LINER LTC1821ACGW 16-bit, ultra precise, fast settling vout dac Datasheet

LTC1821
16-Bit, Ultra Precise,
Fast Settling VOUT DAC
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FEATURES
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DESCRIPTIO
The LTC®1821 is a parallel input 16-bit multiplying voltage
output DAC that operates from analog supply voltages of
±5V up to ±15V. INL and DNL are accurate to 1LSB over the
industrial temperature range in both unipolar 0V to 10V and
bipolar ±10V modes. Precise 16-bit bipolar ±10V outputs are
achieved with on-chip 4-quadrant multiplication resistors.
The LTC1821 is available in a 36-lead SSOP package and is
specified over the industrial temperature range.
2µs Settling to 0.0015% for 10V Step
1LSB Max DNL and INL Over Industrial
Temperature Range
On-Chip 4-Quadrant Resistors Allow Precise 0V to
10V, 0V to –10V or ±10V Outputs
Low Glitch Impulse: 2nV•s
Low Noise: 13nV/√Hz
36-Lead SSOP Package
Power-On Reset
Asynchronous Clear Pin
LTC1821: Reset to Zero Scale
LTC1821-1: Reset to Midscale
The device includes an internal deglitcher circuit that reduces
the glitch impulse to less than 2nV•s (typ). The LTC1821
settles to 1LBS in 2µs with a full-scale 10V step. The
combination of fast, precise settling and ultra low glitch make
the LTC1821 ideal for precision industrial control applications.
The asynchronous CLR pin resets the LTC1821 to zero scale
and resets the LTC1821-1 to midscale.
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APPLICATIO S
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Process Control and Industrial Automation
Precision Instrumentation
Direct Digital Waveform Generation
Software-Controlled Gain Adjustment
Automatic Test Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
16-Bit, 4-Quadrant Multiplying DAC with a
Minimum of External Components
VREF
3
+
0.1µF
6
LT®1468
2
LTC1821/LTC1821-1
Integral Nonlinearity
5V
1.0
–
10
R1
9
RCOM
8
REF
2
VCC
11
12
14
ROFS
RFB
IOUT
V+
R1
ROFS
R2
16
DATA
INPUTS
LTC1821-1
RFB
WR
LD
CLR
7
13
16-BIT DAC
DNC* DNC* DNC* NC
18
19
21
22
15V
0.1µF
+
VOUT
V
24 23
15
–
3 TO 6,
25 TO 36
WR LD CLR
VREF = 10V
VOUT = ±10V BIPOLAR
0.8
15pF
15pF
DGND
1
–
20
VREF
VOUT =
–VREF
–15V
0.1µF
AGNDF AGNDS
17
16
INTEGRAL NONLINEARITY (LSB)
–VREF
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
0
49152
32768
16384
DIGITAL INPUT CODE
65535
1821 TA02
1821 TA01
*DO NOT CONNECT
1
LTC1821
W
U
U
U
W W
W
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
ORDER PART
NUMBER
TOP VIEW
VCC to AGNDF, AGNDS ............................... – 0.3V to 7V
VCC to DGND .............................................. – 0.3V to 7V
Total Supply Voltage (V+ to V–) ............................... 36V
AGNDF, AGNDS to DGND ............................. VCC + 0.3V
DGND to AGNDF, AGNDS ............................. VCC + 0.3V
REF, RCOM to AGNDF, AGNDS, DGND .................. ±15V
ROFS, RFB, R1, to AGNDF, AGNDS, DGND ............ ±15V
Digital Inputs to DGND ............... – 0.3V to (VCC + 0.3V)
IOUT to AGNDF, AGNDS............... – 0.3V to (VCC + 0.3V)
Maximum Junction Temperature .......................... 150°C
Operating Temperature Range
LTC1821C/LTC1821-1C .......................... 0°C to 70°C
LTC1821I/LTC1821-1I ....................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
DGND
1
36 D4
VCC
2
35 D5
D3
3
34 D6
D2
4
33 D7
D1
5
32 D8
D0
6
31 D9
CLR
7
30 D10
REF
8
29 D11
RCOM
9
28 D12
R1 10
27 D13
ROFS 11
26 D14
RFB 12
25 D15
VOUT 13
24 WR
IOUT 14
23 LD
V+ 15
22 NC
AGNDS 16
21 DNC*
AGNDF 17
20 V –
DNC* 18
LTC1821ACGW
LTC1821BCGW
LTC1821-1ACGW
LTC1821-1BCGW
LTC1821AIGW
LTC1821BIGW
LTC1821-1AIGW
LTC1821-1BIGW
19 DNC*
GW PACKAGE
36-LEAD PLASTIC SSOP WIDE
TJMAX = 125°C, θJA = 80°C/ W
*DO NOT CONNECT
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = TMIN to TMAX,
V+ = 15V, V– = –15V, VCC = 5V, VREF = 10V, AGNDF = AGNDS = DGND = 0V.
SYMBOL PARAMETER
LTC1821B/-1B
MIN
TYP
MAX
CONDITIONS
LTC1821A/-1A
MIN
TYP MAX
UNITS
Accuracy
Resolution
Monotonicity
INL
DNL
GE
2
16
●
16
16
Bits
16
Bits
●
±2
±2
±0.25
±0.35
±1
±1
LSB
LSB
TA = 25°C
TMIN to TMAX
●
±1
±1
±0.2
±0.2
±1
±1
LSB
LSB
Unipolar Mode
TA = 25°C (Note 3)
TMIN to TMAX
●
±16
±24
±5
±8
±16
±16
LSB
LSB
Bipolar Mode
TA = 25°C (Note 3)
TMIN to TMAX
●
± 16
± 24
±2
±5
±16
±16
LSB
LSB
Gain Temperature Coefficient
∆Gain/∆Temperature (Note 4)
●
3
1
3
ppm/°C
Unipolar Zero-Scale Error
TA = 25°C
TMIN to TMAX
●
±3
±6
±0.25
±0.50
±2
±4
LSB
LSB
TA = 25°C
TMIN to TMAX
●
±12
±16
±2
±3
±8
±10
LSB
LSB
VCC = 5V ±10%
V+, V – = ±4.5V to ±16.5V
●
●
2
±2
0.7
±0.1
2
±2
LSB/V
LSB/V
Integral Nonlinearity
Differential Nonlinearity
Gain Error
Bipolar Zero Error
PSRR
●
Power Supply Rejection Ratio
TA = 25°C (Note 2)
TMIN to TMAX
1
LTC1821
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = TMIN to TMAX,
V + = 15V, V – = – 15V, VCC = 5V, VREF = 10V, AGNDF = AGNDS = DGND = 0V.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Input
RREF
DAC Input Resistance (Unipolar)
(Note 6)
●
4.5
6
10
kΩ
R1/R2
R1/R2 Resistance (Bipolar)
(Notes 6, 11)
●
9
12
20
kΩ
ROFS, RFB
Feedback and Offset Resistances
(Note 6)
●
9
12
20
kΩ
AC Performance (Note 4)
Output Voltage Settling Time
∆VOUT = 10V (Notes 7, 8)
2
µs
Midscale Glitch Impulse
(Note 10)
2
nV•s
Digital-Feedthrough
(Note 9)
2
nV•s
Multiplying Feedthrough Error
VREF = ±10V, 10kHz Sine Wave (Note 7)
1
mVP-P
Multiplying Bandwidth
Code = Full Scale (Note 7)
600
kHz
Output Noise Voltage Density
1kHz to 100kHz (Note 7)
Code = Zero Scale
Code = Full Scale
13
20
nV/√Hz
nV/√Hz
0.45
1
µVRMS
µVRMS
Output Noise Voltage
1/f Noise Corner
0.1Hz to 10Hz (Note 7)
Code = Zero Scale
Code = Full Scale
(Note 7)
30
Hz
Analog Outputs (Note 4)
VOUT
ISC
SR
DAC Output Swing
RL = 2k, V + = 15V, V – = –15V
RL = 2k, V + = 5V, V – = –5V
●
●
DAC Output Load Regulation
V + = 15V, V – = –15V, ±5mA Load
●
Short-Circuit Current
VOUT = 0V, V + = 15V, V – = –15V
●
Slew Rate
RL = 2k, V + = 15V, V – = –15V
RL = 2k, V + = 5V, V – = –5V
±12.6
±2.6
V
V
0.02
12
0.2
LSB/mA
40
mA
20
14
V/µs
V/µs
Digital Inputs
VIH
Digital Input High Voltage
●
VIL
Digital Input Low Voltage
●
IIN
Digital Input Current
●
CIN
Digital Input Capacitance
(Note 4 ) VIN = 0V
2.4
V
0.001
●
0.8
V
±1
µA
8
pF
Timing Characteristics
t DS
Data to WR Setup Time
●
60
20
t DH
Data to WR Hold Time
t WR
WR Pulse Width
t LD
t CLR
t LWD
ns
●
0
–12
ns
●
60
25
ns
LD Pulse Width
●
110
55
ns
Clear Pulse Width
●
60
40
ns
WR to LD Delay Time
●
0
ns
Power Supply
ICC
Supply Current, VCC
Digital Inputs = 0V or VCC
●
1.5
10
µA
IS
Supply Current, V+, V –
±15V
±5V
●
●
4.5
4.0
7.0
6.8
mA
mA
VCC
Supply Voltage
●
5
5.5
V
V+
Supply Voltage
●
4.5
16.5
V
V–
Supply Voltage
●
–16.5
– 4.5
V
4.5
3
LTC1821
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: ±1LSB = ±0.0015% of full scale = ±15.3ppm of full scale.
Note 3: Using internal feedback resistor.
Note 4: Guaranteed by design, not subject to test.
Note 5: IOUT with DAC register loaded to all 0s.
Note 6: Typical temperature coefficient is 100ppm/°C.
Note 7: Measured in unipolar mode.
Note 8: To 0.0015% for a full-scale change, measured from the rising
edge of LD.
Note 9: REF = 0V. DAC register contents changed from all 0s to all 1s or all
1s to all 0s. LD low and WR high.
Note 10: Midscale transition code: 0111 1111 1111 1111 to
1000 0000 0000 0000. Unipolar mode, CFEEDBACK = 33pF.
Note 11: R1 and R2 are measured between R1 and RCOM, REF and RCOM.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Midscale Glitch Impulse
– 40
CFEEDBACK = 30pF
VREF = 10V
30
OUTPUT VOLTAGE (mV)
Full-Scale Setting Waveform
LD PULSE
5V/DIV
20
10
GATED
SETTLING
WAVEFORM
500µV/DIV
0
1nV-s TYPICAL
–10
–20
– 40
1821 G02
500ns/DIV
VREF = –10V
CFEEDBACK = 20pF
0V TO 10V STEP
– 30
0.2
0
0.4
0.6
TIME (µs)
0.8
SIGNAL/(NOISE + DISTORTION) (dB)
40
Unipolar Multiplying Mode
Signal-to-(Noise + Distortion)
vs Frequency
VCC = 5V
CFEEDBACK = 30pF
REFERENCE = 6VRMS
– 50
– 60
– 70
– 80
500kHz FILTER
– 90
80kHz FILTER
–100
30kHz FILTER
–110
10
1.0
100
1k
10k
FREQUENCY (Hz)
100k
1821 G03
1821 G01
Bipolar Multiplying Mode
Signal-to-(Noise + Distortion)
vs Frequency, Code = All Zeros
– 60
– 70
– 80
500kHz FILTER
– 90
–100
30kHz
FILTER
10
100
1k
10k
FREQUENCY (Hz)
VCC = 5V
ALL DIGITAL INPUTS
TIED TOGETHER
4
– 60
– 70
– 80
500kHz FILTER
– 90
3
2
1
80kHz FILTER
30kHz FILTER
0
–110
100k
1821 G04
4
5
VCC = 5V USING AN LT1468
CFEEDBACK = 15pF
REFERENCE = 6VRMS
–100
80kHz FILTER
–110
– 50
VCC Supply Current vs Digital
Input Voltage
SUPPLY CURRENT (mA)
– 50
– 40
VCC = 5V USING AN LT1468
CFEEDBACK = 15pF
REFERENCE = 6VRMS
SIGNAL/(NOISE + DISTORTION) (dB)
SIGNAL/(NOISE + DISTORTION) (dB)
– 40
Bipolar Multiplying Mode
Signal-to-(Noise + Distortion)
vs Frequency, Code = All Ones
10
100
1k
10k
FREQUENCY (Hz)
100k
1821 G05
0
1
3
2
INTPUT VOLTAGE (V)
4
5
1821 G06
LTC1821
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Logic Threshold vs VCC Supply
Voltage
Integral Nonlinearity (INL)
INTEGRAL NONLINEARITY (LSB)
LOGIC THRESHOLD (V)
2.5
2.0
1.5
1.0
0.5
Differential Nonlinearity (DNL)
1.0
1.0
0.8
0.8
DIFFERENTIAL NONLINEARITY (LSB)
3.0
0.6
0.4
0.2
0
– 0.2
– 0.4
– 0.6
– 0.8
0
1
5
2
3
4
SUPPLY VOLTAGE (V)
6
– 0.4
– 0.6
– 0.8
–1.0
0
7
49152
32768
16384
DIGITAL INPUT CODE
0.2
0
– 0.2
– 0.4
– 0.6
1.0
1.0
0.8
0.8
0.6
0.4
0.2
0
– 0.2
– 0.4
– 0.6
– 0.8
– 0.8
–1.0
–10 – 8 – 6 – 4 – 2 0 2 4 6
REFERENCE VOLTAGE (V)
–1.0
–10 – 8 – 6 – 4 – 2 0 2 4 6
REFERENCE VOLTAGE (V)
8
10
1821 G10
0.8
INTEGRAL NONLINEARITY (LSB)
1.0
0.8
0.2
0
– 0.2
– 0.4
– 0.6
–1.0
–10 – 8 – 6 – 4 – 2 0 2 4 6
REFERENCE VOLTAGE (V)
8
10
1821 G13
0
– 0.2
– 0.4
– 0.6
– 0.8
–1.0
–10 – 8 – 6 – 4 – 2 0 2 4 6
REFERENCE VOLTAGE (V)
10
8
10
1821 G12
Integral Nonlinearity vs VCC Supply
Voltage in Bipolar Mode
2.0
0.6
VREF = 10V
0.4
0.2
VREF = 2.5V
0
VREF = 10V
– 0.2
– 0.4
1.5
1.0
0.5
VREF = 10V
0
VREF = 2.5V
VREF = 10V
– 0.5
VREF = 2.5V
– 0.6
VREF = 2.5V
–1.0
–1.5
– 0.8
– 0.8
0.2
Integral Nonlinearity vs VCC Supply
Voltage in Unipolar Mode
1.0
0.4
0.6
0.4
1821 G11
Differential Nonlinearity vs
Reference Voltage in Bipolar Mode
0.6
8
65535
Differential Nonlinearity vs
Reference Voltage in Unipolar Mode
DIFFERENTIAL NONLINEARITY (LSB)
INTEGRAL NONLINEARITY (LSB)
0.8
0.4
49152
32768
16384
DIGITAL INPUT CODE
1821 G09
Integral Nonlinearity vs Reference
Voltage in Bipolar Mode
1.0
0.6
0
65535
1821 G08
Integral Nonlinearity vs Reference
Voltage in Unipolar Mode
INTEGRAL NONLINEARITY (LSB)
0
– 0.2
–1.0
1821 G07
DIFFERENTIAL NONLINEARITY (LSB)
0.4
0.2
INTEGRAL NONLINEARITY (LSB)
0
0.6
–1.0
2
3
4
5
6
SUPPLY VOLTAGE (V)
7
1821 G14
–2.0
2
3
4
5
6
SUPPLY VOLTAGE (V)
7
1821 G15
5
LTC1821
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Differential Nonlinearity vs VCC
Supply Voltage in Bipolar Mode
1.0
1.0
0.8
0.8
DIFFERENTIAL NONLINEARITY (LSB)
DIFFERENTIAL NONLINEARITY (LSB)
Differential Nonlinearity vs VCC
Supply Voltage in Unipolar Mode
0.6
0.4
VREF = 10V
VREF = 2.5V
0.2
0
– 0.2
VREF = 10V
VREF = 2.5V
– 0.4
– 0.6
– 0.8
–1.0
2
3
0.2
VREF = 10V
0
VREF = 2.5V
VREF = 10V
– 0.2
VREF = 2.5V
– 0.4
– 0.6
– 0.8
–1.0
7
4
5
6
SUPPLY VOLTAGE (V)
0.6
0.4
3
2
7
4
5
6
SUPPLY VOLTAGE (V)
1821 G16
Bipolar Multiplying Mode Frequency
Response vs Digital Code
– 40
– 60
– 80
– 100
– 20
ATTENUATION (dB)
ATTENUATION (dB)
– 20
0
ALL BITS ON
D15 ON
D14 ON
D13 ON
D12 ON
D11 ON
D10 ON
D9 ON
D8 ON
D7 ON
D6 ON
D5 ON
D4 ON
D3 ON
D2 ON
D1 ON
D0 ON
ALL BITS OFF
– 120
100
1k
– 40
– 60
– 80
10k
100k
FREQUENCY (Hz)
1M
– 20
CODES FROM
MIDSCALE
TO FULL SCALE
100
100k
1k
10k
FREQUENCY (Hz)
1M
10M
*DAC ZERO VOLTAGE OUTPUT LIMITED BY BIPOLAR
ZERO ERROR TO – 96dB TYPICAL (–78dB MAX, A GRADE)
VREF
3
30pF
8 9 10 11 12
14
LTC1821 13
1 16 17
VOUT
– 60
ALL BITS OFF
D14 ON
D14 AND D13 ON
D14 TO D12 ON
D14 TO D11 ON
D14 TO D10 ON
D14 TO D9 ON
D14 TO D8 ON
D14 TO D7 ON
D14 TO D6 ON
D14 TO D5 ON
D14 TO D4 ON
D14 TO D3 ON
D14 TO D2 ON
D14 TO D1 ON
CODES FROM
MIDSCALE
TO ZERO SCALE
D14 TO D0 ON
D15 ON*
– 100
100
10
100k
1k
10k
FREQUENCY (Hz)
1821 G19
1821 G18
VREF
– 40
– 80
D15 AND D1 ON
D15 AND D0 ON
D15 ON*
10
10M
0
ALL BITS ON
D15 AND D14 ON
D15 AND D13 ON
D15 AND D12 ON
D15 AND D11 ON
D15 AND D10 ON
D15 AND D9 ON
D15 AND D8 ON
D15 AND D7 ON
D15 AND D6 ON
D15 AND D5 ON
D15 AND D4 ON
D15 AND D3 ON
D15 AND D2 ON
– 100
Bipolar Multiplying Mode Frequency
Response vs Digital Code
ATTENUATION (dB)
Unipolar Multiplying Mode Frequency
Response vs Digital Code
0
1821 G17
1821 G20
*DAC ZERO VOLTAGE OUTPUT LIMITED BY BIPOLAR
ZERO ERROR TO – 96dB TYPICAL (–78dB MAX, A GRADE)
3
6
+
LT1468
–
2
12pF
12pF
6
15pF
9
8 11 12
LTC1821
1 16 17
6
10M
VREF
+
LT1468
–
2
12pF
12pF
10
1M
14
13
15pF
10
VOUT
9
8 11 12
LTC1821
1 16 17
14
13
VOUT
LTC1821
U
U
U
PIN FUNCTIONS
DGND (Pin 1): Digital Ground. Connect to analog ground.
VCC (Pin 2): Positive Supply Input. 4.5V ≤ VCC ≥ 5.5V.
Requires a bypass capacitor to ground.
D3 (Pin 3): Digital Input Data Bit 3.
D2 (Pin 4): Digital Input Data Bit 2.
D1 (Pin 5): Digital Input Data Bit 1.
D0 (Pin 6): LSB or Digital Input Data Bit 0.
CLR (Pin 7): Digital Clear Control Function for the DAC.
When CLR is taken to a logic low, it sets the DAC output
and all internal registers to: zero code for the LTC1821 and
midscale code for the LTC1821-1.
REF (Pin 8): Reference Input and 4-Quadrant Resistor R2.
Typically ±10V, accepts up to ±15V. In 2-quadrant mode,
tie this pin to the external reference signal. In 4-quadrant
mode, this pin is driven by external inverting reference
amplifier.
RCOM (Pin 9): Center Tap Point of the Two 4-Quadrant
Resistors R1 and R2. Normally tied to the inverting input
of an external amplifier in 4-quadrant operation. Otherwise this pin is shorted to the REF pin. See Figures 1
and 2.
IOUT (Pin 14): DAC Current Output. Normally tied through
a 22pF feedback capacitor in unipolar mode (15pF in
bipolar mode) to VOUT.
V + (Pin 15): Amplifier Positive Supply. Range is 4.5V to
16.5V.
AGNDS (Pin 16): Analog Ground Sense. Connect to
analog ground.
AGNDF (Pin 17): Analog Ground Force. Connect to
analog ground.
DNC (Pin 18, 19, 21): Connected internally. Do not
connect external circuitry to these pins.
V – (Pin 20): Amplifier Negative Supply. Range is – 4.5V
to – 16.5V.
NC (Pin 22): No Connection.
LD (Pin 23): DAC Digital Input Load Control Input. When
LD is taken to a logic high, data is loaded from the input
register into the DAC register, updating the DAC output.
WR (Pin 24): DAC Digital Write Control Input. When WR
is taken to a logic low, data is written from the digital input
pins into the 16-bit wide input reigster.
D15 (Pins 25): MSB or Digital Input Data Bit 15.
R1 (Pin 10): 4-Quadrant Resistor R1. In 2-quadrant
operation, short this pin to the REF pin. In 4-quadrant
mode, tie this pin to the external reference signal.
D14 (Pin 26): Digital Input Data Bit 14.
ROFS (Pin 11): Bipolar Offset Resistor. Typically swings
±10V, accepts up to ±15V. For 2-quadrant operation, tie
this pin to RFB and for 4-quadrant operation, tie this pin to
R1.
D12 (Pin 28): Digital Input Data Bit 12.
RFB (Pin12): Feedback Resistor. Normally connected to
VOUT. Typically swings ±10V. The voltage at this pin
swings 0 to VREF in unipolar mode and ±VREF in bipolar
mode.
VOUT (Pin 13): DAC Voltage Output. Normally connected
to RFB and to IOUT through a 22pF feedback capacitor in
unipolar mode (15pF in bipolar mode). Typically swings
±10V.
D13 (Pin 27): Digital Input Data Bit 13.
D11 (Pin 29): Digital Input Data Bit 11.
D10 (Pin 30): Digital Input Data Bit 10.
D9 (Pin 31): Digital Input Data Bit 9.
D8 (Pin 32): Digital Input Data Bit 8.
D7 (Pin 33): Digital Input Data Bit 7.
D6 (Pin 34): Digital Input Data Bit 6.
D5 (Pin 35): Digital Input Data Bit 5.
D4 (Pin 36): Digital Input Data Bit 4.
7
LTC1821
TRUTH TABLE
Table 1
CONTROL INPUTS
CLR WR LD
REGISTER OPERATION
0
X
X
Reset Input and DAC Register to All 0s for LTC1821 and Midscale for LTC1821-1 (Asynchronous Operation)
1
0
0
Write Input Register with All 16 Data Bits
1
1
1
Load DAC Register with the Contents of the Input Register
1
0
1
1
Input and DAC Register Are Transparent
CLK = LD and WR Tied Together. The 16 Data Bits Are Written Into the Input Register on the Falling Edge of the CLK and Then
Loaded Into the DAC Register on the Rising Edge of the CLK
1
1
0
No Register Operation
W
BLOCK DIAGRA
48k
REF
48k
12 RFB
8
12k
48k
RCOM 9
48k
48k
48k
48k
48k
48k
96k
96k
96k
96k
12k
12k
11 ROFS
12k
14 IOUT
R1 10
15 V +
–
+
VCC 2
13 VOUT
20 V –
DECODER
16 AGNDS
LD 23
LOAD
D15
(MSB)
D14
D13
D12
D11
•••
DAC REGISTER
17 AGNDF
D0
(LSB) RST
7 CLR
18 DNC*
19 DNC*
21 DNC*
WR 24
8
INPUT REGISTER
WR
25
26
D15
D14
••••
RST
36
3
4
5
6
D4
D3
D2
D1
D0
22 NC
*CONNECTED INTERNALLY.
DO NOT CONNECT EXTERNAL
CIRCUITRY TO THESE PINS
1 DGND
1821 BD
LTC1821
WU
W
TI I G DIAGRA
tWR
WR
DATA
tDS
tDH
tLWD
LD
tLD
tCLR
CLR
1821 TD
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W
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APPLICATIONS INFORMATION
Description
The LTC1821 is a 16-bit voltage output DAC with a full
parallel 16-bit digital interface. The device can operate
from 5V and ±15 supplies and provides both unipolar 0V
to – 10V or 0V to 10V and bipolar ±10V output ranges from
a 10V or –10V reference input. Additionally, the power
supplies for the LTC1821 can go as low as 4.5V and ±4.5V.
In this case for a 2.5V or – 2.5V reference, the output range
is 0V to – 2.5V, 0V to 2.5V and ±2.5V. The LTC1821 has
three additional precision resistors on chip for bipolar
operation. Refer to the block diagram regarding the following description.
The 16-bit DAC consists of a precision R-2R ladder for the
13 LSBs. The three MSBs are decoded into seven segments of resistor value R. Each of these segments and the
R-2R ladder carries an equally weighted current of one
eighth of full scale. The feedback resistor RFB and
4-quadrant resistor ROFS have a value of R/4. 4-quadrant
resistors R1 and R2 have a magnitude of R/4. R1 and R2
together with an external op amp (see Figure 2) inverts the
reference input voltage and applies it to the 16-bit DAC
input REF, in 4-quadrant operation. The REF pin presents
a constant input impedance of R/8 in unipolar mode and
R/12 in bipolar mode.
The LTC1821 contains an onboard precision high speed
amplifier. This amplifier together with the feedback resistor (RFB) form a precision current-to-voltage converter for
the DAC’s current output. The amplifier has very low noise,
offset, input bias current and settles in less than 2µs to
0.0015% for a 10V step. It can sink and source 22mA
(±15V) typically and can drive a 300pF capacitive load. An
added feature of these devices, especially for waveform
generation, is a proprietary deglitcher that reduces glitch
impulse to below 2nV-s over the DAC output voltage range.
Digital Section
The LTC1821 has a 16-bit wide full parallel data bus input.
The device is double-buffered with two 16-bit registers.
The double-buffered feature permits the update of several
DACs simultaneously. The input register is loaded directly
from a 16-bit microprocessor bus when the WR pin is
brought to a logic low level. The second register (DAC
register) is updated with the data from the input register
when the LD signal is brought to a logic high. Updating the
DAC register updates the DAC output with the new data. To
make both registers transparent in flowthrough mode, tie
WR low and LD high. However, this defeats the deglitcher
operation and output glitch impulse may increase. The
deglitcher is activated on the rising edge of the LD pin. The
9
LTC1821
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W
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APPLICATIONS INFORMATION
versatility of the interface also allows the use of the input
and DAC registers in a master slave or edge-triggered
configuration. This mode of operation occurs when WR
and LD are tied together. The asynchronous clear pin
resets the LTC1821 to zero scale and the LTC1821-1 to
midscale. CLR resets both the input and DAC registers.
These devices also have a power-on reset. Table 1 shows
the truth table for the LTC1821.
Unipolar Mode
(2-Quadrant Multiplying, VOUT = 0V to – VREF)
The LTC1821 can be used to provide 2-quadrant multiplying operation as shown in Figure 1. With a fixed – 10V
reference, the circuit shown gives a precision unipolar 0V
to 10V output swing.
5V
22pF
0.1µF
VREF
9
10
R1
8
REF
RCOM
11
ROFS
2
VCC
12
14
RFB
IOUT
V+
R1
16
DATA
INPUTS
ROFS
R2
RFB
15V
0.1µF
–
13
16-BIT DAC
VOUT
+
LTC1821
V – 20
25 TO 36,
3 TO 6
WR
WR
LD
CLR
15
24
LD
23
CLR
DNC* DNC* DNC*
18
7
19
NC
21
22
DGND
1
16
*DO NOT CONNECT
Unipolar Binary Code Table
DIGITAL INPUT
BINARY NUMBER
IN DAC REGISTER
ANALOG OUTPUT
VOUT
LSB
MSB
1111
1000
0000
0000
1111
0000
0000
0000
1111
0000
0000
0000
1111
0000
0001
0000
–VREF (65,535/65,536)
–VREF (32,768/65,536) = –VREF/ 2
–VREF (1/65,536)
0V
1821 F01
Figure 1. Unipolar Operation (2-Quadrant Multiplication) VOUT = 0V to – VREF
10
–15V
0.1µF
AGNDF AGNDS
17
VOUT =
0V TO
–VREF
LTC1821
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APPLICATIONS INFORMATION
Bipolar Mode
(4-Quadrant Multiplying, VOUT = – VREF to VREF)
operation can be achieved with a minimum of external
components—a capacitor and a single op amp, as shown
in Figure 2. With a fixed 10V reference, the circuit shown
gives a precision bipolar – 10V to 10V output swing.
The LTC1821 contains on chip all the 4-quadrant resistors
necessary for bipolar operation. 4-quadrant multiplying
VREF
3
2
+
–
5V
LT1001
0.1µF
22pF
9
10
R1
6
8
REF
RCOM
2
VCC
11
ROFS
12
14
RFB
IOUT
V+
R1
ROFS
R2
16
DATA
INPUTS
RFB
15V
0.1µF
–
13
16-BIT DAC
VOUT
+
LTC1821
V – 20
25 TO 36,
3 TO 6
WR
WR
LD
CLR
15
24
LD
23
DGND
CLR DNC* DNC* DNC* NC
7
18
19
21
22
1
AGNDF AGNDS
17
VOUT =
–VREF
TO VREF
–15V
0.1µF
16
*DO NOT CONNECT
Bipolar Offset Binary Code Table
DIGITAL INPUT
BINARY NUMBER
IN DAC REGISTER
LSB
MSB
1111
1000
1000
0111
0000
ANALOG OUTPUT
VOUT
1111
0000
0000
1111
0000
1111
0000
0000
1111
0000
1111
0001
0000
1111
0000
VREF (32,767/32,768)
VREF (1/32,768)
0V
–VREF (1/32,768)
–VREF
1821 F02
Figure 2. Bipolar Operation (4-Quadrant Multiplication) VOUT = – VREF to VREF
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LTC1821
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APPLICATIONS INFORMATION
Precision Voltage Reference Considerations
Because of the extremely high accuracy of the 16-bit
LTC1821, careful thought should be given to the selection
of a precision voltage reference. As shown in the section
describing the basic operation of the LTC1821, the output
voltage of the DAC circuit is directly affected by the voltage
reference; thus, any voltage reference error will appear as
a DAC output voltage error.
There are three primary error sources to consider when
selecting a precision voltage reference for 16-bit applications: output voltage initial tolerance, output voltage temperature coefficient (TC), and output voltage noise.
Initial reference output voltage tolerance, if uncorrected,
generates a full-scale error term. Choosing a reference
with low output voltage initial tolerance, like the LT1236
(±0.05%), minimizes the gain error due to the reference;
however, a calibration sequence that corrects for system
zero- and full-scale error is always recommended.
A reference’s output voltage temperature coefficient affects not only the full-scale error, but can also affect the
circuit’s INL and DNL performance. If a reference is
chosen with a loose output voltage temperature coefficient, then the DAC output voltage along its transfer
characteristic will be very dependent on ambient conditions. Minimizing the error due to reference temperature
coefficient can be achieved by choosing a precision reference with a low output voltage temperature coefficient
and/or tightly controlling the ambient temperature of the
circuit to minimize temperature gradients.
As precision DAC applications move to 16-bit and higher
performance, reference output voltage noise may contribute a dominant share of the system’s noise floor. This in
turn can degrade system dynamic range and signal-tonoise ratio. Care should be exercised in selecting a voltage
12
reference with as low an output noise voltage as practical
for the system resolution desired. Precision voltage references, like the LT1236, produce low output noise in the
0.1Hz to 10Hz region, well below the 16-bit LSB level in 5V
or 10V full-scale systems. However, as the circuit bandwidths increase, filtering the output of the reference may
be required to minimize output noise.
Grounding
As with any high resolution converter, clean grounding is
important. A low impedance analog ground plane and star
grounding should be used. AGNDF and AGNDS must be
tied to the star ground with as low a resistance as possible.
When it is not possible to locate star ground close to
AGNDF and AGNDS, separate traces should be used to
route these pins to the star ground. This minimizes the
voltage drop from these pins to ground due to the code
dependent current flowing into the ground plane. If the
resistance of these separate circuit board traces exceeds
1Ω, the circuit of Figure␣ 3 eliminates this code dependent
voltage drop error for high resistance traces.
To calculate PC track resistance in squares, divide the
length of the PC track by the width and multiply this result
by the sheet resistance of copper foil. For 1 oz copper
(≈ 1.4 mils thick), the sheet resistance is 0.045Ω per
square.
Table 2. Partial List of LTC Precision References Recommended
for Use with the LTC1821, with Relevant Specifications
INITIAL
TOLERANCE
TEMPERATURE
DRIFT
0.1Hz to 10Hz
NOISE
LT1019A-5,
LT1019A-10
±0.05%
5ppm/°C
12µVP-P
LT1236A-5,
LT1236A-10
±0.05%
5ppm/°C
3µVP-P
LT1460A-5,
LT1460A-10
±0.075%
10ppm/°C
20µVP-P
LT1790A-2.5
±0.05%
10ppm/°C
12µVP-P
REFERENCE
LTC1821
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APPLICATIONS INFORMATION
5V
LT1236A-10
9
10
R1
8
REF
RCOM
2
VCC
11
12
14
ROFS
RFB
IOUT
V + 15
R1
16
DATA
INPUTS
ROFS
R2
LTC1821
RFB
–
13
16-BIT DAC
VOUT
+
25 TO 36,
3 TO 6
V – 20
AGNDS
LD
WR
24
23
CLR DNC* DNC* DNC*
7
18
19
NC
22
21
DGND
19
VOUT =
0V TO –10V
–15V
16
0.1µF
AGNDF
17
*DO NOT CONNECT
6
2
LT1001
ERA82.004
3
ALTERNATE AMPLIFIER FOR OPTIMUM SETTLING TIME PERFORMANCE
AGNDS
AGNDF
16
200Ω
17
–
6
ERA82.004
2
200Ω
1000pF
LT1468
+
WR
LD
CLR
15V
0.1µF
+
4
22pF
0.1µF
6 10V
–
15V
2
3
1821 F03
Figure 3. Driving AGNDF and AGNDS with a Force/Sense Amplifier
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LTC1821
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TYPICAL APPLICATION
17-Bit Sign Magnitude Output Voltage DAC with Bipolar Zero Error of 140µV (0.92LSB at 17 Bits)
16
15
14
LTC203AC
15V
2
1
2
3
0.1µF
LT1236A-10
4
V+
6
3
2
+
–
5V
6
LT1468
0.1µF
0.1µF
V–
15pF
SIGN
BIT
10
9
R1
RCOM
22pF
8
REF
2 11
VCC ROFS
12
14
RFB
IOUT
V+
R1
ROFS
R2
16
DATA
INPUTS
RFB
13
+
WR
14
24
LD
23
CLR DNC* DNC* DNC* NC
7
18
19
21
22
DGND
1
AGNDF
AGNDS
17
16
VOUT
VOUT
V–
25 TO 36,
3 TO 6
WR
LD
CLR
15V
0.1µF
–
16-BIT DAC
LTC1821
15
20
–15V
0.1µF
*DO NOT CONNECT
1821 TA03
LTC1821
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
GW Package
36-Lead Plastic SSOP (Wide 0.300)
(LTC DWG # 05-08-1642)
15.290 – 15.544*
(0.602 – 0.612)
36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
10.160 – 10.414
(0.400 – 0.410)
7.417 – 7.595**
(0.292 – 0.299)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
2.286 – 2.387
(0.090 – 0.094)
2.463 – 2.641
(0.097 – 0.104)
0.254 – 0.406 × 45°
(0.010 – 0.016)
0° – 8° TYP
0.231 – 0.3175
(0.0091 – 0.0125)
0.610 – 1.016
(0.024 – 0.040)
NOTE: DIMENSIONS ARE IN MILLIMETERS
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.152mm (0.006") PER SIDE
0.800
(0.0315)
BSC
0.304 – 0.431
(0.012 – 0.017)
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.254mm (0.010") PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
0.127 – 0.305
(0.005 – 0.0115)
GW36 SSOP 1098
15
LTC1821
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
ADCs
Low Power 400ksps, 14-Bit ADC
20mW, Single or ±5V, Serial I/O
DACs
Op Amps
LTC1417
LTC1418
14-Bit, 200ksps, Single 5V ADC
15mW, Serial/Parallel ±10V
LTC1604/LTC1608
16-Bit, 333ksps/500ksps, ±5V ADC
90dB SINAD, 100dB THD, ±2.5V Inputs
LTC1605/LTC1606
16-Bit, 100ksps/250ksps, Single 5V ADC
±10V Inputs, 55mW/75mW, Byte or Parallel I/O
LTC1609
16-Bit, 200ksps, Single 5V ADC
±10V Inputs, 65mW, Serial I/O
LTC2400
24-Bit, Micropower ∆Σ ADC in SO-8
0.3ppm Noise, 4ppm INL, 10ppm Total Unadjusted Error, 200µA
LTC2410
24-Bit, Fully Differential, No Latency ∆Σ ADC
0.16ppm Noise, 2ppm INL, 10ppm Total Unadjusted Error, 200µA
LTC1591/LTC1597
Parallel 14-/16-Bit Current Output DACs
On-Chip 4-Quadrant Resistors
LTC1595/LTC1596
Serial 16-Bit Current Output DACs in SO-8/S16
Low Glitch, ±1LSB Maximum INL, DNL
LTC1599
Parallel 2 Byte 16-Bit Current Output DAC
On-Chip 4-Quadrant Resistors
LTC1650
Serial 16-Bit ±5V Voltage Output DAC
Low Noise and Low Glitch Rail-to-Rail VOUT
LTC1654
Dual 14-Bit Rail-to-Rail VOUT DAC
Programmable Speed/Power, 3.5µs/750µA, 8µs/450µA
LTC1655/LTC1655L
Serial 5V/3V 16-Bit Voltage Output DAC in SO-8
Low Power, Deglitched, Rail-to-Rail VOUT
LTC1657/LTC1657L
Parallel 5V/3V 16-Bit Voltage Output DAC
Low Power, Deglitched, Rail-to-Rail VOUT
LTC1658
Serial 14-Bit Voltage Output DAC
Low Power, 8-Lead MSOP Rail-to-Rail VOUT
LT1001
Precision Operational Amplifier
Low Offset, Low Drift
LT1468
90MHz, 22V/µs, 16-Bit Accurate Op Amp
Precise, 1µs Settling to 0.0015%
Bandgap Reference
±0.05% Initial Tolerance, 5ppm/°C
LT1236
Precision Buried Zener Reference
±0.05% Initial Tolerance, Low Noise 3µVP-P
LT1460
Micropower Bandgap Reference
±0.075% Initial Tolerance, 10ppm/°C
LT1790
SOT-23 Micropower, Low Dropout Reference
±0.05% Initial Tolerance, 10ppm/°C
References LT1019
16
Linear Technology Corporation
1821f LT/TP 0401 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 2000