AMC7823
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SLAS453F – APRIL 2005 – REVISED MARCH 2012
ANALOG MONITORING AND CONTROL CIRCUIT
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FEATURES
APPLICATIONS
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12-Bit ADC (200kSPS):
– Eight Analog Inputs
– Input Range 0 to 2 × VREF
Programmable VREF, 1.25V or 2.5V
Eight 12-Bit DACs (2μs 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, 3V or 5V Logic Compatible
Single 3V to 5V Supply
Power-Down Mode/Low Power
Small Package (QFN-40, 6 x 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-ofrange 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
1
2
3
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 other 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 © 2005–2012, Texas Instruments Incorporated
AMC7823
SLAS453F – APRIL 2005 – REVISED MARCH 2012
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DESCRIPTION (CONTINUED)
The AMC7823 has an internal programmable reference (+2.5V or +1.25V), and an SPI serial interface. An
external reference can be used as well. Typical power dissipation is 100mW. The analog input range is 0V to
+5V, and the analog output range is 0V to +2.5V or 0V to +5V. 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 (1)
Over operating free-air temperature range, unless otherwise noted.
AMC7823
UNIT
AVDD, DVDD, BVDD to GND
PARAMETER
–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
±20
mA
Input current, continuous
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
θJC
15
°C/W
θJA
60
°C/W
Power dissipation
Thermal impedance
(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.
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ELECTRICAL CHARACTERISTICS: +5V
At –40°C to +85°C, AVDD = 5V, DVDD = 5V, BVDD = 3V to 5V, using external 2.5V reference, unless otherwise noted.
AMC7823
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
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
No missing codes
Integral linearity
Differential linearity
Bits
–1.25
+1.25
LSB (1)
–1
+1.25
LSB
Offset error
±2
Offset error drift
±4
Offset error match
0.5
Gain error
Gain error match
0.3
Noise
70
Power-supply rejection
AVDD = 5V ±5%
Sample rate (2)
Total conversion time
Bits
12
Scan Channels 0 through 7
LSB
ppmFS/°C
1
LSB
±6
LSB
1
LSB
μVRMS
70
dB
200
kHz
45
μs
Total conversion time including temperature Scan Channels 0 through 8
56
μs
Channel-to-channel isolation
0.5
LSB
VIN = 5VPP at 10kHz
DIGITAL-TO-ANALOG CONVERTER (3)
Output voltage range
Programmable
Output current
Refer to Typical Characteristics
0
2 × VREF
±1
Resolution
Integral linearity (4)
Monotonicity
mA
12
Bits
±2
±8
LSB
±0.2
±1
LSB
±0.5
±5
mV
±1
±10
12
Differential linearity
Offset error
V
Output range = 0 to VREF
Output range = 0 to 2 × VREF
Offset error drift
Bits
±4
Gain error
Output range = 0 to 2 × VREF
Settling time
Step between code 0x400 to 0xC00,
to ±1LSB
Code change glitch
1LSB change, in worst case
Overshoot
Step between code 0x400 to 0xC00
Crosstalk
Step between code 0x400 to 0xC00
< 0.5
LSB
Signal-to-noise ratio
Sine wave (1kHz, 5VPP) generated by DAC,
sampling at 400kSPS, RL = 10kΩ,
CL = 100pF
74
dB
Output buffer gain = 2
60
nV/√Hz
Output buffer gain = 1
30
nV/√Hz
Output noise voltage density
(1)
(2)
(3)
(4)
±0.3
mV
ppmFS/°C
±1.0
%FS
2
μs
20
nV-s
200
mV
LSB means least significant bit.
Single-channel conversion only. Does not include control logic delay associated with ADC operation, such as from the trigger signal to
the start of conversion.
DAC is tested with load of 25kΩ in parallel with 100pF to ground.
Measured from code 0x008 to 0xFFF.
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ELECTRICAL CHARACTERISTICS: +5V (continued)
At –40°C to +85°C, AVDD = 5V, DVDD = 5V, BVDD = 3V to 5V, using external 2.5V reference, unless otherwise noted.
AMC7823
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
10
mA
100.0
100.5
μA
PRECISION CURRENT SOURCE
Output current range
0.01
Output current accuracy
Iout = 100μA
99.5
Output current drift
Iout = 100μA
40
ppm/°C
Output impedance
Iout = 100μA
100
MΩ
Compliance voltage of pin
PRECISION_I_OUTPUT
Iout = 10mA
4.25
V
60
dB
3
Power-supply rejection ratio
VOLTAGE REFERENCE (VREF)
Internal reference voltage (5)
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
–40
°C
VREF = 2.5V
+3.2
°C
VREF = 1.25V
+1.6
°C
±4
°C
±2.0
°C
VREF = 2.5V
Accuracy
+85
VREF = 1.25V
LEVEL OF PIN GALR AND DAV
IOH = 0.7mA
2.4
BVDD
V
IOL = 180μA
0
0.4
V
DIGITAL INPUT/OUTPUT, EXCEPT PIN GALR AND DAV
VIH
BVDD = 5V, IIH = 5μA
3.5
BVDD + 0.3
V
VIL
BVDD = 5V, IIL = –5μA
0
0.8
V
VOH
Logic level
BVDD = 5V, IOH = –3mA
4
BVDD
V
VOL
BVDD = 5V, IOL = 3mA
0
0.4
V
VIH
BVDD = 3V, IIH = 5μA
2.1
BVDD + 0.3
V
VIL
VOH
Logic level
VOL
BVDD = 3V, IIL = –5μA
BVDD = 3V, IOH = –3mA
BVDD = 3V, IOL = 3mA
Input capacitance
(5)
4
0
0.6
V
2.4
BVDD
V
0
0.4
V
5
pF
Bit GREF in AMC Status/Configuration Register determines the internal reference voltage. The internal VREF = 2.5V when GREF = 1,
and the internal VREF = 1.25V when GREF = 0 (see AMC Status/Configuration Register for details).
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ELECTRICAL CHARACTERISTICS: +5V (continued)
At –40°C to +85°C, AVDD = 5V, DVDD = 5V, BVDD = 3V to 5V, using external 2.5V reference, unless otherwise noted.
AMC7823
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
2.7
5
UNIT
POWER-SUPPLY REQUIREMENTS
Powersupply
voltage
AVDD
DVDD
(6)
BVDD
(7)
Quiescent current of AVDD
5.5
V
2.7
5.5
V
2.7
5.5
V
In normal operation,
precision current source = 0, no DAC load
15
All power-down
20
mA
1
Quiescent current of DVDD
0.3
Quiescent current of BVDD
0.1
mA
mA
Power dissipation
100
mW
TEMPERATURE RANGE
Specified performance
–40
+85
°C
Storage
–65
+150
°C
(6)
(7)
DVDD must equal AVDD.
BVDD must not be greater than AVDD or DVDD.
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ELECTRICAL CHARACTERISTICS: +3V
At –40°C to +85°C, AVDD, DVDD, BVDD = 3V, using external 1.25V reference, unless otherwise noted.
AMC7823
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
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
No missing codes
12
Integral linearity
Differential linearity
Bits
–1.25
+1.25
LSB (1)
–1
+1.25
LSB
Offset error
±3
Offset error drift
±4
Offset error match
0.5
Gain error
Gain error match
0.3
Noise
70
Power-supply rejection
AVDD = 3V ±5%
Sample rate (2)
Total conversion time
Bits
Scan Channels 0 through 7
LSB
ppmFS/°C
1
LSB
±12
LSB
1.5
LSB
μVRMS
70
dB
200
kHz
47
μs
Total conversion time including temperature Scan Channels 0 through 8
58
μs
Channel-to-channel isolation
0.5
LSB
VIN = 2.5VPP at 10kHz
DIGITAL-TO-ANALOG CONVERTER (3)
Output voltage range
Programmable
Output current
Refer to Typical Characteristics
0
2 × VREF
±1
Resolution
Integral linearity (4)
Monotonicity
Offset error
mA
12
Bits
±2
±8
LSB
±0.2
±1
LSB
±0.5
±5
mV
±1
±10
12
Differential linearity
Output range = 0 to VREF
Output range = 0 to 2 x VREF
Offset error drift
V
Bits
±4
Gain error
Output range = 0 to 2 x VREF
Settling time
Step between code 0x400 to 0xC00,
to ±1LSB
Code change glitch
1LSB change, in worst case
Overshoot
Step between code 0x400 to 0xC00
Crosstalk
Step between code 0x400 to 0xC00
[EA] ?
No
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
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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 (750μA) and the forward voltage VBE1 is
measured. Next, the diode is driven by current I2 (10μA) and VBE2 is measured. The difference of these two
voltages, ΔVBE, 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 (750μA). During the second conversion, SW2 is turned on, SW1 is off, and the diode is
driven by I2 (10μA).
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:
ΔVBE (mV) = decimal code (convert from ADC-8 Data Register binary code) × 1.22mV for VREF = 2.5V
or
ΔVBE (mV) = decimal code (convert from ADC-8 Data Register binary code) × 0.61mV for VREF = 1.25V.
Temp (K) = 2.6 × ΔVBE (mV)
or
Temp (°C) = 2.6 × ΔVBE (mV) – 273K.
The resolution of this calculation is 3.2°C/LSB when the reference voltage is 2.5V and 1.6°C/LSB for a reference
voltage of 1.25V. The temperature sensor is powered by the reference. When the internal reference is used, a
filter capacitor (for example, 10μF) from pin 21 (EXT_REF_IN) to AGND is recommended to improve
temperature reading; refer to the Reference section for more information.
28
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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 5kΩ
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 are 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 are 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.
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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
The 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
30
SREF
GREF
GDAC-n
REFERENCE
AVDD = 3V
AVDD = 5V
0
0
0
Internal 1.25V
0V to 1.25V
0V to 1.25V
0
0
1
Internal 1.25V
0V to 2.5V
0V to 2.5V
0
1
0
Internal 2.5V
0V to 2.5V
0V to 2.5V
0
1
1
Internal 2.5V
Saturated at 3V
0V to 5V
1
Don't
care
0
External VREF
0V to External VREF,
External VREF ≤ AVDD
0V to External VREF,
External VREF ≤ AVDD
1
Don't
care
1
External VREF
0V to External VREF × 2
2 × External VREF ≤ AVDD
0V to External VREF × 2
2 × External VREF ≤ AVDD
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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 0V, gain of unity, and a full-scale output range preset to either 1.25V 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 0V. Thus, when the input code is 000h, the
output is typically 15mV to 20mV. 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
20mV. Near-zero-volt output for a particular DAC-n may be achieved by clearing bit PDAC-n to '0' in the PowerDown 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 5kΩ 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 GPIOs) 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 powerdown 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.
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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
10kΩ 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 [ (10kΩ) ×
(CFILTER) ]. The resistor also allows an external reference applied to pin 21 to override the internal reference,
provided it can drive the 10kΩ load. The filter capacitor can be 10μF when the internal reference is selected.
When using an external reference, it is recommended to use a buffered reference (such as the REF5025).
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 10kΩ 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 +1.25V. When GREF is set to '1', the internal reference voltage is +2.5V.
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 10kΩ. For
example, if SREF and GREF are both cleared to '0' and a 2.5V external reference is applied, the AMC7823 must
unnecessarily sink 125μA.
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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 powerdown 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 0.5V/RSET
(VSET = 0.5V) 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.
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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
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
1
(2)
0
0
1
1
0
1
1
Don't care
0 (2)
Equation 1
0
1
1
1
1 (2)
Equation 1
VSET = 0.5V.
Make GREF = 1 for 2.5V external reference; make GREF = 0 for 1.25V external reference.
When an external reference is used, select a reference value (VREF) close to either 1.25V or 2.5V, and write bit
GREF low ('0') for a 1.25V reference, or write it high ('1') for a 2.5V reference. These settings make a better
match to the applied external reference value. The output current can be calculated by Equation 1:
(VREF 0.4)
V
I OUTPUT + SET +
RSET
(1)GREF) RSET
(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 0.5V. Voltages greater than 0.5V across the set
resistor reduce the specified compliance of the current source to the load.
DIGITAL I/O (See the 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 2μs
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 outof-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
2ms Pulse
Generator
Bit ALR-0
Bit ALR-1
Bit ALR-2
Bit 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.
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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 outof-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
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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-ofrange 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)
−
+
nth Analog
Input
Threshold-Low-n
Register
(Lower Bound)
ALR-0
ALR-1
ALR-2
ALR-3
Bit ALR-n of
ALR Register
−
+
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
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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 outof-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 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 automode, the alarm indicators are displayed after the first 2μs 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 2μs
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.
POWER-ON RESET AND POWER-SUPPLY SEQUENCE
After power-on or reset, all registers are reset to the default values (see Table 2). In order for the device to work
properly, BVDD must not be applied before DVDD and AVDD are applied, and DVDD must not be applied before
AVDD is applied. All three supplies must power up before the external reference voltage (if any) is applied.
Additionally, because the DAC input shift register is not reset during a power-on reset (or during a hardware
reset or software reset), the SS pin must not be unintentionally asserted during power-up of the device. It is
recommended that the SS pin be connected to BVDD through a pull-up resistor to avoid improper power-up.
Likewise, the state of the ELDAC pin must be maintained at ground potential during power-up. To ensure that the
ESD protection circuitry of this device is not activated, all other digital pins must remain at ground potential until
BVDD is applied.
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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 powereddown 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
X
Bit 14
RSTC
Bit 13
DAVF
Bit 12
0
Bit 11
X
Bit 10
X
Bit 9
X
Bit 8
X
Bit 7
SREF
Bit 6
GREF
Bit 5
ECNVT
Bit 4
X
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
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 2μs 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 10kΩ 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 10kΩ
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 +1.25V.
GREF = 1: The internal reference voltage is +2.5V.
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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 10kΩ 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 10kΩ 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 +5V 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, 1.25V
1
0
Internal reference, 2.5V, AVDD = 5V 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 2.5V
0 to 5V
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
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
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DAC Configuration Register (Read/Write)
Bit 15
MSB
Bit 14 Bit 13 Bit 12 Bit 11 Bit 10
Bit 9
Bit 8
Bit 7
SLDA7 SLDA6 SLDA5 SLDA4 SLDA3 SLDA2 SLDA1 SLDA0 GDAC
7
SLDA-n
Bit 6
GDAC
6
Bit 5
GDAC
5
Bit 4
GDAC
4
Bit 3
GDAC
3
Bit 2
GDAC
2
Bit 1
GDAC
1
Bit 0
LSB
GDAC
0
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 DACn 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 = 3V
AVDD = 5V
0
0
0
Internal 1.25V
0V to 1.25V
0V to 1.25V
0
0
1
Internal 1.25V
0V to 2.50V
0V to 2.50V
0
1
0
Internal 2.5V
0V to 2.50V
0V to 2.50V
0
1
1
Internal 2.5V
Saturated at 3V
0V to 5.00V
1
Don't
care
0
External VREF
0V to External VREF,
External VREF ≤ AVDD
0V to External VREF,
External VREF ≤ AVDD
1
Don't
care
1
External VREF
0V to External VREF × 2
2 × External VREF ≤ AVDD
0V 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
1
Bit 14
0
Bit 13
1
Bit 12
1
Bit 11
1
Bit 10
0
Bit 9
1
Bit 8
1
Bit 7
0
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
LSB
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.
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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
CMOD
E
Bit 14
X
Bit 13
X
Bit 12
X
Bit 11
SA3
Bit 10
SA2
Bit 9
SA1
Bit 8
SA0
Bit 7
EA3
Bit 6
EA2
Bit 5
EA1
Bit 4
EA0
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
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 eight. Channels in the selected range
[SA3:SA0] to [EA3:EA0] are addressed sequentially according to the map shown in Table 12. The starting
address [SA3:SA0] must not be greater than the ending address [EA:3:EA0]. When the internal trigger is
selected, the staring address must be '0000' (that is, CH-0); otherwise, the ADC conversion may not be correct.
Table 13 shows the allowed range of analog input channels for each ADC conversion mode. 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
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
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Table 13. Analog Input Channel Range
STARTING CHANNEL
[SA3:SA0]
ENDING CHANNEL
[EA3:EA0]
External trigger,
direct mode
Any one of CH0 to CH8
Any one from CH0 to
CH8, but not less than
[SA3:SA0]
0
Internal trigger,
direct mode
CH0 only. SA3:SA0 = '0000'
Any one
1
Internal trigger,
auto mode
CH0 only. SA3:SA0 = '0000'
Any one
ECNVT
CMODE
ADC MODE
1
0
0
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
ICH3
Bit 14
ICH2
Bit 13
ICH1
Bit 12
ICH0
Bit 11
ADC1
1
Bit 10
ADC1
0
Bit 9
ADC9
Bit 8
ADC8
Bit 7
ADC7
Bit 6
ADC6
Bit 5
ADC5
Bit 4
ADC4
Bit 3
ADC3
Bit 2
ADC2
Bit 1
ADC1
Bit 0
LSB
ADC0
ADC11–ADC0
Value of the conversion result. The data are 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 14 summarizes the ADC Data-n Registers.
Table 14. ADC Data-n Registers
42
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
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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
X
Bit 14
OCH2
Bit 13
OCH1
Bit 12
OCH0
Bit 11
DAC1
1
Bit 10
DAC1
0
Bit 9
DAC9
Bit 8
DAC8
Bit 7
DAC7
Bit 6
DAC6
Bit 5
DAC5
Bit 4
DAC4
Bit 3
DAC3
Bit 2
DAC2
Bit 1
DAC1
Bit 0
LSB
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 15 summarizes the DAC-n Data Registers.
Table 15. DAC-n Data Registers
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
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ALR Register (see Figure 53)
Bit 15
MSB
X
Bit 14
X
Bit 13
X
Bit 12
X
Bit 11
ALR-3
Bit 10
ALR-2
Bit 9
ALR-1
Bit 8
ALR-0
Bit 7
X
Bit 6
X
Bit 5
X
Bit 4
X
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
LSB
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 dualpurpose 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
1
Bit 14
1
Bit 13
1
Bit 12
1
Bit 11
IOMO
D3
Bit 10
IOMO
D2
Bit 9
IOMO
D1
Bit 8
IOMO
D0
Bit 7
1
Bit 6
1
Bit 5
IOST5
Bit 4
IOST4
Bit 3
IOST3
Bit 2
IOST2
Bit 1
IOST1
Bit 0
LSB
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 highimpedance 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.
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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
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 11
THRH
11
Bit 10
THRH
10
Bit 9
THRH
9
Bit 8
THRH
8
Bit 7
THRH
7
Bit 6
THRH
6
Bit 5
THRH
5
Bit 4
THRH
4
Bit 3
THRH
3
Bit 2
THRH
2
Bit 1
THRH
1
Bit 0
LSB
THRH
0
Bits [15:12] (READONLY)
'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
0
Bit 14
0
Bit 13
0
Bit 12
0
Bit 0
Bit 11 Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
THRL1 THRL1 THRL9 THRL8 THRL7 THRL6 THRL5 THRL4 THRL3 THRL2 THRL1 THRL0
1
0
Bits [15:12] (READONLY)
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
1
Bit 14
0
Bit 13
1
Bit 12
1
Bit 11
1
Bit 10
0
Bit 9
1
Bit 8
1
Bit 7
0
Bit 6
0
Bit 5
1
Bit 4
1
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
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.
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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 the ADC conversion to direct 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 must be set properly
before operating the ADC, DAC, precision current source, and reference of this device. It is recommended that
the Power-Down Register be programmed after all other registers have been initialized.
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
PAD
C
Bit 14
PDAC7
Bit 13
PDAC
6
Bit 12
PDAC
5
Bit 11
PDAC4
Bit 10
PDAC
3
Bit 9
PDAC2
Bit 8
PDAC1
Bit 7
PDAC0
Bit 6
PTS
Bit 5
PREFB
Bit 4
X
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
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 5kΩ 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.
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REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (January 2010) to Revision F
Page
•
Changed Level of Pin GALR and DAV, IOH = 0.7mA parameter minimum and maximum specifications in +5V
Electrical Characteristics table .............................................................................................................................................. 4
•
Corrected typo in Digital Input/output, Except Pin GALR and DAV, VOL Logic level (BVDD = 5V) parameter test
condition in +5V Electrical Characteristics table ................................................................................................................... 4
•
Changed Digital Input/output, Except Pin GALR and DAV, VOL Logic level (BVDD = 3V) parameter symbol in +5V
Electrical Characteristics table .............................................................................................................................................. 4
Changes from Revision D (August 2008) to Revision E
•
Page
Deleted lead temperature (soldering) rows from Absolute Maximum Ratings table ............................................................ 2
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PACKAGE OPTION ADDENDUM
www.ti.com
14-Oct-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
AMC7823IRTAR
ACTIVE
WQFN
RTA
40
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
AMC7823
Samples
AMC7823IRTAT
ACTIVE
WQFN
RTA
40
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
AMC7823
Samples
AMC7823IRTATG4
ACTIVE
WQFN
RTA
40
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
AMC7823
Samples
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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