operation
and ADC Control Register sections). Table 10 summarizes the ADC conversion mode
configuration.
After power-on or reset, DAVF, SREF, GREF, and ECNVT are cleared to '0'; RSTC is set to '1'.
Table 10. ADC Conversion Mode Configuration
38
ECNVT of AMC STATUS/
CONFIGURATION REGISTER
CMODE of ADC
CONTROL REGISTER
ADC CONVERSION MODE
1
–
External Trigger, Direct-Mode
0
0
Internal Trigger, Direct-Mode
0
1
Internal Trigger, Auto-Mode
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
DAC Configuration Register (Read/Write)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
SLDA7
SLDA6
SLDA5
SLDA4
SLDA3
SLDA2
SLDA1
SLDA0
GDAC7
GDAC6
GDAC5
GDAC4
GDAC3
GDAC2
GDAC1
GDAC0
SLDA-n
DAC Synchronous Load Enable bit.
SLDA-n = 1: Synchronous Load enabled. When the synchronous load DAC signal occurs, DAC-n
Latch is loaded with the value of the corresponding DAC-n Data Register, and the output of
DAC-n is updated immediately. This load signal can be the rising edge of the external signal
ELDAC or the internal load signal ILDAC. Writing the data word 0xBB00 into the LOAD DAC
Register generates ILDAC. A write command to the DAC-n Data Register updates that register
only, and does not change the DAC-n output.
SLDA-n = 0: Asynchronous Load enabled. A write command to the DAC-n Data Register
immediately updates DAC-n Latch and the output of DAC-n. The synchronous load DAC signal
(ILDAC or ELDAC) does not affect DAC-n.
GDAC-n
DAC-n Output Buffer Amplifier Gain bit.
GDAC-n = 1: The gain of the DAC-n output buffer amplifier is equal to 2.
GDAC-n = 0: The gain of the DAC-n output buffer amplifier is equal to 1.
The combination of the bit GDAC-n and the reference voltage (internal or external) sets the full-scale range of
each DAC-n.
Table 11 describes the full-scale DAC output range as a function of bits SREF, GREF and GDAC-n.
Table 11. Full-Scale DAC Output Range
OUTPUT RANGE
SREF
GREF
GDAC-n
REFERENCE
AVDD = 3 V
AVDD = 5 V
0
0
0
Internal 1.25 V
0 V to 1.25 V
0 V to 1.25 V
0
0
1
Internal 1.25 V
0 V to 2.50 V
0 V to 2.50 V
0
1
0
Internal 2.5 V
0 V to 2.50 V
0 V to 2.50 V
0
1
1
Internal 2.5 V
Saturated at 3 V
0 V to 5.00 V
1
Don't
care
0
External VREF
0 V to External VREF,
External VREF ≤ AVDD
0 V to External VREF,
External VREF ≤ AVDD
1
Don't
care
1
External VREF
0 V to External VREF × 2
2 × External VREF ≤ AVDD
0 V to External VREF × 2
2 × External VREF ≤ AVDD
When an external reference is applied, the full-scale output range of DAC-n is equal to VREF for GDAC = 0, and
equal to 2 x VREF for GDAC-n = 1.
To avoid saturation, the full-scale output range of DAC-n must not be greater than AVDD. After power-on or reset,
all bits are cleared to '0'.
Load DAC Register (Read/Write)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
1
0
1
1
1
0
1
1
0
0
0
0
0
0
0
0
The data word 0xBB00 (shown above) written into the LOAD DAC Register generates ILDAC, the internal load
DAC signal. ILDAC and the external ELDAC signal work in a similar manner. ILDAC shifts data from the DAC-n
Data register to the DAC-n Latch and updates the output for all DAC-n with the corresponding SLDA-n bit set to
'1'. Other codes written to this register do not generate ILDAC and have no impact on any DAC-n. The LOAD
DAC Register is cleared after ILDAC is generated. The register is also cleared after power-on or reset.
39
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ADC Control Register (Read/Write; see ADC Operation and AMC Status/Configuration Register)
This register specifies the ADC conversion mode and identifies the analog inputs to be converted. A write
command to this register initiates conversion when the internal ADC trigger is selected (bit ECNVT = 0 in the
AMC Status/Configuration Register). However, when the external trigger is selected (bit ECNVT = 1), a write
command to this register does not start the conversion, but it does identify the analog inputs to be converted.
Internal trigger mode may employ either direct- or auto-mode conversion.
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
CMODE
X
X
X
SA3
SA2
SA1
SA0
EA3
EA2
EA1
EA0
X
X
X
X
X : Don't Care
CMODE
ADC Conversion Mode bit. This bit selects between the two operating conversion modes (direct
or auto) when the Internal trigger is active. This bit is always cleared to '0' (direct-mode) when an
external trigger is active.
CMODE = 0: Direct-mode. The analog inputs from [SA3:SA0] to [EA3:EA0] are converted
sequentially (see Table 12) one time, [SA3:SA0] first and [EA3;EA0] last. When one set of
conversions is complete, the ADC is idle and waits for a new trigger. The external trigger is
restricted to this mode of operation only.
CMODE = 1: Auto-mode. The analog inputs from [SA3:SA0] to [EA3:EA0] are converted
sequentially (see Table 12) and repeatedly, [SA3:SA0] first and [EA3;EA0] last. When one set of
conversions is complete, the ADC multiplexer returns to the starting address [SA3:SA0] and
repeats the process. Repetitive conversions continue until auto-mode is halted by rewriting the
ADC Control Register to direct-mode, or until the external trigger is enabled. Auto-mode works
only for the internal trigger.
SA3–SA0
The channel address of the first analog input to be converted (see Table 12).
EA3–EA0
The channel address of the last analog input to be converted (see Table 12).
The number of channels selected for conversion may range from one to nine. Channels in the selected range
[SA3:SA0] to [EA3:EA0] are addressed sequentially according to the map shown in Table 12. If the ending
channel address [EA3:EA0] is less than or equal to the starting address [SA3:SA0], then only channel [SA3:SA0]
is converted. After power-on or reset, the ADC Control Register is cleared (0x0000).
Channel CH8 is used for chip temperature measurement via the on-chip temperature sensor. It is not for external
analog input (see the On-chip Temperature Sensor section for details).
Table 12. Analog Input Channel Address Map
40
SA3/EA3
SA2/EA2
SA1/EA1
SA0/EA0
ANALOG INPUT
0
0
0
0
CH0
0
0
0
1
CH1
0
0
1
0
CH2
0
0
1
1
CH3
0
1
0
0
CH4
0
1
0
1
CH5
0
1
1
0
CH6
0
1
1
1
CH7
1
0
0
0
CH8
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ADC Data-n Registers (n = 0, 1, 2, 3, 4, 5, 6, 7, 8) (Read-Only)
Nine ADC Data registers are available. The ADC Data-n Registers store the conversion results of the
corresponding analog channel-n. The ADC-8 Data Register is used for the on-chip temperature sensor. The
other registers are for external analog inputs. All ADC Data-n registers are formatted in the manner shown here.
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
ICH3
ICH2
ICH1
ICH0
ADC11
ADC10
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADC11–ADC0
Value of the conversion result. The data is updated when the conversion of the input
[EA3:EA0] finishes; see the ADC Operation section for details.
ICH3–ICH0
Analog Input Channel number
After power-on or reset, all bits are cleared to '0'.
All ADC Data-n Registers are read-only. Writing to the ADC Data-n registers does not cause any change.
Table 13 summarizes the ADC Data-n Registers.
Table 13. ADC Data-n Registers
ICH3
ICH2
ICH1
ICH0
ANALOG INPUT
0
0
0
0
CH0
0
0
0
1
CH1
0
0
1
0
CH2
0
0
1
1
CH3
0
1
0
0
CH4
0
1
0
1
CH5
0
1
1
0
CH6
0
1
1
1
CH7
1
0
0
0
CH8
41
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
DAC-n Data Registers (n = 0, 1, 2, 3, 4, 5, 6, 7) (see the DAC Operation section)
This register is the input Data Register for DAC-n that buffers the DAC-n Latch Register. The DAC-n output is
updated only when Latch is loaded. Under an asynchronous load (bit SLDA-n = 0 in the DAC Configuration
Register), the value of the DAC-n Data Register is transferred into the Latch immediately after Data Register is
written. If a synchronous load is specified (SLDA-n = 1), then the DAC-n Latch is loaded with the value of the
DAC-n Data Register only after a synchronous load signal occurs. This signal can be either the internal ILDAC or
the rising edge of an external ELDAC (see DAC Operation and DAC Configuration Register discussions).
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
X
OCH2
OCH1
OCH0
DAC11
DAC10
DAC9
DAC8
DAC7
DAC6
DAC5
DAC4
DAC3
DAC2
DAC1
DAC0
X : Don't Care
DAC11–DAC0
(WRITE/READ)
In a write operation, these data bits are written into the DAC Data-n Register. However, in
a read operation, the data bits are returned from the DAC-n Latch, not from the DAC-n
Data Register.
OCH2–OCH0
DAC Address. Read-only. Writing these bits does not cause any change.
The registers are cleared to '0' after power-on or reset. Table 14 summarizes the DAC-n Data Registers.
Table 14. DAC-n Data Registers
42
OCH2
OCH1
OCH0
ANALOG OUTPUT
0
0
0
DAC0
0
0
1
DAC1
0
1
0
DAC2
0
1
1
DAC3
1
0
0
DAC4
1
0
1
DAC5
1
1
0
DAC6
1
1
1
DAC7
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
ALR Register (see Figure 53)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
X
X
X
X
ALR-3
ALR-2
ALR-1
ALR-0
X
X
X
X
0
0
0
0
X : Don't Care
The first four analog inputs in the group defined by bits [SA3:SA0] and [EA3:EA0] in the ADC Control Register
are implemented with out-of-range detection.
[Bit 3:Bit 0]
Must be '0' to ensure correct operation of alarm detection.
ALR- n (READ-ONLY)
nth analog input out-of-range status flag. These bits are read-only. Writing ALR-n
bits has no effect.
ALR-n = 1 when the nth analog input is out-of-range.
ALR-n = 0 when the nth analog input is not out-of-range. ALR-n is always '0' when
following conditions hold: the value of Threshold-Low-n Register is equal to '0', and
the Threshold-Hi-n Register is equal to the full-scale value of the input.
NOTE: To avoid loss of alarm data during power-down of the ADC, change to direct conversion mode (see ADC
Control Register) before power-down and do not issue a convert command while the ADC is powered down.
After power-on or reset, all bits in ALR Register are cleared to '0'. Reading the register does not clear any bits.
GPIO Register (Read/Write; see the Digital I/O section)
The AMC7823 has six general-purpose I/O (GPIO) pins to communicate with external devices. Pins GPIO-4 and
GPIO-5 are dedicated to general bidirectional, digital I/O signals. The remaining pins (n = 0, 1, 2, 3) are
dual-purpose and can be programmed as either GPIO pins or ALR (out-of-range) indicators. This register defines
the status of all GPIO pins and the functions of pins GPIO-0, GPIO-1, GPIO-2 and GPIO-3. The register is
formatted as shown here.
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
1
1
1
1
IOMOD3
IOMOD2
IOMOD1
IOMOD0
1
1
IOST5
IOST4
IOST3
IOST2
IOST1
IOST0
IOMOD- n
Function mode definition bit for pins GPIO-0, GPIO-1, GPIO-2, and GPIO-3 (see Table 8
and Figure 52)
IOMOD- n = 0
Analog input out-of-range detection mode. In this mode, GPIO-n (n =0, 1, 2, 3) work as
analog input out-of-range indicators, denoted as output pins ALR-n. The status of each pin
ALR-n is set by bit ALR-n of the ALR Register. The ALR-n pin is low when the
corresponding ALR-n bit is '1', and is high-impedance when ALR-n is '0'.
IOMOD- n = 1
GPIO mode. In this mode, pin GPIO-n works as general digital I/O (bidirectional). When
the pin is output, the status is determined by the corresponding bit IOST-n; it is
high-impedance for IOST-n = 1, and logic low for IOST-n = 0. When the pin is input,
reading this bit acquires the digital logic value present at the pin. GPIO data are preserved
during all power-down conditions.
IOST- n
I/O STATUS bit of the GPIO-n pin. If the GPIO-n pin works as a general-purpose I/O, this
bit indicates the actual logic value present at the pin when reading the bit. It also sets the
state of the corresponding GPIO-n pin (high-impedance for IOST-n = 1, logic low for
IOST-n = 0) when writing to the bit. An external pull-up resistor is required when using pin
GPIO-n as an output.
If the GPIO-n pin works as an analog input out-of-range indicator, then bit IOST-n is a
complement of the corresponding bit ALR-n in the ALR Register. Writing the IOST-n bit
does not cause any change. Note that only GPIO-0, GPIO-1, GPIO-2, and GPIO-3 can be
configured as out-of-range indicators.
43
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
To avoid loss of alarm information in bits IOST-n during power-down of the ADC, change to direct conversion
mode (see ADC Control Register) before power-down and do not issue a convert command while the ADC is
powered down.
NOTE: When GPIO-n works as a general-purpose I/O pin, bit IOST-n does not change during the power-down
procedure.
After power-on or reset, all bits in the GPIO Register are set to '1'. All GPIO pins are configured as general I/O
pins and are in high-impedance state.
THRESHOLD REGISTERS
Threshold-Hi-n and Threshold-Low-n (n = 0, 1, 2, 3) define the upper bound and lower bound of the nth analog
input range. (See Table 2.) This window determines whether the nth input is out-of-range. When the input is
outside the window, the corresponding bit ALR-n in the ALR Register is set to '1'.
For normal operation, the value of Threshold-Hi-n must be greater than the value of Threshold-Low-n; otherwise,
ALR-n is always set to '1' and an alarm is indicated.
Threshold-Hi-n Registers (n = 0, 1, 2, 3) (Read/Write)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
0
0
0
0
THRH11
THRH10
THRH9
THRH8
THRH7
THRH6
THRH5
THRH4
THRH3
THRH2
THRH1
THRH0
Bits [15:12]
(READ-ONLY)
'0' when read back. Writing these bits causes no change.
THRH11–THRH0
Data bits of the upper bound threshold of the nth analog input. All bits are set to '1'
after power-on or reset.
Threshold-Low-n Registers (n = 0, 1, 2, 3) (Read/Write)
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
0
0
0
0
THRL11
THRL10
THRL9
THRL8
THRL7
THRL6
THRL5
THRL4
THRL3
THRL2
THRL1
THRL0
Bits [15:12]
(READ-ONLY)
Always '0' when read back. Writing these bits causes no change.
THRL11–THRL0
Data bits of the lower bound threshold of the nth analog input. This register is
cleared to '0' after power-on or reset.
RESET Register (Read/Write)
The AMC7823 has a special RESET Register that performs the software equivalent function of the device
RESET pin. To invoke a system reset, write the data word 0xBB3X to this register. Only the upper 12 bits are
significant; the lowest four bits are Don’t Care.
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
1
0
1
1
1
0
1
1
0
0
1
1
X
X
X
X
X : Don't Care
Any other value written to this register has no effect. After power-on or reset, this register is cleared to all zeros.
Therefore, the value 0x0000 is always read back from this register.
44
AMC7823
www.ti.com
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
Power-Down Register (Read/Write)
NOTE: After power-on or reset, all bits in the Power-Down Register are cleared to '0', and all the components
controlled by this register are in the powered-down or Off state. To avoid loss of alarm data during power-down
of the ADC, change to direct conversion mode (see ADC Control Register) before power-down and do not issue
a convert command while the ADC is powered down.
The Power-Down Register allows the host to manage power dissipation of the AMC7823. When not required, the
ADC, the precision current source, the reference buffer amplifier or any of the DACs may be put in power-down
mode to reduce current drain from the supply. Bits in the Power-Down Register control this power-down function.
Bit 15
MSB
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LSB
PADC
PDAC7
PDAC6
PDAC5
PDAC4
PDAC3
PDAC2
PDAC1
PDAC0
PTS
PREFB
X
X
X
X
X
X : Don't Care
PADC
ADC power-down control bit.
PADC = 0: The ADC is in power-down mode and ADC conversion is halted.
PADC = 1: The ADC is in normal operating mode.
PDAC- n
(n = 0, 1, 2, 3, 4, 5, 6, 7)
DAC-n output buffer amplifier power-down control bit.
PDAC-n = 0: DAC-n output buffer amplifier is in power-down mode. The output pin
of DAC-n is internally switched from the buffer output to analog ground through an
internal 5-kΩ resistor. Each DAC output buffer may be independently powered
down. (See the DAC Operation section for details.)
PDAC-n = 1 and PREFB = 1: DAC-n is in normal operating mode.
PTS
Precision current source power-down control bit.
PTS = 0: Precision current source is in power-down mode and the current output is
zero.
PTS = 1: Precision current source is in normal operating mode (see the Precision
Current Source section for details).
PREFB
Reference buffer amplifier power-down control bit. This bit controls the power-down
condition of the amplifier that supplies a buffered reference voltage to all DAC-n
resistor strings and to the precision current source. This bit also provides
configuration information to the precision current source (see the Precision Current
Source Configuration table, Table 7).
PREFB = 0: Reference buffer amplifier is in power-down mode. All DACs are
inoperative. The precision current source may be used only if GREF = 0 (see the
Precision Current Source Configuration table, Table 7).
PREFB = 1: Reference buffer amplifier is powered on. This mode is required for any
DAC-n operation. The precision current source may be used with either value of
GREF.
45
PACKAGE OPTION ADDENDUM
www.ti.com
7-Oct-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
AMC7823IRTAR
ACTIVE
QFN
RTA
40
2000
TBD
Call TI
Call TI
AMC7823IRTAT
ACTIVE
QFN
RTA
40
250
TBD
Call TI
Call TI
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS) 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.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI 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 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. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DSP
dsp.ti.com
Broadband
www.ti.com/broadband
Interface
interface.ti.com
Digital Control
www.ti.com/digitalcontrol
Logic
logic.ti.com
Military
www.ti.com/military
Power Mgmt
power.ti.com
Optical Networking
www.ti.com/opticalnetwork
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
Telephony
www.ti.com/telephony
Video & Imaging
www.ti.com/video
Wireless
www.ti.com/wireless
Mailing Address:
Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright  2005, Texas Instruments Incorporated