Microchip MCP4822-E/SN 12-bit dacs with internal vref and spiâ ¢ interface Datasheet

MCP4821/MCP4822
12-Bit DACs with Internal VREF and SPI™ Interface
Features
Description
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The Microchip Technology Inc. MCP482X devices are
2.7V–5.5V, low-power, low DNL, 12-bit Digital-to-Analog
Converters (DACs) with internal band gap voltage
reference, optional 2x-buffered output and Serial
Peripheral Interface (SPI™).
The MCP482X family of DACs provide high accuracy
and low noise performance for industrial applications
where calibration or compensation of signals (such as
temperature, pressure and humidity) are required.
The MCP482X devices are available in the extended
temperature range and PDIP, SOIC and MSOP
packages.
The MCP482X devices utilize a resistive string
architecture, with its inherent advantages of low DNL
error, low ratio metric temperature coefficient and fast
settling time. These devices are specified over the
extended temperature range. The MCP482X family
includes double-buffered registers, allowing simultaneous updates using the LDAC pin. These devices also
incorporate a Power-On Reset (POR) circuit to ensure
reliable power-up.
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Set Point or Offset Trimming
Sensor Calibration
Precision Selectable Voltage Reference
Portable Instrumentation (Battery-Powered)
Calibration of Optical Communication Devices
Package Types
8-Pin PDIP, SOIC, MSOP
VDD 1
Block Diagram
CS
SDI
SCK
CS 2
LDAC
SCK 3
Power-on
Reset
Interface Logic
VDD
AVSS
Input
Register A
DACA
Register
Input
Register B
DACB
Register
SDI 4
CS 2
SCK 3
SDI 4
String
DACA
Gain
Logic
8 VOUTA
7 AVSS
6 SHDN
5 LDAC
8-Pin PDIP, SOIC, MSOP
VDD 1
2.048V
VREF
MCP4821
Applications
MCP4822
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•
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12-Bit Resolution
±0.2 LSb DNL (typ.)
±2 LSb INL (typ.)
Single or Dual Channel
Rail-to-Rail Output
SPI™ Interface with 20 MHz Clock Support
Simultaneous Latching of the Dual DACs
with LDAC pin
Fast Settling Time of 4.5 µs
Selectable Unity or 2x Gain Output
2.048V Internal Band Gap Voltage Reference
50 ppm/°C VREF Temperature Coefficient
2.7V to 5.5V Single-Supply Operation
Extended Temperature Range: -40°C to +125°C
8 VOUTA
7 AVSS
6 VOUTB
5 LDAC
String
DACB
Gain
Logic
Output
Op Amps
Output
Logic
VOUTA
SHDN
© 2005 Microchip Technology Inc.
VOUTB
DS21953A-page 1
MCP4821/MCP4822
1.0
ELECTRICAL
CHARACTERISTICS
† Notice: Stresses above those listed under “Maximum
Ratings” may cause permanent damage to the device. This is
a stress rating only and functional operation of the device at
those or any other conditions above those indicated in the
operational listings of this specification is not implied.
Exposure to maximum rating conditions for extended periods
may affect device reliability.
Absolute Maximum Ratings †
VDD ............................................................................................................. 6.5V
All inputs and outputs ...................AVSS – 0.3V to VDD + 0.3V
Current at Input Pins ....................................................±2 mA
Current at Supply Pins ...............................................±50 mA
Current at Output Pins ...............................................±25 mA
Storage temperature .....................................-65°C to +150°C
Ambient temp. with power applied ................-55°C to +125°C
ESD protection on all pins ........... ≥ 4 kV (HBM), ≥ 400V (MM)
Maximum Junction Temperature (TJ) . .........................+150°C
5V AC/DC CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x,
RL = 5 kΩ to GND, CL = 100 pF, TA = -40 to +85°C. Typical values at +25°C.
Parameters
Sym
Min
Typ
Max
Units
Input Voltage
VDD
2.7
—
5.5
Input Current - MCP4821
Input Current - MCP4822
IDD
—
—
330
415
400
750
µA
Conditions
Power Requirements
Hardware Shutdown Current
ISHDN
—
0.3
2
µA
Software Shutdown Current
ISHDN_SW
—
3.3
6
µA
Power-on-Reset Threshold
VPOR
—
2.0
—
V
Digital inputs grounded, Output
unloaded, code = 0x000
DC Accuracy
Resolution
n
12
—
—
Bits
INL Error
INL
-12
2
12
LSb
DNL (Note 1)
DNL
-0.75
±0.2
+0.75
LSb
Offset Error
VOS
-1
±0.02
1
% of FSR
VOS/°C
—
0.16
—
ppm/°C
-45°C to 25°C
—
-0.44
—
ppm/°C
+25°C to 85°C
gE
-2
-0.10
2
% of FSR
ΔG/°C
—
-3
—
ppm/°C
VREF
2.008
2.048
2.088
V
ΔVREF/°C
—
125
325
ppm/°C
-40°C to 0°C
—
0.25
0.65
LSb/°C
-40°C to 0°C
Offset Error Temperature
Coefficient
Gain Error
Gain Error Temperature
Coefficient
Device is monotonic
Code = 0x000h
Code 0xFFFh, not including offset
error
Internal Voltage Reference (VREF)
Nominal Reference Voltage
Temperature Coefficient
(Note 1)
Output Noise (VREF Noise)
Output Noise Density
1/f Corner Frequency
Note 1:
2:
VOUTA when G = 1x and
Code = 0xFFFh
—
45
160
ppm/°C
0°C to +85°C
—
0.09
0.32
LSb/°C
0°C to +85°C
ENREF
(0.1-10 Hz)
—
290
—
µVp-p
Code = 0xFFFh, G = 1
eNREF
(1 kHz)
—
1.2
—
µV/√Hz
Code = 0xFFFh, G = 1
eNREF
(10 kHz)
—
1.0
—
µV/√Hz
Code = 0xFFFh, G = 1
fCORNER
—
400
—
Hz
By design, not production tested.
Too small to quantify.
DS21953A-page 2
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
5V AC/DC CHARACTERISTICS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x,
RL = 5 kΩ to GND, CL = 100 pF, TA = -40 to +85°C. Typical values at +25°C.
Parameters
Sym
Min
Typ
Max
Units
Conditions
Output Swing
VOUT
—
0.010 to
VDD – 0.040
—
Phase Margin
PM
—
66
—
°
Slew Rate
SR
—
0.55
—
V/µs
ISC
—
15
24
mA
tSETTLING
—
4.5
—
µs
DAC-to-DAC Crosstalk
—
<10
—
nV-s
Note 2
Major Code Transition Glitch
—
45
—
nV-s
1 LSb change around major carry
(0111...1111 to 1000...0000)
Output Amplifier
Short Circuit Current
Settling Time
Accuracy is better than 1 LSb for
VOUT = 10 mV to (VDD – 40 mV)
Within 1/2 LSb of final value from
1/4 to 3/4 full-scale range
Dynamic Performance
Digital Feedthrough
—
<10
—
nV-s
Note 2
Analog Crosstalk
—
<10
—
nV-s
Note 2
Note 1:
2:
By design, not production tested.
Too small to quantify.
3V AC/DC CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = 3V, AVSS = 0V, VREF = 2.048V external, output buffer gain (G) = 1x,
RL = 5 kΩ to GND, CL = 100 pF, TA = -40 to +85°C. Typical values at 25°C
Parameters
Sym
Min
Typ
Max
Units
Input Voltage
VDD
2.7
—
5.5
Input Current - MCP4821
Input Current - MCP4822
IDD
—
—
300
415
400
750
µA
Conditions
Power Requirements
Hardware Shutdown Current
ISHDN
—
0.25
2
µA
Software Shutdown Current
ISHDN_SW
—
2
6
µA
Power-On Reset threshold
VPOR
—
2.0
—
V
Digital inputs grounded, Output
unloaded, code = 0x000
DC Accuracy
Resolution
n
12
—
—
Bits
INL Error
INL
-12
±3
12
LSb
DNL (Note 1)
DNL
-0.75
±0.3
0.75
LSb
VOS
-1
±0.02
1
% of FSR
VOS/°C
—
0.5
—
ppm/°C
-45°C to +25°C
—
-0.77
—
ppm/°C
+25°C to +85°C
gE
-2
-0.15
2
% of FSR
ΔG/°C
—
-3
—
ppm/°C
Offset Error
Offset Error Temperature
Coefficient
Gain Error
Gain Error Temperature
Coefficient
Note 1:
2:
Device is monotonic
Code 0x000h
Code 0xFFFh, not including offset error
By design, not production tested.
Too small to quantify.
© 2005 Microchip Technology Inc.
DS21953A-page 3
MCP4821/MCP4822
3V AC/DC CHARACTERISTICS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, VDD = 3V, AVSS = 0V, VREF = 2.048V external, output buffer gain (G) = 1x,
RL = 5 kΩ to GND, CL = 100 pF, TA = -40 to +85°C. Typical values at 25°C
Parameters
Sym
Min
Typ
Max
Units
Conditions
VREF
2.008
2.048
2.088
V
ΔVREF/°C
—
125
325
ppm/°C
-40°C to 0°C
—
0.25
0.65
LSb/°C
-40°C to 0°C
Internal Voltage Reference (VREF)
Nominal Reference Voltage
Temperature Coefficient
(Note 1)
VOUTA when G = 1x and
Code = 0xFFFh
—
45
160
ppm/°C
0°C to +85°C
—
0.09
0.32
LSb/°C
0°C to +85°C
ENREF
(0.1-10 Hz)
—
290
—
µVp-p
Code = 0xFFFh, G = 1
eNREF
(1 kHz)
—
1.2
—
µV/√Hz
Code = 0xFFFh, G = 1
eNREF
(10 kHz)
—
1.0
—
µV/√Hz
Code = 0xFFFh, G = 1
fCORNER
—
400
—
Hz
Output Swing
VOUT
—
0.010 to
VDD – 0.040
—
Phase Margin
PM
—
66
—
°
Slew Rate
SR
—
0.55
—
V/µs
ISC
—
14
24
mA
tSETTLING
—
4.5
—
µs
DAC-to-DAC Crosstalk
—
<10
—
nV-s
Note 2
Major Code Transition Glitch
—
45
—
nV-s
1 LSb change around major carry
(0111...1111 to
1000...0000)
Output Noise (VREF Noise)
Output Noise Density
1/f Corner Frequency
Output Amplifier
Short Circuit Current
Settling Time
Accuracy is better than 1 LSb for
VOUT = 10 mV to (VDD – 40 mV)
Within 1/2 LSb of final value from
1/4 to 3/4 full-scale range
Dynamic Performance
Digital Feedthrough
—
<10
—
nV-s
Note 2
Analog Crosstalk
—
<10
—
nV-s
Note 2
Note 1:
2:
By design, not production tested.
Too small to quantify.
5V EXTENDED TEMPERATURE SPECIFICATIONS
Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x,
RL = 5 kΩ to GND, CL = 100 pF. Typical values at +125°C by characterization or simulation.
Parameters
Sym
Min
Typ
Max
Input Voltage
VDD
Input Current - MCP4821
Input Current - MCP4822
IDD
2.7
—
5.5
—
—
350
440
—
Units
Conditions
Power Requirements
µA
Hardware Shutdown Current
ISHDN
—
1.5
—
µA
Software Shutdown Current
ISHDN_SW
—
5
—
µA
Power-On Reset threshold
VPOR
—
1.85
—
V
n
12
—
—
Bits
INL
—
±4
—
LSb
Digital inputs grounded, Output
unloaded, code = 0x000
DC Accuracy
Resolution
INL Error
Note 1:
2:
By design, not production tested.
Too small to quantify.
DS21953A-page 4
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
5V EXTENDED TEMPERATURE SPECIFICATIONS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x,
RL = 5 kΩ to GND, CL = 100 pF. Typical values at +125°C by characterization or simulation.
Parameters
Sym
Min
Typ
DNL (Note 1)
DNL
—
±0.25
—
LSb
Offset Error
VOS
—
±0.02
—
% of FSR
VOS/°C
—
-5
—
ppm/°C
gE
—
-0.10
—
% of FSR
ΔG/°C
—
-3
—
ppm/°C
VREF
—
2.048
—
V
ΔVREF/°C
—
125
—
ppm/°C
—
0.25
—
LSb/°C
-40°C to 0°C
—
45
—
ppm/°C
0°C to +85°C
Offset Error Temperature
Coefficient
Gain Error
Gain Error Temperature
Coefficient
Max
Units
Conditions
Device is monotonic
Code 0x000h
+25°C to +125°C
Code 0xFFFh, not including offset
error
Internal Voltage Reference (VREF)
Nominal Reference Voltage
Temperature Coefficient
(Note 1)
VOUTA when G = 1x and
Code = 0xFFFh
-40°C to 0°C
—
0.09
—
LSb/°C
ENREF
(0.1 - 10 Hz)
—
290
—
µVp-p
Code = 0xFFFh, G = 1
eNREF
(1 kHz)
—
1.2
—
µV/√Hz
Code = 0xFFFh, G = 1
eNREF
(10 kHz)
—
1.0
—
µV/√Hz
Code = 0xFFFh, G = 1
fCORNER
—
400
—
Hz
Output Swing
VOUT
—
0.010 to
VDD – 0.040
—
Phase Margin
PM
—
66
—
°
Slew Rate
SR
—
0.55
—
V/µs
Short Circuit Current
ISC
—
17
—
mA
tSETTLING
—
4.5
—
µs
DAC-to-DAC Crosstalk
—
<10
—
nV-s
Note 2
Major Code Transition Glitch
—
45
—
nV-s
1 LSb change around major carry
(0111...1111 to
1000...0000)
Output Noise (VREF Noise)
Output Noise Density
1/f Corner Frequency
0°C to +85°C
Output Amplifier
Settling Time
Accuracy is better than 1 LSb for
VOUT = 10 mV to (VDD – 40 mV)
Within 1/2 LSb of final value from
1/4 to 3/4 full-scale range
Dynamic Performance
Digital Feedthrough
—
<10
—
nV-s
Note 2
Analog Crosstalk
—
<10
—
nV-s
Note 2
Note 1:
2:
By design, not production tested.
Too small to quantify.
© 2005 Microchip Technology Inc.
DS21953A-page 5
MCP4821/MCP4822
AC CHARACTERISTICS (SPI™ TIMING SPECIFICATIONS)
Electrical Specifications: Unless otherwise indicated, VDD= 2.7V – 5.5V, TA= -40 to +125°C.
Typical values are at +25°C.
Parameters
Sym
Min
Typ
Max
Units
Schmitt Trigger High-Level
Input Voltage
(All digital input pins)
VIH
0.7 VDD
—
—
V
Schmitt Trigger Low-Level
Input Voltage
(All digital input pins)
VIL
—
—
0.2 VDD
V
VHYS
—
0.05 VDD
—
Input Leakage Current
ILEAKAGE
-1
—
1
μA
SHDN = LDAC = CS = SDI =
SCK + VREF = VDD or AVSS
Digital Pin Capacitance
(All inputs/outputs)
CIN,
COUT
—
10
—
pF
VDD = 5.0V, TA = +25°C,
fCLK = 1 MHz (Note 1)
Clock Frequency
FCLK
—
—
20
MHz
Clock High Time
tHI
15
—
—
ns
Note 1
Clock Low Time
tLO
15
—
—
ns
Note 1
tCSSR
40
—
—
ns
Applies only when CS falls with
CLK high. (Note 1)
Data Input Setup Time
tSU
15
—
—
ns
Note 1
Data Input Hold Time
tHD
10
—
—
ns
Note 1
SCK Rise to CS Rise Hold
Time
tCHS
15
—
—
ns
Note 1
CS High Time
tCSH
15
—
—
ns
Note 1
LDAC Pulse Width
tLD
100
—
—
ns
Note 1
LDAC Setup Time
tLS
40
—
—
ns
Note 1
tIDLE
40
—
—
ns
Note 1
Hysteresis of Schmitt Trigger
Inputs
CS Fall to First Rising CLK
Edge
SCK Idle Time before CS Fall
Note 1:
Conditions
TA = +25°C (Note 1)
By design and characterization, not production tested.
tCSH
CS
tIDLE
tCSSR
Mode 1,1
tHI
tLO
tCHS
SCK Mode 0,0
tSU
tHD
SI
MSb in
LSb in
LDAC
tLS
FIGURE 1-1:
DS21953A-page 6
tLD
SPI™ Input Timing.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
TEMPERATURE CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, VDD = +2.7V to +5.5V, AVSS = GND.
Parameters
Sym
Min
Typ
Max
Units
Specified Temperature Range
TA
-40
—
+125
°C
Operating Temperature Range
TA
-40
—
+125
°C
Storage Temperature Range
TA
-65
—
+150
°C
Thermal Resistance, 8L-PDIP
θJA
—
85
—
°C/W
Thermal Resistance, 8L-SOIC
θJA
—
163
—
°C/W
Thermal Resistance, 8L-MSOP
θJA
—
206
—
°C/W
Conditions
Temperature Ranges
Note 1
Thermal Package Resistances
Note 1:
The MCP482X family of DACs operate over this extended temperature range, but with reduced
performance. Operation in this range must not cause TJ to exceed the Maximum Junction Temperature of
+150°C.
© 2005 Microchip Technology Inc.
DS21953A-page 7
MCP4821/MCP4822
2.0
TYPICAL PERFORMANCE CURVES
Note:
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
0.3
0.1
INL (LSB)
DNL (LSB)
0.2
0
-0.1
-0.2
-0.3
0
1024
2048
3072
5
4
3
2
1
0
-1
-2
-3
-4
-5
Ambient Temperature
125C
4096
0
1024
Code (Decimal)
FIGURE 2-1:
DNL vs. Code.
FIGURE 2-4:
Temperature.
Absolute INL (LSB)
0.1
DNL (LSB)
2048
3072
Code (Decimal)
25
4096
INL vs. Code and Ambient
2.5
0.2
0
-0.1
2
1.5
1
0.5
0
-0.2
0
1024
2048
3072
Code (Decimal)
FIGURE 2-2:
Temperature.
125C
-40
4096
85C
-20
DNL vs. Code and Ambient
0
20
40
60
80
100
120
Ambient Temperature (ºC)
25C
FIGURE 2-5:
Temperature.
Absolute INL vs. Ambient
2
0.0766
0.0764
0
0.0762
INL (LSB)
Absolute DNL (LSB)
85
0.076
0.0758
0.0756
-2
-4
0.0754
0.0752
-6
0.075
-40
-20
0
20
40
60
80
0
100 120
1024
DS21953A-page 8
Absolute DNL vs. Ambient
3072
4096
Code (Decimal)
Ambient Temperature (ºC)
FIGURE 2-3:
Temperature.
2048
FIGURE 2-6:
Note:
INL vs. Code.
Single device graph for illustration of 64
code effect.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
2.050
2.049
2.048
2.047
2.046
2.045
2.044
2.043
2.042
2.041
2.040
100
1.E-04
Output Noise Voltage Density
(μV/—Hz)
Full Scale VOUT (V)
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
10
1.E-05
VDD: 4V
VDD: 3V
VDD: 2.7V
-40
-20
0
20
40
60
80
1
1.E-06
0.1
1.E-07
0.1
1E-1
100 120
1
1E+0
10
1E+1
FIGURE 2-7:
Full-Scale VOUTA w/G = 1
(VREF) vs. Ambient Temperature and VDD.
4.100
1k
1E+3
10k
1E+4
100k
1E+5
FIGURE 2-9:
Output Noise Voltage
Density (VREF Noise Density w/G = 1) vs.
Frequency.
1.E-02
10.0
4.096
4.092
Output Noise Voltage (mV)
Full Scale VOUT (V)
100
1E+2
Frequency (Hz)
Ambient Temperature (°C)
1.E-03
1.00
4.088
VDD: 5.5V
VDD: 5V
4.084
Eni (in VP-P)
0.10
1.E-04
4.080
4.076
-40
-20
0
20
40
60
80
100 120
Ambient Temperature (°C)
FIGURE 2-8:
Full-Scale VOUTA w/G = 2
(2VREF) vs.Ambient Temperature and VDD.
© 2005 Microchip Technology Inc.
Eni (in VRMS)
0.01
1.E-05
100
1E+2
Maximum Measurement Time = 10s
1k
1E+3
10k
100k
1E+4
1E+5
Bandwidth (Hz)
1M
1E+6
FIGURE 2-10:
Output Noise Voltage (VREF
Noise Voltage w/G = 1) vs. Bandwidth.
DS21953A-page 9
MCP4821/MCP4822
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
5.5V
5.0V
4.0V
3.0V
2.7V
VDD
320
IDD (μA)
300
280
260
240
600
5.5V
5.0V
4.0V
3.0V
2.7V
VDD
550
500
IDD (μA)
340
450
400
220
350
200
180
300
-40
-20
0
20
40
60
80
100
120
-40
-20
FIGURE 2-11:
MCP4821 IDD vs. Ambient
Temperature and VDD.
20
40
80
100
120
FIGURE 2-14:
MCP4822 IDD vs. Ambient
Temperature and VDD.
Occurrence
20
15
10
FIGURE 2-13:
(VDD = 5.0V).
DS21953A-page 10
MCP4821 IDD Histogram
440
430
425
420
435
435
430
425
420
350
>350
345
340
335
330
325
320
315
310
305
300
295
290
285
0
415
2
410
4
405
6
400
8
385
Occurrence
10
395
14
22
20
18
16
14
12
10
8
6
4
2
0
390
16
12
MCP4822 IDD Histogram
FIGURE 2-15:
(VDD = 2.7V).
18
IDD (μA)
415
IDD (μA)
MCP4821 IDD Histogram
FIGURE 2-12:
(VDD = 2.7V).
410
405
400
395
390
380
385
0
>320
320
315
310
305
300
295
290
285
280
275
270
5
IDD (μA)
Occurrence
60
25
20
18
16
14
12
10
8
6
4
2
0
265
Occurrence
0
Ambient Temperature (ºC)
Ambient Temperature (°C)
IDD (μA)
FIGURE 2-16:
(VDD = 5.0V).
MCP4822 IDD Histogram
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
0.7
ISHDN (μA)
0.5
0.4
0.3
0.2
-0.05
-0.1
VDD
-0.15
Gain Error (%)
5.5V
5.0V
4.0V
3.0V
2.7V
VDD
0.6
5.5V
5.0V
4.0V
3.0V
2.7V
-0.2
-0.25
-0.3
-0.35
-0.4
0.1
-0.45
-0.5
0
-40
-20
0
20
40
60
80
100
-40
120
-20
Ambient Temperature (ºC)
FIGURE 2-17:
Hardware Shutdown Current
vs. Ambient Temperature and VDD.
4
40
60
80
100
120
3
4.0V
2.5
3.0V
2.7V
2
VDD
1.5
VDD
4
5.0V
VIN Hi Threshold (V)
ISHDN_SW (μA)
20
FIGURE 2-20:
Gain Error vs. Ambient
Temperature and VDD.
5.5V
3.5
1
5.5V
3.5
5.0V
3
4.0V
2.5
2
3.0V
2.7V
1.5
1
-40
-20
0
20
40
60
80
100
120
-40
-20
Ambient Temperature (ºC)
0
20
40
60
80
100
120
Ambient Temperature (ºC)
FIGURE 2-18:
Software Shutdown Current
vs. Ambient Temperature and VDD.
FIGURE 2-21:
VIN High Threshold vs.
Ambient Temperature and VDD.
1.6
0.09
0.07
0.05
5.5V
0.03
VDD
0.01
5.0V
4.0V
3.0V
2.7V
-0.01
-0.03
-40
-20
0
20
40
60
80
100 120
Ambient Temperature (ºC)
FIGURE 2-19:
Offset Error vs. Ambient
Temperature and VDD.
© 2005 Microchip Technology Inc.
VIN Low Threshold (V)
0.11
Offset Error (%)
0
Ambient Temperature (ºC)
VDD
1.5
5.5V
1.4
5.0V
1.3
1.2
4.0V
1.1
1
3.0V
2.7V
0.9
0.8
-40
-20
0
20
40
60
80
100
120
Ambient Temperature (ºC)
FIGURE 2-22:
VIN Low Threshold vs.
Ambient Temperature and VDD.
DS21953A-page 11
MCP4821/MCP4822
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
16
2.5
5.5V
2
5.0V
1.75
1.5
4.0V
1.25
1
3.0V
2.7V
0.75
0.5
15
IOUT_HI_SHORTED (mA)
VIN_SPI Hysteresis (V)
5.5V
5.0V
4.0V
3.0V
2.7V
VDD
2.25
14
VDD
13
12
11
0.25
10
0
-40
-20
0
20
40
60
80
-40
100 120
-20
Ambient Temperature (ºC)
FIGURE 2-23:
Input Hysteresis vs. Ambient
Temperature and VDD.
40
60
80
100
120
6.0
4.0V
0.033
5.0
0.031
VREF = 4.096V
0.029
0.027
0.025
3.0V
0.023
2.7V
VDD
0.021
VOUT (V)
VOUT_HI Limit (VDD-Y)(V)
20
FIGURE 2-26:
IOUT High Short vs. Ambient
Temperature and VDD.
0.035
4.0
Output Shorted to VDD
3.0
2.0
1.0
0.019
0.017
Output Shorted to VSS
0.0
0.015
-40
-20
0
20
40
60
80
0
100 120
2
Ambient Temperature (ºC)
FIGURE 2-24:
VOUT High Limit vs. Ambient
Temperature and VDD.
0.0028
VOUT_LOW Limit (Y-AVSS)(V)
0
Ambient Temperature (ºC)
FIGURE 2-27:
4
6
8
10
IOUT (mA)
12
14
16
IOUT vs. VOUT. Gain = 2.
VDD
0.0026
0.0024
5.5V
0.0022
5.0V
0.0020
4.0V
3.0V
2.7V
0.0018
0.0016
0.0014
0.0012
0.0010
-40
-20
0
20
40
60
80
100 120
Ambient Temperature (ºC)
FIGURE 2-25:
VOUT Low Limit vs. Ambient
Temperature and VDD.
DS21953A-page 12
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF.
VOUT
VOUT
SCK
LDAC
LDAC
Time (1 µs/div)
FIGURE 2-28:
VOUT Rise Time 100%.
Time (1 µs/div)
FIGURE 2-31:
VOUT Rise Time 25% - 75%.
VOUT
VOUT
SCK
SCK
LDAC
LDAC
Time (1 µs/div)
VOUT Fall Time.
FIGURE 2-32:
Shutdown.
VOUT
SCK
LDAC
Time (1 µs/div)
FIGURE 2-30:
VOUT Rise Time Exit
Ripple Rejection (dB)
FIGURE 2-29:
Time (1 µs/div)
VOUT Rise Time 50%.
© 2005 Microchip Technology Inc.
Frequency (Hz)
FIGURE 2-33:
PSRR vs. Frequency.
DS21953A-page 13
MCP4821/MCP4822
3.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
PIN FUNCTION TABLE
MCP4821
Pin No.
MCP4822
Pin No.
Symbol
1
1
VDD
Positive Power Supply Input (2.7V to 5.5V)
2
2
CS
Chip Select Input
3
3
SCK
Serial Clock Input
4
4
SDI
Serial Data Input
5
5
LDAC
Synchronization input used to transfer DAC settings from serial
latches to output latches
6
—
SHDN
Hardware Shutdown Input
—
6
VOUTB
DACB Output
7
7
AVSS
Analog Ground
8
8
VOUTA
DACA Output
3.1
Function
Positive Power Supply Input (VDD)
VDD is the positive power supply input. The input power
supply is relative to AVSS and can range from 2.7V to
5.5V. A decoupling capacitor on VDD is recommended
to achieve maximum performance.
3.6
SHDN is the hardware shutdown input that requires an
active-low input signal to configure the DACs in their
low-power Standby mode.
3.7
3.2
Chip Select (CS)
CS is the chip select input, which requires an active-low
signal to enable serial clock and data functions.
Serial Clock Input (SCK)
DACx Outputs (VOUTA, VOUTB)
VOUTA and VOUTB are DAC outputs. The DAC output
amplifier drives these pins with a range of AVSS to VDD.
3.8
3.3
Hardware Shutdown Input (SHDN)
Analog Ground (AVSS)
AVSS is the analog ground pin.
SCK is the SPI compatible serial clock input.
3.4
Serial Data Input (SDI)
SDI is the SPI compatible serial data input.
3.5
Latch DAC Input (LDAC)
LDAC (the latch DAC synchronization input) transfers
the input latch registers to the DAC registers (output
latches) when low. Can also be tied low if transfer on
the rising edge of CS is desired.
DS21953A-page 14
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
4.0
GENERAL OVERVIEW
INL < 0
The MCP482X devices are voltage-output string DACs.
These devices include rail-to-rail output amplifiers,
internal voltage reference, shutdown and reset-management circuitry. Serial communication conforms to
the SPI protocol. The MCP482X devices operate from
2.7V to 5.5V supplies.
The coding of these devices is straight binary, with the
ideal output voltage given by Equation 4-1, where G is
the selected gain (1x or 2x), DN represents the digital
input value and n represents the number of bits of
resolution (n = 12).
EQUATION 4-1:
111
110
Actual
Transfer
Function
101
Digital
Input
Code
100
011
Ideal Transfer
Function
010
001
LSb SIZE
2.048V ⋅ G ⋅ D N
VOUT = ------------------------------------n
2
000
INL < 0
DAC Output
1 LSb is the ideal voltage difference between two
successive codes. Table 4-1 illustrates how to calculate
LSb.
TABLE 4-1:
LSb SIZES
Device
Gain
LSb Size
MCP482X
MCP482X
1x
2x
2.048V/4096
4.096V/4096
4.0.1
FIGURE 4-1:
4.0.2
Positive INL represents transition(s) later than ideal.
Negative INL represents transition(s) earlier than ideal.
DNL ACCURACY
DNL error is the measure of variations in code widths
from the ideal code width. A DNL error of zero would
imply that every code is exactly 1 LSb wide.
INL ACCURACY
INL error for these devices is the maximum deviation
between an actual code transition point and its corresponding ideal transition point once offset and gain
errors have been removed. These endpoints are from
0x000 to 0xFFF. Refer to Figure 4-1.
INL Accuracy.
111
110
Actual
Transfer
Function
101
Digital
Input
Code
100
Ideal Transfer
Function
011
010
001
Wide Code > 1 LSb
000
Narrow Code < 1 LSb
DAC Output
FIGURE 4-2:
4.0.3
DNL Accuracy.
OFFSET ERROR
Offset error is the deviation from zero voltage output
when the digital input code is zero.
4.0.4
GAIN ERROR
Gain error is the deviation from the ideal output,
VREF – 1 LSb, excluding the effects of offset error.
© 2005 Microchip Technology Inc.
DS21953A-page 15
MCP4821/MCP4822
4.1.1
Circuit Descriptions
OUTPUT AMPLIFIERS
5V
Supply Voltages
4.1
The DACs’ outputs are buffered with a low-power,
precision CMOS amplifier. This amplifier provides low
offset voltage and low noise. The output stage enables
the device to operate with output voltages close to the
power supply rails. Refer to Section 1.0 “Electrical
Characteristics” for range and load conditions.
In addition to resistive load-driving capability, the amplifier will also drive high capacitive loads without oscillation. The amplifiers’ strong outputs allow VOUT to be
used as a programmable voltage reference in a
system.
The rail-to-rail output amplifier has configurable gain,
allowing optimal full-scale outputs for differing voltage
reference inputs. The output amplifier gain has two
selections, a gain of 1 V/V (GA = 1) or a gain of 2 V/V
(GA = 0).
4.1.2
VOLTAGE REFERENCE
The MCP482X devices utilize internal 2.048V voltage
reference. The voltage reference has low temperature
coefficient and low noise characteristics. Refer to
Section 1.0 “Electrical Characteristics” for the
voltage reference specifications.
4.1.3
POWER-ON RESET CIRCUIT
The Power-On Reset (POR) circuit ensures that the
DACs power-up with SHDN = 0 (high-impedance). The
devices will continue to have a high-impedance output
until a valid Write command is performed to either of
the DAC registers and the LDAC pin meets the input
low threshold.
Transient Duration
10
Programmable Gain Block
The output range is ideally 0.000V to 4095/4096 *
2.048V when G = 1, and 0.000 to 4095/4096 * 4.096V
when G = 2. The default value for this bit is a gain of 2,
yielding an ideal full-scale output of 0.000V to 4.096V
due to the internal 2.048V VREF. Note that the near railto-rail CMOS output buffer’s ability to approach AVSS
and VDD establish practical range limitations. The
output swing specification in Section 1.0 “Electrical
Characteristics” defines the range for a given load
condition.
VDD - VPOR
Time
Transient Duration (µs)
4.1.1.1
VPOR
8
6
4
Transients above the curve
will cause a reset
2
0
FIGURE 4-3:
4.1.4
TA = +25°C
Transients below the curve
will NOT cause a reset
1
2
3
4
VDD – VPOR (V)
5
Typical Transient Response.
SHUTDOWN MODE
Shutdown mode can be entered by using either hardware or software commands. The hardware pin
(SHDN) is only available on the MCP4821. During
Shutdown mode, the supply current is isolated from
most of the internal circuitry. The serial interface
remains active, thus allowing a Write command to
bring the device out of Shutdown mode. When the output amplifiers are shut down, the feedback resistance
(typically 500 kΩ) produces a high-impedance path to
AVSS. The device will remain in Shutdown mode until
the SHDN pin is brought high and a write command
with SD = 1 is latched into the device. When a DAC is
changed from Shutdown to Active mode, the output
settling time takes < 10 µs, but greater than the
standard Active mode settling time (4.5 µs).
If the power supply voltage is less than the POR
threshold (VPOR = 2.0V, typical), the DACs will be held
in their reset state. They will remain in that state until
VDD > VPOR and a subsequent Write command is
received.
Figure 4-3 shows a typical power supply transient
pulse and the duration required to cause a reset to
occur, as well as the relationship between the duration
and trip voltage. A 0.1 µF decoupling capacitor,
mounted as close as possible to the VDD pin, provides
additional transient immunity.
DS21953A-page 16
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
5.0
SERIAL INTERFACE
5.1
Overview
5.2
The write command is initiated by driving the CS pin
low, followed by clocking the four configuration bits and
the 12 data bits into the SDI pin on the rising edge of
SCK. The CS pin is then raised, causing the data to be
latched into the selected DAC’s input registers. The
MCP482X devices utilize a double-buffered latch structure to allow both DACA’s and DACB’s outputs to be
synchronized with the LDAC pin, if desired. Upon the
LDAC pin achieving a low state, the values held in the
DAC’s input registers are transferred into the DACs’
output registers. The outputs will transition to the value
and held in the DACX register.
The MCP482X family is designed to interface directly
with the SPI port, available on many microcontrollers,
and supports Mode 0,0 and Mode 1,1. Commands and
data are sent to the device via the SDI pin, with data
being clocked-in on the rising edge of SCK. The
communications are unidirectional and, thus, data
cannot be read out of the MCP482X devices. The CS
pin must be held low for the duration of a write command. The write command consists of 16 bits and is
used to configure the DAC’s control and data latches.
Register 5-1 details the input registers used to
configure and load the DACA and DACB registers.
Refer to Figure 1-1 and the AC Electrical
Characteristics tables for detailed input and output timing specifications for both Mode 0,0 and Mode 1,1
operation.
REGISTER 5-1:
Write Command
All writes to the MCP482X devices are 16-bit words.
Any clocks past 16 will be ignored. The most significant four bits are configuration bits. The remaining 12
bits are data bits. No data can be transferred into the
device with CS high. This transfer will only occur if 16
clocks have been transferred into the device. If the
rising edge of CS occurs prior, shifting of data into the
input registers will be aborted.
WRITE COMMAND REGISTER
Upper Half:
W-x
W-x
W-x
W-0
W-x
W-x
W-x
W-x
A/B
—
GA
SHDN
D11
D10
D9
D8
bit 15
bit 8
Lower Half:
W-x
D7
bit 7
bit 15
W-x
D6
W-x
D5
W-x
D4
W-x
D3
W-x
D2
W-x
D1
W-x
D0
bit 0
A/B: DACA or DACB Select bit
Write to DACB
Write to DACA
1=
0=
bit 14
bit 13
—
Don’t Care
GA: Output Gain Select bit
1x (VOUT = VREF * D/4096)
2x (VOUT = 2 * VREF * D/4096)
1=
0=
bit 12
SHDN: Output Power-down Control bit
1 = Output Power-down Control bit
0 = Output buffer disabled, Output is high-impedance
bit 11-0
D11:D0: DAC Data bits
12-bit number “D” which sets the output value. Contains a value between 0 and 4095.
Legend
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
1 = bit is set
0 = bit is cleared
© 2005 Microchip Technology Inc.
x = bit is unknown
DS21953A-page 17
MCP4821/MCP4822
CS
0
1
2
3
4
5
6
7
8
9
10 11
12
13 14 15
SCK
(Mode 0,0)
config bits
SDI
(Mode 1,1)
A/B
12 data bits
— GA SHDN D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
LDAC
VOUT
FIGURE 5-1:
DS21953A-page 18
Write Command.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
6.0
TYPICAL APPLICATIONS
6.3
Output Noise Considerations
The MCP482X devices are general purpose DACs
intended to be used in applications where a precision,
low-power DAC with moderate bandwidth and internal
voltage reference is required.
The voltage noise density (in µV/√Hz) is illustrated in
Figure 2-9. This noise appears at VOUTX, and is primarily a result of the internal reference voltage. Its 1/f
corner (fCORNER) is approximately 400 Hz.
Applications generally suited for the MCP482X devices
include:
Figure 2-10 illustrates the voltage noise (in mVRMS or
mVP-P). A small bypass capacitor on VOUTX is an
effective method to produce a single-pole Low-Pass
Filter (LPF) that will reduce this noise. For instance, a
bypass capacitor sized to produce a 1 kHz LPF would
result in an ENREF of about 100 µVRMS. This would be
necessary when trying to achieve the low DNL
performance (at G = 1) that the MCP482X devices are
capable of. The tested range for stability is .001µF thru
4.7 µF.
Digital Interface
The MCP482X devices utilize a 3-wire synchronous
serial protocol to transfer the DACs’ setup and output
values from the digital source. The serial protocol can
be interfaced to SPI™ or Microwire peripherals common on many microcontroller units (MCUs), including
Microchip’s PICmicro® MCUs and dsPIC® DSC family
of MCUs. In addition to the three serial connections
(CS, SCK and SDI), the LDAC signal synchronizes
when the serial settings are latched into the DAC’s
output from the serial input latch. Figure 6-1 illustrates
the required connections. Note that LDAC is active-low.
If desired, this input can be tied low to reduce the
required connections from 4 to 3. Write commands will
be latched directly into the output latch when a valid 16
clock transmission has been received and CS has
been raised.
6.2
Power Supply Considerations
The typical application will require a bypass capacitor
in order to filter high-frequency noise. The noise can be
induced onto the power supply's traces or as a result of
changes on the DAC's output. The bypass capacitor
helps to minimize the effect of these noise sources on
signal integrity. Figure 6-1 illustrates an appropriate
bypass strategy.
In this example, the recommended bypass capacitor
value is 0.1 µF. This capacitor should be placed as
close to the device power pin (VDD) as possible (within
4 mm).
The power source supplying these devices should be
as clean as possible. If the application circuit has separate digital and analog power supplies, AVDD and
AVSS should reside on the analog plane.
VDD
VDD
0.1 µF 0.1 µF
VDD
VOUTA
0.1 µF
1 µF
VOUTB
VOUTA
1 µF
VOUTB
SDI
CS1
SDI
AVSS
SDO
SCK
LDAC
CS0
AVSS
FIGURE 6-1:
Diagram.
6.4
PICmicro® Microcontroller
6.1
MCP482X
Set Point or Offset Trimming
Sensor Calibration
Precision Selectable Voltage Reference
Portable Instrumentation (Battery-Powered)
Calibration of Optical Communication Devices
MCP482X
•
•
•
•
•
AVSS
Typical Connection
Layout Considerations
Inductively-coupled AC transients and digital switching
noise can degrade the output signal integrity,
potentially
masking
the
MCP482X
family’s
performance. Careful board layout will minimize these
effects and increase the Signal-to-Noise Ratio (SNR).
Bench testing has shown that a multi-layer board
utilizing a low-inductance ground plane, isolated inputs,
isolated outputs and proper decoupling are critical to
achieving the performance that the MCP482X devices
are capable of providing. Particularly harsh
environments may require shielding of critical signals.
Breadboards and wire-wrapped boards are not
recommended if low noise is desired.
© 2005 Microchip Technology Inc.
DS21953A-page 19
MCP4821/MCP4822
6.5
6.5.1.1
Single-Supply Operation
If the application is calibrating the threshold of a diode,
transistor or resistor tied to AVSS, a threshold range of
0.8V may be desired to provide 200 µV resolution. Two
common methods to achieve a 0.8V range is to either
reduce VREF to 0.82V (would require MCP492X device
and external voltage reference) or use a voltage divider
on the DAC’s output. Typically, when using a lowvoltage VREF, the noise floor causes SNR error that is
intolerable. The voltage divider method provides some
advantages when VREF needs to be very low or when
the desired output voltage is not available. Using two
resistors to scale the output range down to the precise
desired level is a simple, low-cost method to achieve
very small step sizes. Example 6-1 illustrates this
concept. Note that the bypass capacitor on the output
of the voltage divider plays a critical function in
attenuating the output noise of the DAC and the
induced noise from the environment.
The MCP482X devices are Rail-to-Rail (R-R) input and
output DACs designed to operate with a VDD range of
2.7V to 5.5V. Its output amplifier is robust enough to
drive common, small-signal loads directly, thus eliminating the cost and size of an external buffer for most
applications.
6.5.1
Decreasing The Output Step Size
DC SET POINT OR CALIBRATION
A common application for a DAC with the MCP482X
family’s performance is a digitally-controlled set point
and/or calibration of variable parameters, such as sensor offset or slope. 12-bit resolution provides 4096 output steps. If G = 1 is selected, then the internal 2.048
VREF would produce 500 µV of resolution. If G = 2 is
selected, the internal 2.048 VREF would produce 1 mV
of resolution.
The MCP482X family’s low ±0.75 (max.) DNL
performance is critical to meeting calibration accuracy
in production.
VDD
VCC+
RSENSE
VDD
MCP482X
VOUT
Comparator
R1
VTRIP
R2
0.1 uF
VCC–
SPI™
3
D
V OUT = 2.048 ⋅ G --------12
2
⎛ R2 ⎞
V trip = VOUT ⎜ --------------------⎟
⎝ R 1 + R 2⎠
EXAMPLE 6-1:
DS21953A-page 20
G = Gain select (1x or 2x)
D = Digital value of DAC (0 – 4096)
Set Point or Threshold Calibration.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
6.5.1.2
Building a “Window” DAC
creating a “window” around the threshold has several
advantages. One simple method to create this
“window” is to use a voltage divider network with a pullup and pull-down resistor. Example 6-2 and
Example 6-4 illustrates this concept.
When calibrating a set point or threshold of a sensor,
rarely does the sensor utilize the entire output range of
the DAC. If the LSb size is adequate to meet the application’s accuracy needs, the resolution is sacrificed
without consequences. If greater accuracy is needed,
then the output range will need to be reduced to
increase the resolution around the desired threshold. If
the threshold is not near VREF, 2VREF or AVSS, then
VCC+
The MCP482X family’s low ±0.75 (max.) DNL
performance is critical to meet calibration accuracy in
production.
VCC+
RSENSE
VDD
MCP482X
VOUT
R3
R1
VTRIP
R2
0.1 µF
Comparator
VCC-
SPI™
3
VCCD
V OUT = 2.048 ⋅ G ------12
2
Thevenin
Equivalent
R2R3
R 23 = -----------------R2 + R 3
V 23
R1
VOUT
VO
( V CC+ R 2 ) + ( VCC- R 3 )
= -----------------------------------------------------R 2 + R3
V OUT R23 + V 23 R 1
V trip = -------------------------------------------R 2 + R 23
EXAMPLE 6-2:
G = Gain select (1x or 2x)
D = Digital value of DAC (0 – 4096)
R23
V23
Single-Supply “Window” DAC.
© 2005 Microchip Technology Inc.
DS21953A-page 21
MCP4821/MCP4822
6.6
Bipolar Operation
Example 6-3 illustrates a simple bipolar voltage source
configuration. R1 and R2 allow the gain to be selected,
while R3 and R4 shift the DAC's output to a selected
offset. Note that R4 can be tied to VDD, instead of AVSS,
if a higher offset is desired. Note that a pull-up to VDD
could be used, instead of R4 or in addition to R4, if a
higher offset is desired.
Bipolar operation is achievable using the MCP482X
devices by using an external operational amplifier (op
amp). This configuration is desirable due to the wide
variety and availability of op amps. This allows a general purpose DAC, with its cost and availability advantages, to meet almost any desired output voltage
range, power and noise performance.
R2
VDD
VDD
VCC+
R1
VOUT
R3
VO
VIN+
MCP482X
VCC–
0.1 µF
R4
SPI™
3
D
V OUT = 2.048 ⋅ G ------12
2
V OUT R4
VIN+ = -------------------R3 + R 4
R2
R2
VO = V IN+ ⎛ 1 + ------⎞ – V DD ⎛ ------⎞
⎝ R 1⎠
⎝
R 1⎠
EXAMPLE 6-3:
6.6.1
Digitally-Controlled Bipolar Voltage Source.
DESIGN A BIPOLAR DAC USING
EXAMPLE 6-3
An output step magnitude of 1 mV, with an output range
of ±2.05V, is desired for a particular application.
1.
2.
G = Gain select (1x or 2x)
D = Digital value of DAC (0 – 4096)
Calculate the range: +2.05V – (-2.05V) = 4.1V.
Calculate the resolution needed:
4.1V/1 mV = 4100
4.
Next, solve for R3 and R4 by setting the DAC to
4096, knowing that the output needs to be
+2.05V.
R4
2.05V + ( 0.5 ⋅ 4.096V )
2
---------------------- = ------------------------------------------------------- = --( R 3 + R4 )
1.5 ⋅ 4.096V
3
If R4 = 20 kΩ, then R3 = 10 kΩ
Since 212 = 4096, 12-bit resolution is desired.
3.
The amplifier gain (R2/R1), multiplied by fullscale VOUT (4.096V), must be equal to the
desired minimum output to achieve bipolar
operation. Since any gain can be realized by
choosing resistor values (R1+R2), the VREF
value must be selected first. If a VREF of 4.096V
is used (G=2), solve for the amplifier’s gain by
setting the DAC to 0, knowing that the output
needs to be -2.05V. The equation can be
simplified to:
–R2
– 2.05
--------- = ----------------R1
4.096V
R
1
-----2- = --2
R1
If R1 = 20 kΩ and R2 = 10 kΩ, the gain will be 0.5
DS21953A-page 22
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
6.7
Selectable Gain and Offset Bipolar
Voltage Output Using A Dual DAC
In some applications, precision digital control of the
output range is desirable. Example 6-4 illustrates how
to use the MCP482X family to achieve this in a bipolar
or single-supply application.
This circuit is typically used for linearizing a sensor
whose slope and offset varies.
The equation to design a bipolar “window” DAC would
be utilized if R3, R4 and R5 are populated.
R2
VDD
VOUTA
VCC+
R1
MCP482X
VDD
DACA (Gain Adjust)
VOUTB
VCC+
VO
R5
R3
MCP482X
DACB (Offset Adjust)
SPI™
R4
3
0.1 µF
VCC–
VCC–
DB
V OUTB = ( 2.048V ⋅ G B ) ------12
2
DA
V OUTA = ( 2.048V ⋅ G A ) ------12
2
AVSS = GND
VOUTB R 4 + VCC- R3
VIN+ = -----------------------------------------------R3 + R 4
G = Gain select (1x or 2x)
R2
R2
V O = V IN+ ⎛ 1 + ------⎞ – VOUTA ⎛ ------⎞
⎝ R 1⎠
⎝
R 1⎠
D = Digital value of DAC (0 – 4096)
Offset Adjust Gain Adjust
Bipolar “Window” DAC using R4 and R5
Thevenin
Equivalent
V CC+ R 4 + VCC- R5
V45 = -------------------------------------------R 4 + R5
V OUTB R45 + V 45 R 3
V IN+ = ----------------------------------------------R 3 + R 45
R4 R5
R 45 = -----------------R4 + R5
R2
R2
V O = VIN+ ⎛⎝ 1 + ------⎞⎠ – V OUTA ⎛⎝ ------⎞⎠
R1
R1
Offset Adjust Gain Adjust
EXAMPLE 6-4:
Bipolar Voltage Source with Selectable Gain and Offset.
© 2005 Microchip Technology Inc.
DS21953A-page 23
MCP4821/MCP4822
6.8
Designing A Double-Precision
DAC Using A Dual DAC
1.
Example 6-5 illustrates how to design a single-supply
voltage output capable of up to 24-bit resolution from a
dual 12-bit DAC. This design is simply a voltage divider
with a buffered output.
2.
As an example, if a similar application to the one
developed in Section 6.6.1 “Design a Bipolar DAC
Using Example 6-3” required a resolution of 1 µV
instead of 1 mV, and a range of 0V to 4.1V, then 12-bit
resolution would not be adequate.
3.
4.
Calculate the resolution needed:
4.1V/1 µV = 4.1e06. Since 222 = 4.2e06, 22-bit
resolution is desired. Since DNL = ±0.75 LSb,
this design can be attempted with the MCP482X
family.
Since DACB‘s VOUTB has a resolution of 1 mV,
its output only needs to be “pulled” 1/1000 to
meet the 1 µV target. Dividing VOUTA by 1000
would allow the application to compensate for
DACB‘s DNL error.
If R2 is 100Ω, then R1 needs to be 100 kΩ.
The resulting transfer function is shown in the
equation of Example 6-5.
VDD
MCP482X
VDD
MCP482X
VCC+
DACA (Fine Adjust)
VO
VOUTA
R1
R1 >> R2
VOUTB
R2
0.1 µF
VCC–
DACB (Course Adjust)
SPI™
3
DA
V OUTA = 2.048V ⋅ G A ------12
2
DB
VOUTB = 2.048V ⋅ G B ------12
2
G = Gain select (1x or 2x)
D = Digital value of DAC (0 – 4096)
V OUTA R2 + V OUTB R1
VO = ----------------------------------------------------R1 + R 2
EXAMPLE 6-5:
DS21953A-page 24
Simple, Double-Precision DAC.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
6.9
Building A Programmable Current
Source
Example 6-6 illustrates a variation on a voltage follower
design where a sense resistor is used to convert the
DAC’s voltage output into a digitally-selectable current
source.
Adding the resistor network from Example 6-2 would
be advantageous in this application. The smaller
RSENSE is, the less power dissipated across it.
However, this also reduces the resolution that the
current can be controlled with. The voltage divider, or
“window”, DAC configuration would allow the range to
be reduced, thus increasing resolution around the
range of interest. When working with very small sensor
voltages, plan on eliminating the amplifier's offset error
by storing the DAC's setting under known sensor
conditions.
VDD
MCP482X
VOUT
VCC+
Load
IL
VCC– Ib
SPI™
3
Rsense
V OUT
D
= 2.048V ⋅ G ------12
2
IL
I b = ---β
V OUT
β
I L = --------------- × -----------Rsense β + 1
G = Gain select (1x or 2x)
D = Digital value of DAC (0 – 4096)
EXAMPLE 6-6:
Digitally-Controlled Current
Source.
© 2005 Microchip Technology Inc.
DS21953A-page 25
MCP4821/MCP4822
7.0
DEVELOPMENT SUPPORT
7.1
Evaluation & Demonstration
Boards
The Mixed Signal PICtail™ Demo Board supports the
MCP482X
family
of
devices.
Refer
to
www.microchip.com for further information on this
product’s capabilities and availability.
DS21953A-page 26
7.2
Application Notes
Application notes illustrating the performance and
implementation of the MCP482X family are planned but
are
currently
not
released.
Refer
to
www.microchip.com for further information.
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
8.0
PACKAGING INFORMATION
8.1
Package Marking Information
Example:
8-Lead MSOP
XXXXXX
YWWNNN
8-Lead PDIP (300 mil)
XXXXXXXX
XXXXXNNN
YYWW
Legend: XX...X
Y
YY
WW
NNN
e3
*
Note:
Example:
MCP4821
E/P e^3 256
0524
8-Lead SOIC (150 mil)
XXXXXXXX
XXXXYYWW
NNN
4821E
524256
Example:
MCP4821E
e3 0524
SN^^
256
Customer-specific information
Year code (last digit of calendar year)
Year code (last 2 digits of calendar year)
Week code (week of January 1 is week ‘01’)
Alphanumeric traceability code
Pb-free JEDEC designator for Matte Tin (Sn)
This package is Pb-free. The Pb-free JEDEC designator ( e3 )
can be found on the outer packaging for this package.
In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line, thus limiting the number of available
characters for customer-specific information.
© 2005 Microchip Technology Inc.
DS21953A-page 27
MCP4821/MCP4822
8-Lead Plastic Micro Small Outline Package (MS) (MSOP)
E
E1
p
D
2
B
n
1
α
A2
A
c
φ
A1
(F)
L
β
Units
Dimension Limits
n
p
MIN
INCHES
NOM
MAX
MILLIMETERS*
NOM
8
0.65 BSC
0.75
0.85
0.00
4.90 BSC
3.00 BSC
3.00 BSC
0.40
0.60
0.95 REF
0°
0.08
0.22
5°
5°
-
MIN
8
Number of Pins
.026 BSC
Pitch
A
.043
Overall Height
A2
.030
.033
.037
Molded Package Thickness
.006
.000
A1
Standoff
E
.193 TYP.
Overall Width
E1
.118 BSC
Molded Package Width
.118 BSC
D
Overall Length
L
.016
.024
.031
Foot Length
Footprint (Reference)
F
.037 REF
φ
Foot Angle
0°
8°
c
Lead Thickness
.003
.006
.009
.009
.012
.016
Lead Width
B
α
Mold Draft Angle Top
5°5°
15°
β
5°5°
15°
Mold Draft Angle Bottom
*Controlling Parameter
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not
exceed .010" (0.254mm) per side.
MAX
1.10
0.95
0.15
0.80
8°
0.23
0.40
15°
15°
JEDEC Equivalent: MO-187
Drawing No. C04-111
DS21953A-page 28
© 2005 Microchip Technology Inc.
MCP4821/MCP4822
8-Lead Plastic Dual In-line (P) – 300 mil (PDIP)
E1
D
2
n
1
α
E
A2
A
L
c
A1
β
B1
p
eB
B
Units
Dimension Limits
n
p
Number of Pins
Pitch
Top to Seating Plane
Molded Package Thickness
Base to Seating Plane
Shoulder to Shoulder Width
Molded Package Width
Overall Length
Tip to Seating Plane
Lead Thickness
Upper Lead Width
Lower Lead Width
Overall Row Spacing
Mold Draft Angle Top
Mold Draft Angle Bottom
* Controlling Parameter
§ Significant Characteristic
§
A
A2
A1
E
E1
D
L
c
B1
B
eB
α
β
MIN
.140
.115
.015
.300
.240
.360
.125
.008
.045
.014
.310
5
5
INCHES*
NOM
MAX
8
.100
.155
.130
.170
.145
.313
.250
.373
.130
.012
.058
.018
.370
10
10
.325
.260
.385
.135
.015
.070
.022
.430
15
15
MILLIMETERS
NOM
8
2.54
3.56
3.94
2.92
3.30
0.38
7.62
7.94
6.10
6.35
9.14
9.46
3.18
3.30
0.20
0.29
1.14
1.46
0.36
0.46
7.87
9.40
5
10
5
10
MIN
MAX
4.32
3.68
8.26
6.60
9.78
3.43
0.38
1.78
0.56
10.92
15
15
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed
.010” (0.254mm) per side.
JEDEC Equivalent: MS-001
Drawing No. C04-018
© 2005 Microchip Technology Inc.
DS21953A-page 29
MCP4821/MCP4822
8-Lead Plastic Small Outline (SN) – Narrow, 150 mil (SOIC)
E
E1
p
D
2
B
n
1
h
α
45°
c
A2
A
φ
β
L
Units
Dimension Limits
n
p
Number of Pins
Pitch
Overall Height
Molded Package Thickness
Standoff §
Overall Width
Molded Package Width
Overall Length
Chamfer Distance
Foot Length
Foot Angle
Lead Thickness
Lead Width
Mold Draft Angle Top
Mold Draft Angle Bottom
* Controlling Parameter
§ Significant Characteristic
A
A2
A1
E
E1
D
h
L
φ
c
B
α
β
MIN
.053
.052
.004
.228
.146
.189
.010
.019
0
.008
.013
0
0
A1
INCHES*
NOM
8
.050
.061
.056
.007
.237
.154
.193
.015
.025
4
.009
.017
12
12
MAX
.069
.061
.010
.244
.157
.197
.020
.030
8
.010
.020
15
15
MILLIMETERS
NOM
8
1.27
1.35
1.55
1.32
1.42
0.10
0.18
5.79
6.02
3.71
3.91
4.80
4.90
0.25
0.38
0.48
0.62
0
4
0.20
0.23
0.33
0.42
0
12
0
12
MIN
MAX
1.75
1.55
0.25
6.20
3.99
5.00
0.51
0.76
8
0.25
0.51
15
15
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed
.010” (0.254mm) per side.
JEDEC Equivalent: MS-012
Drawing No. C04-057
DS21953A-page 30
© 2005 Microchip Technology Inc.
MCP4821/4822
APPENDIX A:
REVISION HISTORY
Revision A (June 2005)
• Original Release of this Document.
© 2005 Microchip Technology Inc.
DS21953A-page 31
MCP4821/4822
NOTES:
DS21953A-page 32
© 2005 Microchip Technology Inc.
MCP4821/4822
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO.
X
/XX
Device
Temperature
Range
Package
Examples:
a)
b)
Device:
MCP4821:
MCP4821T:
MCP4822:
MCP4822T:
12-Bit DAC with SPI™ Interface
12-Bit DAC with SPI Interface
(Tape and Reel) (SOIC, MSOP)
12-Bit DAC with SPI Interface
12-Bit DAC with SPI Interface
(Tape and Reel) (SOIC, MSOP)
Temperature Range:
E
= -40°C to +125°C
Package:
MS = Plastic MSOP, 8-lead
P
= Plastic DIP (300 mil Body), 8-lead
SN = Plastic SOIC, (150 mil Body), 8-lead
© 2005 Microchip Technology Inc.
c)
d)
e)
a)
b)
c)
MCP4821T-E/SN: Tape and Reel
Extended Temperature,
8LD SOIC package.
MCP4821T-E/MS: Tape and Reel
Extended Temperature,
8LD MSOP package.
MCP4821-E/SN:
Extended Temperature,
8LD SOIC package.
MCP4821-E/MS: Extended Temperature,
8LD MSOP package.
MCP4821-E/P:
Extended Temperature,
8LD PDIP package.
MCP4822T-E/SN: Tape and Reel
Extended Temperature,
8LD SOIC package.
MCP4822-E/P:
Extended Temperature,
8LD PDIP package.
MCP4822-E/SN:
Extended Temperature,
8LD SOIC package.
DS21953A-page 33
MCP4821/4822
NOTES:
DS21953A-page 34
© 2005 Microchip Technology Inc.
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED,
WRITTEN OR ORAL, STATUTORY OR OTHERWISE,
RELATED TO THE INFORMATION, INCLUDING BUT NOT
LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANTABILITY OR FITNESS FOR PURPOSE.
Microchip disclaims all liability arising from this information and
its use. Use of Microchip’s products as critical components in
life support systems is not authorized except with express
written approval by Microchip. No licenses are conveyed,
implicitly or otherwise, under any Microchip intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro,
PICSTART, PRO MATE, PowerSmart, rfPIC, and
SmartShunt are registered trademarks of Microchip
Technology Incorporated in the U.S.A. and other countries.
AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB,
PICMASTER, SEEVAL, SmartSensor and The Embedded
Control Solutions Company are registered trademarks of
Microchip Technology Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, dsPICDEM,
dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR,
FanSense, FlexROM, fuzzyLAB, In-Circuit Serial
Programming, ICSP, ICEPIC, Linear Active Thermistor,
MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM,
PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo,
PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode,
Smart Serial, SmartTel, Total Endurance and WiperLock are
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2005, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received ISO/TS-16949:2002 quality system certification for
its worldwide headquarters, design and wafer fabrication facilities in
Chandler and Tempe, Arizona and Mountain View, California in
October 2003. The Company’s quality system processes and
procedures are for its PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
© 2005 Microchip Technology Inc.
DS21953A-page 35
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04/20/05
DS21953A-page 36
© 2005 Microchip Technology Inc.
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