19-1428; Rev 0; 2/99
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
Features
The MAX5120/MAX5121 are low-power, 12-bit, voltageoutput digital-to-analog converters (DACs) with an internal precision bandgap reference and an output amplifier.
The MAX5120 operates on a +5V supply with an internal
amplifier reference of +2.5V and is capable of a +4.095V
full-scale output range. The MAX5121, operating on +3V,
delivers its +2.0475V full-scale output with an internal
precision reference of +1.25V. If necessary, the user can
override the internal, <10ppm/°C voltage reference with
an external reference. Both devices draw only 500µA of
supply current, which reduces to 3µA in power-down
mode. In addition, their power-up reset feature allows for
a user-selectable initial output state of either 0V or midscale and minimizes output voltage glitches during
power-up.
♦ Single-Supply Operation
+5V (MAX5120)
+3V (MAX5121)
The serial interface is compatible with SPI™, QSPI™
and MICROWIRE™, which makes the MAX5120/
MAX5121 suitable for cascading multiple devices. Each
DAC has a double-buffered input organized as an input
register followed by a DAC register. A 16-bit shift register loads data into the input register. The DAC register
may be updated independently or simultaneously with
the input register.
♦ SPI/QSPI/MICROWIRE-Compatible, 3-Wire Serial
Interface
Both devices are available in a 16-pin QSOP package
and are specified for the extended industrial (-40°C to
+85°C) temperature range. For pin-compatible 14-bit
upgrades, see the MAX5170/MAX5172 data sheet;
for pin-compatible 13-bit versions, see the MAX5130/
MAX5131 data sheet.
♦ Space-Saving 16-Pin QSOP Package
♦ Full-Scale Output Range
+4.095V (MAX5120)
+2.0475V (MAX5121)
♦ Built-In 10ppm/°C (max) Precision Bandgap
Reference
+2.5V (MAX5120)
+1.25V (MAX5121)
♦ Adjustable Output Offset
♦ Pin-Programmable Shutdown Mode and PowerUp Reset (0V or Midscale Output Voltage)
♦ Buffered Output Capable of Driving 5kΩ 100pF
or 4–20mA Loads
♦ Pin-Compatible 13-Bit Upgrades Available
(MAX5130/MAX5131)
♦ Pin-Compatible 14-Bit Upgrades Available
(MAX5170/MAX5172)
________________________Applications
Industrial Process Controls
Automatic Test Equipment (ATE)
Digital Offset and Gain Adjustment
Motion Control
µP-Controlled Systems
Pin Configuration
TOP VIEW
15 REFADJ
RSTVAL 3
CLR 5
PART
TEMP. RANGE
PINPACKAGE
INL
(LSB)
MAX5120AEEE
-40°C to +85°C
16 QSOP
±0.5
MAX5120BEEE
-40°C to +85°C
16 QSOP
±1
MAX5121AEEE
-40°C to +85°C
16 QSOP
±1
MAX5121BEEE
-40°C to +85°C
16 QSOP
±2
16 VDD
OS 1
OUT 2
PDL 4
Ordering Information
14 REF
MAX5120
MAX5121
13 AGND
12 PD
CS 6
11 UPO
DIN 7
10 DOUT
SCLK 8
9
QSOP
DGND
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX5120/MAX5121
General Description
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
ABSOLUTE MAXIMUM RATINGS
VDD to AGND, DGND ...............................................-0.3V to +6V
AGND to DGND.....................................................-0.3V to +0.3V
Digital Inputs to DGND.............................................-0.3V to +6V
Digital Outputs (DOUT, UPO) to DGND .....-0.3V to (VDD + 0.3V)
OUT to AGND.............................................-0.3V to (VDD + 0.3V)
OS to AGND ...................................(AGND - 4V) to (VDD + 0.3V)
REF, REFADJ to AGND ..............................-0.3V to (VDD + 0.3V)
Maximum Current into Any Pin............................................50mA
Continuous Power Dissipation (TA = +70°C)
QSOP (derate 8.00mW/°C above +70°C) .....................667mW
Operating Temperature Range ..........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS—MAX5120 (+5V)
(VDD = +5V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
STATIC PERFORMANCE
Resolution
N
12
Bits
MAX5120A
-0.5
0.5
MAX5120B
-1
1
1
LSB
Integral Nonlinearity (Note 1)
INL
Differential Nonlinearity
DNL
-1
Offset Error (Note 2)
VOS
-10
10
mV
Gain Error
GE
-3
-0.2
3
mV
Full-Scale Voltage
VFS
4.0458
4.095
4.1442
V
Code = FFF hex, TA = +25°C
MAX5120A
3
10
MAX5120B
10
30
PSRR
4.5V ≤ VDD ≤ 5.5V
20
250
VREF
TA = +25°C
2.5
MAX5120A
3
MAX5120B
10
0 ≤ IOUT ≤ 100µA (sourcing)
0.1
Full-Scale Temperature
Coefficient (Note 3)
TCVFS
Power-Supply Rejection Ratio
LSB
ppm/°C
µV/V
REFERENCE
Output Voltage
Output Voltage Temperature
Coefficient
Reference External Load Regulation
TCVREF
VOUT/IOUT
Reference Short-Circuit Current
V
ppm/°C
1
4
REFADJ Current
REFADJ = VDD
3.3
µV/µA
mA
7
µA
DIGITAL INPUT
Input High Voltage
Input Low Voltage
Input Hysteresis
VIH
3
V
VIL
0.8
VHYS
Input Leakage Current
IIN
Input Capacitance
CIN
200
VIN = 0 or VDD
-1
0.001
V
mV
1
8
µA
pF
DIGITAL OUTPUTS
Output High Voltage
VOH
ISOURCE = 2mA
Output Low Voltage
VOL
ISINK = 2mA
2
VDD - 0.5
V
0.13
_______________________________________________________________________________________
0.4
V
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
(VDD = +5V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC PERFORMANCE
Voltage Output Slew Rate
SR
Output Settling Time
To ±0.5LSB, VSTEP = 4V
Output Voltage Swing (Note 4)
OS Input Resistance
ROS
83
Time Required to Exit Shutdown
CS = VDD, fSCLK = 100kHz,
VSCLK = 5Vp-p
Digital Feedthrough
0.6
V/µs
20
µs
0 to VDD
V
121
kΩ
2
ms
5
nV-s
POWER REQUIREMENTS
Power-Supply Voltage (Note 5)
Power-Supply Current (Note 5)
Power-Supply Current in Shutdown
VDD
4.5
5.5
V
IDD
500
600
µA
ISHDN
3
20
µA
ELECTRICAL CHARACTERISTICS—MAX5121 (+3V)
(VDD = +3V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
STATIC PERFORMANCE
Resolution
N
12
Bits
MAX5121A
-1
1
MAX5121B
-2
2
Integral Nonlinearity (Note 1)
INL
Differential Nonlinearity
DNL
-1
1
LSB
Offset Error (Note 2)
VOS
-10
10
mV
Gain Error
GE
-5
-0.2
5
mV
Full-Scale Voltage
VFS
2.0229
2.0475
2.0721
V
Data = FFF hex, TA = +25°C
MAX5121A
3
10
MAX5121B
10
30
PSRR
2.7V ≤ VDD ≤ 3.3V
20
250
VREF
TA = +25°C
1.25
MAX5121A
3
MAX5121B
10
0 ≤ IOUT ≤ 100µA (sourcing)
0.1
Full-Scale Temperature
Coefficient (Note 3)
TCVFS
Power-Supply Rejection Ratio
LSB
ppm/°C
µV/V
REFERENCE
Output Voltage
Output Voltage Temperature
Coefficient
Reference External Load Regulation
TCVREF
VOUT/IOUT
Reference Short-Circuit Current
V
ppm/°C
1
4
REFADJ Current
REFADJ = VDD
3.3
µV/µA
mA
7
µA
DIGITAL INPUT
Input High Voltage
Input Low Voltage
Input Hysteresis
VIH
2.2
V
VIL
VHYS
0.8
200
V
mV
_______________________________________________________________________________________
3
MAX5120/MAX5121
ELECTRICAL CHARACTERISTICS—MAX5120 (+5V) (continued)
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
ELECTRICAL CHARACTERISTICS—MAX5121 (+3V) (continued)
(VDD = +3V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Input Leakage Current
IIN
Input Capacitance
CIN
CONDITIONS
VIN = 0 or VDD
MIN
TYP
MAX
UNITS
-1
0.001
1
µA
8
pF
DIGITAL OUTPUTS
Output High Voltage
VOH
ISOURCE = 2mA
Output Low Voltage
VOL
ISINK = 2mA
VDD - 0.5
V
0.13
0.4
V
DYNAMIC PERFORMANCE
Voltage Output Slew Rate
SR
Output Settling Time
To ±0.5LSB, VSTEP = 2V
Output Voltage Swing (Note 4)
OS Input Resistance
ROS
83
Time Required to Exit Shutdown
CS = VDD, fSCLK = 100kHz,
VSCLK = 3Vp-p
Digital Feedthrough
0.6
V/µs
20
µs
0 to VDD
V
121
kΩ
2
ms
5
nV-s
POWER REQUIREMENTS
Power-Supply Voltage (Note 5)
VDD
3.6
V
Power-Supply Current (Note 5)
IDD
500
600
µA
ISHDN
3
20
µA
Power-Supply Current in Shutdown
2.7
TIMING CHARACTERISTICS—MAX5120 (+5V)
(VDD = +5V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCLK Clock Period
tCP
100
ns
SCLK Pulse Width High
tCH
40
ns
SCLK Pulse Width Low
tCL
40
ns
CS Fall to SCLK Rise Setup Time
tCSS
40
ns
SCLK Rise to CS Rise Hold Time
tCSH
0
ns
SDI Setup Time
tDS
40
ns
SDI Hold Time
tDH
0
ns
SCLK Rise to DOUT Valid
Propagation Delay Time
tDO1
CLOAD = 200pF
80
ns
SCLK Fall to DOUT Valid
Propagation Delay Time
tDO2
CLOAD = 200pF
80
ns
SCLK Rise to CS Fall Delay Time
tCS0
10
ns
CS Rise to SCLK Rise Hold Time
tCS1
40
ns
CS Pulse Width High
tCSW
100
ns
4
_______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
(VDD = +3V ±10%, OS = AGND = DGND = 0V, 33nF capacitor at REFADJ, internal reference, RL = 5kΩ, CL = 100pF, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCLK Clock Period
tCP
150
ns
SCLK Pulse Width High
tCH
75
ns
SCLK Pulse Width Low
tCL
75
ns
CS Fall to SCLK Rise Setup Time
tCSS
60
ns
SCLK Rise to CS Rise Hold Time
tCSH
0
ns
SDI Setup Time
tDS
60
ns
SDI Hold Time
tDH
0
ns
SCLK Rise to DOUT Valid
Propagation Delay Time
tDO1
CLOAD = 200pF
200
ns
SCLK Fall to DOUT Valid
Propagation Delay Time
tDO2
CLOAD = 200pF
200
ns
SCLK Rise to CS Fall Delay Time
tCS0
10
ns
CS Rise to SCLK Rise Hold Time
tCS1
75
ns
CS Pulse Width High
tCSW
150
ns
Note 1: Accuracy is guaranteed as shown in the following table:
Accuracy Guaranteed
VDD
(V)
From Code:
To Code:
5
10
4095
3
20
4095
Note 2: Offset is measured at the code closest to 10mV.
Note 3: The temperature coefficient is determined by the “box” method in which the maximum ∆VOUT over the temperature range is
divided by ∆T.
Note 4: Accuracy is better than 1.0LSB for VOUT = 10mV to (VDD - 180mV). Guaranteed by PSR test on end points.
Note 5: RLOAD = ∞ and digital inputs are at either VDD or DGND.
Typical Operating Characteristics
(VDD = +5V (MAX5120), VDD = +3V (MAX5121), RL = 5kΩ, CL = 100pF, OS = AGND, TA = +25°C, unless otherwise noted.)
0.10
DNL (LSB)
0.05
0.15
0
0.05
0
-0.05
-0.05
-0.10
-0.10
-0.15
-0.15
-0.20
1000
2000
3000
DIGITAL INPUT CODE
4000
5000
2.505
2.500
2.495
2.490
-0.20
0
2.510
REFERENCE VOLTAGE (V)
0.10
MAX5120
REFERENCE VOLTAGE vs. TEMPERATURE
MAX5120/21 toc02
0.15
INL (LSB)
0.20
MAX5120/21 toc01
0.20
MAX5120
DIFFERENTIAL NONLINEARITY vs.
DIGITAL INPUT CODE
MAX5120/21 toc03
MAX5120
INTEGRAL NONLINEARITY vs.
DIGITAL INPUT CODE
0
1000
2000
3000
DIGITAL INPUT CODE
4000
5000
-60 -40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX5120/MAX5121
TIMING CHARACTERISTICS—MAX5121 (+3V)
Typical Operating Characteristics (continued)
(VDD = +5V (MAX5120), VDD = +3V (MAX5121), RL = 5kΩ, CL = 100pF, OS = AGND, TA = +25°C, unless otherwise noted.)
(CODE = AAA HEX)
350
(CODE = 000 HEX)
MAX5120/21 toc05
(CODE = AAA HEX)
400
350
(CODE = 000 HEX)
300
250
200
4.0
3.5
SHUTDOWN CURRENT (µA)
400
300
450
SUPPLY CURRENT (µA)
450
-40
-20
0
20
40
60
80
100
4.5
5.0
5.5
6.0
MAX5120
FULL-SCALE OUTPUT vs. TEMPERATURE
MAX5120
FULL-SCALE ERROR vs. RESISTIVE LOAD
4.097
4.096
4.095
4.094
0.50
0.25
FULL-SCALE ERROR (LSB)
RL = 5kΩ
CL = 100pF
MAX5120/21 toc07
SUPPLY VOLTAGE (V)
4.098
2.0
1.0
4.0
TEMPERATURE (°C)
4.099
2.5
1.5
250
-60
3.0
-60
-40
-20
0
20
0
40
60
80
100
TEMPERATURE (°C)
MAX5120
DYNAMIC RESPONSE RISE TIME
MAX5120/21-09
MAX5120/21 toc08
SUPPLY CURRENT (µA)
500
MAX5120/21 toc04
500
MAX5120
SHUTDOWN CURRENT vs. TEMPERATURE
MAX5120
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX5120/21 toc06
MAX5120
SUPPLY CURRENT vs. TEMPERATURE
FULL-SCALE OUTPUT (V)
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
CS
5V/div
-0.25
-0.50
OUT
1V/div
-0.75
-1.00
-1.25
4.093
-1.50
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
0.1
1
10
100
5µs/div
RL (kΩ)
MAX5120
DYNAMIC RESPONSE FALL TIME
MAX5120
DIGITAL FEEDTHROUGH (SCLK, OUT)
MAX5120/21-10
MAX5120
MAJOR CARRY TRANSITION
MAX5120/21-12
MAX5120/21-11
CS
5V/div
SCLK
2V/div
CS
2V/div
OUT
1mV/div
AC COUPLED
OUT
100mV/div
AC COUPLED
OUT
1V/div
5µs/div
6
2µs/div
5µs/div
_______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
MAX5121
DIFFERENTIAL NONLINEARITY
vs. DIGITAL INPUT CODE
0.15
DNL (LSB)
0
0.05
-0.05
-0.1
-0.15
-0.2
-0.25
-0.3
0
1000
2000
3000
4000
1.244
1000
2000
3000
4000
1.240
5000
-60
-40
-20
0
20
40
60
80
100
DIGITAL INPUT CODE
TEMPERATURE (°C)
MAX5121
SUPPLY CURRENT vs. TEMPERATURE
MAX5121
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX5121
SHUTDOWN CURRENT vs. TEMPERATURE
300
CODE = 000 HEX
250
200
375
150
CODE = AAA HEX
350
325
300
-60
-40
-20
0
20
40
60
80
100
0.6
0.4
0
250
100
0.8
0.2
CODE = 000 HEX
275
1.0
MAX5120/21 toc-18
MAX5120/21 toc-17
400
SUPPLY CURRENT (µA)
MAX5120/21 toc-16
CODE = AAA HEX
350
2.5
2.7
2.9
3.1
3.3
3.5
3.7
-60
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
MAX5121
FULL-SCALE OUTPUT vs. TEMPERATURE
MAX5121
FULL-SCALE OUTPUT vs. RESISTIVE LOAD
MAX5121
DYNAMIC RESPONSE RISE TIME
2.044
2.042
2.040
2.038
MAX5120/21 toc-20
RL = 5kΩ
CL = 100pF
100
MAX5120/21-21
0.50
0.25
FULL-SCALE ERROR (LSB)
MAX5120/21 toc-19
2.046
FULL-SCALE OUTPUT (V)
1.246
DIGITAL INPUT CODE
400
SUPPLY CURRENT (µA)
0
5000
1.248
1.242
SHUTDOWN CURRENT (µA)
INL (LSB)
0.1
1.250
MAX5120/21 toc-15
0.2
MAX5120/21 toc-14
0.25
MAX5120/21 toc-13
0.3
MAX5121
REFERENCE VOLTAGE vs. TEMPERATURE
REFERENCE VOLTAGE (V)
MAX5121
INTEGRAL NONLINEARITY
vs. DIGITAL INPUT CODE
CS
2V/div
0
-0.25
-0.50
OUT
500mV/div
-0.75
1.00
2.036
-60
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
100
MAX5120/MAX5121
Typical Operating Characteristics (continued)
(VDD = +5V (MAX5120), VDD = +3V (MAX5121), RL = 5kΩ, CL = 100pF, OS = AGND, TA = +25°C, unless otherwise noted.)
0.1
10
1
100
2µs/div
RL (kΩ)
_______________________________________________________________________________________
7
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
Typical Operating Characteristics (continued)
(VDD = +5V (MAX5120), VDD = +3V (MAX5121), RL = 5kΩ, CL = 100pF, OS = AGND, TA = +25°C, unless otherwise noted.)
MAX5121
MAJOR CARRY TRANSITION
MAX5121
DIGITAL FEEDTHROUGH (SCLK, OUT)
MAX5121
DYNAMIC RESPONSE FALL TIME
MAX5120/21-24
MAX5120/21-23
MAX5120/21-22
CS
2V/div
SCLK
2V/div
CS
2V/div
OUT
500mV/div
OUT
500µV/div
AC COUPLED
OUT
100mV/div
AC COUPLED
5µs/div
2µs/div
2µs/div
Pin Description
8
PIN
NAME
1
OS
FUNCTION
2
OUT
3
RSTVAL
Reset Value Input (Digital Input)
1: Tie to VDD to select midscale as the output reset value.
0: Tie to DGND to select 0V as the output reset value.
4
PDL
Power-Down Lockout (Digital Input)
1: Normal operation.
0: Disallows shutdown (device cannot be powered down).
5
CLR
Reset DAC Input (Digital Input). Clears the DAC to its predetermined (RSTVAL) output state. Clearing the
DAC will cause it to exit a software shutdown state.
Offset Adjust (Analog Input)
Analog Output Voltage. High impedance if part is in shutdown.
6
CS
Active-Low Chip-Select Input (Digital Input)
7
DIN
Serial Data Input. Data is clocked in on the rising edge of SCLK.
8
SCLK
Serial Clock Input
9
DGND
Digital Ground
10
DOUT
Serial Data Output
11
UPO
12
PD
13
AGND
14
REF
15
REFADJ
16
VDD
User-Programmable Output (Digital Output)
Power-Down Input (Digital Input). Pulling PD high when PDL = VDD places the IC into shutdown with a
maximum shutdown current of 20µA.
Analog Ground
Buffered Reference Output/Input. In internal reference mode, the reference buffer provides a +2.5V
(MAX5120) or +1.25V (MAX5121) nominal output, externally adjustable at REFADJ. In external reference
mode, disable the internal reference by pulling REFADJ to VDD and applying the external reference to REF.
Analog Reference Adjust Input. Bypass with a 33nF capacitor to AGND. Connect to VDD when using an
external reference.
Positive Power Supply. Bypass with a 0.1µF capacitor in parallel with a 4.7µF capacitor to AGND.
_______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
PDL
PD
MAX5120/MAX5121
CS
VDD AGND DGND
DIN SCLK
SR
CONTROL
16-BIT
SHIFT REGISTER
DOUT
LOGIC
OUTPUT
UPO
OS
R
RSTVAL
DECODE
CONTROL
CLR
12
0.6384R
MAX5120
MAX5121
INPUT
REGISTER
DAC
REGISTER
OUT
DAC
GAIN = 1.6384X
BANDGAP 1.25V
REFERENCE
( ) FOR MAX5121 ONLY
2X
(1X)
4k
2.5V, (1.25V)
REFERENCE
BUFFER
REFADJ
REF
Figure 1. Simplified Functional Diagram
_______________Detailed Description
OS
The MAX5120/MAX5121 12-bit, voltage-output DACs
are easily configured with a 3-wire serial interface. They
include a 16-bit data-in/data-out shift register and have
a double-buffered input consisting of an input register
and a DAC register. In addition, these devices employ
precision bandgap references and trimmed internal
resistors to produce a gain of 1.6384V/V, maximizing
the output voltage swing (Figure 1). The MAX5120/
MAX5121 output amplifier’s offset-adjust pin allows for
a DC shift in the DAC outputs. The full-scale output voltage is +4.095V for the MAX5120 and +2.0475V for the
MAX5121. These DACs are designed with an inverted
R-2R ladder network (Figure 2) that produces a weighted output voltage proportional to the digital input code.
REF*
Internal Reference
AGND
Both the MAX5120 and MAX5121 use an on-board precision bandgap reference to generate an output voltage of +2.5V (MAX5120) or +1.25V (MAX5121). With a
low temperature coefficient of only 10ppm/°C (max),
the REF pin can source up to 100µA and may become
unstable with capacitive loads exceeding 100pF.
REFADJ can be used for minor adjustments (1%) to the
reference voltage. Use the circuits shown in Figure 3a
R
0.6384R
R
2R
2R
D0
R
2R
D9
OUT
R
2R
D10
2R
D11
SHOWN FOR ALL 1s ON DAC
*INTERNAL 2.5V (MAX5120) AND 1.25V (MAX5121)
OR EXTERNAL REFERENCE.
Figure 2. Simplified Inverted R-2R DAC Structure
_______________________________________________________________________________________
9
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
(MAX5120) and Figure 3b (MAX5121) to achieve these
adjustments. Connect a 33nF capacitor from REFADJ
to AGND to establish low-noise operation of the DAC.
Larger capacitor values may be used, but will result in
increased start-up delay. The time constant (τ) for the
start-up delay is determined by the REFADJ input
impedance of 4kΩ and CREFADJ:
τ = 4kΩ · CREFADJ
External Reference
An external reference may be applied to the REF pin.
Disable the internal reference by pulling REFADJ to
VDD. This allows an external reference signal (AC- or
DC-based) to be fed into the REF pin. For proper operation, do not exceed the input voltage range limits of
0V to (VDD - 1.4V) for VREF.
Determine the output voltage using the following equation (REFADJ = VDD; OS = AGND):
VOUT = [VREF · (NB / 4096)] · 1.6384V/V
where NB is the numeric value of the MAX5120/
MAX5121 input code (0 to 4095), VREF is the external
reference voltage, and 1.6384V/V is the gain of the
internal output amplifier. The REF pin has a minimum
input resistance of 40kΩ and is code-dependent.
Output Amplifier
The output amplifier of the MAX5120/MAX5121
employs a trimmed resistor-divider to set a gain of
+1.6384V/V and minimize the gain error. With its onboard laser-trimmed +1.25V reference and the output
buffer gain, the MAX5121 achieves a full-scale output
of +2.0475V, while the MAX5120 provides a +4.095V
full-scale output with a +2.5V reference.
The output amplifier has a typical slew rate of 0.6V/µs
and settles to ±0.5LSB within 20µs, with a load of 5kΩ
in parallel with 100pF. Loads less than 1kΩ may result
in degraded performance.
The OS pin may be used to adjust the output offset voltage. For instance, to achieve a +1V offset, apply
-1.566V (Offset = -[Output Buffer Gain - 1] · VOS) to OS
to produce an output voltage range from +1V to (1V +
VREF · 1.6384V/V). Note that the DAC’s output range is
still limited by the maximum output voltage specification.
Power-Down Mode
The MAX5120/MAX5121 feature software- and hardware-programmable (PD pin) shutdown modes that
reduce the typical supply current to 3µA. To enter software shutdown mode, program the control sequence
for the DAC as shown in Table 1.
In shutdown mode, the amplifier output becomes high
impedance and the serial interface remains active.
Data in the input registers is saved, allowing the
MAX5120/MAX5121 to recall the output state prior to
entering shutdown when returning to normal operation
mode. To exit shutdown mode, load both input and
DAC registers simultaneously or update the DAC register from the input register. When returning from shutdown mode, wait 2ms for the reference to settle. When
using an external reference, the DAC requires only
20µs for the output to stabilize.
+5V
+3V
MAX5120
90k
400k
100k
400k
REFADJ
33nF
Figure 3a. MAX5120 Reference Adjust Circuit
10
MAX5121
15k
100k
REFADJ
33nF
Figure 3b. MAX5121 Reference Adjust Circuit
______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
MAX5120/MAX5121
Table 1. Serial-Interface Programming Commands
16-BIT SERIAL WORD
FUNCTION
C2
C1
C0
D11 ............... D0
S0*
0
0
0
XXXXXXXXXXXX
0
No operation.
0
0
1
12-Bit DAC Data
0
Load input register; DAC register unchanged.
0
1
0
12-Bit DAC Data
0
Simultaneously load input and DAC registers; exit shutdown.
0
1
1
XXXXXXXXXXXX
0
Update DAC register from input register; exit shutdown.
1
0
1
XXXXXXXXXXXX
0
Shutdown DAC (provided PDL = 1)
1
0
0
XXXXXXXXXXXX
0
UPO goes low (default).
1
1
0
XXXXXXXXXXXX
0
UPO goes high.
1
1
1
1XXXXXXXXXXX
0
Mode 1; DOUT clocked out on SCLK’s rising edge.
1
1
1
00XXXXXXXXXX
0
Mode 0; DOUT clocked out on SCLK’s falling edge (default).
X = Don’t care
* S0 is a sub-bit and is always zero.
Power-Down Lockout Input (PDL)
The power-down lockout pin (PDL) disables shutdown
when low. When in shutdown mode, a high-to-low transition on PDL will wake up the DAC with its output still
set to the state prior to power-down. PDL can also be
used to wake up the device asynchronously.
Power-Down Input (PD)
Pulling PD high places the MAX5120/MAX5121 in shutdown mode. Pulling PD low will not return the MAX5120/
MAX5121 to normal operation. A high-to-low transition
on PDL or appropriate commands (Table 1) via the serial interface are required to exit power-down.
VDD
SS
DIN
MAX5120
MAX5121 SCLK
CS
Serial-Interface Configuration
(SPI/QSPI/MICROWIRE/PIC16/PIC17)
The MAX5120/MAX5121 3-wire serial interface is compatible with SPI, QSPI, PIC16/PIC17 (Figure 4) and
MICROWIRE (Figure 5) interface standards. The 2-bytelong serial input word contains three control bits, 12 data
bits in MSB-first format and one sub-bit, which is always
zero (Table 2).
The MAX5120/MAX5121’s digital inputs are double
buffered, which allows the user to:
• Load the input register without updating the DAC
register;
• Update the DAC register with data from the input
register;
• Update the input and DAC registers concurrently.
MOSI
SCK
SPI/QSPI
PORT
(PIC16/PIC17)
I/O
CPOL = 0, CPHA = 0
CHE = 1, CKP = 0, SMP = 0,
SSPM3–SSPMO = 0001
( ): PIC16/PIC17 ONLY
Figure 4. SPI/QSPI Interface Connections (PIC16/PIC17)
SCLK
MAX5120
MAX5121
SK
MICROWIRE
PORT
DIN
SO
CS
I/O
Figure 5. MICROWIRE Interface Connections
______________________________________________________________________________________
11
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
PIC16 with SSP Module and
PIC17 Interface
The 16-bit input word may be sent in two 1-byte packets (SPI-, MICROWIRE- and PIC16/PIC17-compatible),
with CS low during this period. The control bits C2, C1,
and C0 (Table 1) determine:
• The clock edge on which DOUT is to be clocked out
via the serial interface;
• The state of the user-programmable logic output;
• The configuration of the device after shutdown.
The MAX5120/MAX5121 are compatible with a PIC16/
PIC17 controller (µC), using the synchronous serial port
(SSP) module. To establish SPI communication connect
the controller as shown in Figure 4 and configure the
PIC16/PIC17 as system master by initializing its synchronous serial port control register (SSPCON) and
synchronous serial port status register (SSPSTAT) to
the bit patterns shown in Tables 3 and 4.
In SPI mode, the PIC16/PIC17 µCs allow 8 bits of data
to be transmitted synchronously and received simultaneously. Two consecutive 8-bit writings (Figure 6) are
necessary to feed the DAC with three control bits and
12 data bits plus one sub-bit. DIN data transitions on
the serial clock’s falling edge and is clocked into the
DAC on SCLK’s rising edge. The first 8 bits on DIN contain the 3 control bits (C2, C1, and C0) and the first five
data bits (D11–D7). The second 8-bit word contains the
remaining bits (D6–D0), and the sub-bit S0.
The general timing diagram in Figure 6 illustrates how
data is acquired. CS must be low for the part to receive
data. With CS low, data at DIN is clocked into the register on the rising edge of SCLK. When CS transitions
high, data is latched into the input and/or DAC registers,
depending on the setting of the three control bits C2,
C1, and C0. The maximum serial clock frequency guaranteed for proper operation is 10MHz for the MAX5120
and 6.6MHz for the MAX5121. Figure 7 depicts a more
detailed timing diagram of the serial interface.
Table 2. Serial Data Format
MSB ............................................................................... LSB
⇐
⇒
16 BITS OF SERIAL DATA
Control Bits
MSB .... Data Bits ..... LSB
Sub-Bit
C2, C1, C0
D11................................D0
S0
CS
COMMAND
EXECUTED
SCLK
1
DIN
C2
8
C1
C0 D11 D10
D9
D8
9
D7
D6
16
D5
D4
D3
D2
D1
D0
S0
Figure 6. Serial-Interface Timing
tCSW
CS
tCS0
tCSH
tCSS
tCS1
SCLK
tCH
tCL
tCP
DIN
tDS
tDO1
tDO2
tDH
DOUT
Figure 7. Detailed Serial-Interface Timing
12
______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
CONTROL BIT
MAX5120/MAX5121
SETTINGS
SYNCHRONOUS SERIAL-PORT CONTROL REGISTER
(SSPCON)
WCOL
BIT7
X
Write Collision Detection Bit
SSPOV
BIT6
X
Receive Overflow Detection Bit
SSPEN
BIT5
1
Synchronous Serial Port Enable Bit.
0: Disables serial port and configures these pins as I/O port pins.
1: Enables serial port and configures SCK, SDO, and SCI as serialport pins.
Clock Polarity Select Bit. CKP = 0 for SPI master-mode selection.
CKP
BIT4
0
SSPM3
BIT3
0
SSPM2
BIT2
0
SSPM1
BIT1
0
SSPM0
BIT0
1
Synchronous Serial Port Mode Select Bit. Sets SPI master mode
and selects fCLK = fOSC / 16.
X = Don’t care
Table 4. Detailed SSPSTAT Register Contents
CONTROL BIT
MAX5120/MAX5121
SETTINGS
SYNCHRONOUS SERIAL-PORT CONTROL REGISTER
(SSPSTAT)
SMP
BIT7
0
SPI Data Input Sample Phase. Input data is sampled at the middle of the data output time.
CKE
BIT6
1
SPI Clock Edge Select Bit. Data will be transmitted on the rising
edge of the serial clock.
D/A
BIT5
X
Data Address Bit
P
BIT4
X
Stop Bit
S
BIT3
X
Start Bit
R/W
BIT2
X
Read/Write Bit Information
UA
BIT1
X
Update Address
BF
BIT0
X
Buffer Full Status Bit
X = Don’t care
Serial Data Output
User-Programmable Output (UPO)
The contents of the internal shift register are output
serially on DOUT, which allows for daisy-chaining (see
Applications Information) of multiple devices as well as
data readback. The MAX5120/MAX5121 may be programmed to shift data out on DOUT on the serial
clock’s rising edge (Mode 1) or falling edge (Mode 0).
The latter is the default during power-up and provides a
lag of 16 clock cycles, maintaining SPI, QSPI,
MICROWIRE, and PIC16/PIC17 compatibility. In Mode
1, the output data lags DIN by 15.5 clock cycles.
During power-down, DOUT retains its last digital state
prior to shutdown.
The UPO feature allows an external device to be controlled through the serial-interface setup (Table 1),
thereby reducing the number of microcontroller I/O
ports required. During power-down, this output will
retain the last digital state before shutdown. With CLR
pulled low, UPO will reset to the default state after wake
up.
______________________________________________________________________________________
13
MAX5120/MAX5121
Table 3. Detailed SSPCON Register Contents
__________Applications Information
Definitions
Integral Nonlinearity (INL)
Integral nonlinearity (Figure 8a) is the deviation of the
values on an actual transfer function from a straight
line. This straight line can be either a best-straight-line
fit (closest approximation to the actual transfer curve)
or a line drawn between the endpoints of the transfer
function, once offset and gain errors have been nullified. For a DAC, the deviations are measured at every
single step.
Differential Nonlinearity (DNL)
Differential nonlinearity (Figure 8b) is the difference
between an actual step height and the ideal value of
1LSB. If the magnitude of the DNL is less than 1LSB, the
DAC guarantees no missing codes and is monotonic.
Offset Error
The offset error (Figure 8c) is the difference between
the ideal and the actual offset point. For a DAC, the offset point is the step value when the digital input is zero.
This error affects all codes by the same amount and
can usually be compensated for by trimming.
Gain Error
Gain error (Figure 8d) is the difference between the
ideal and the actual full-scale output voltage on the
transfer curve, after nullifying the offset error. This error
alters the slope of the transfer function and corresponds to the same percentage error in each step.
6
6
ANALOG OUTPUT VALUE (LSB)
ANALOG OUTPUT VALUE (LSB)
7
5
4
AT STEP
011 (1/2 LSB )
3
2
AT STEP
001 (1/4 LSB )
1
1 LSB
5
DIFFERENTIAL LINEARITY
ERROR (-1/4 LSB)
4
3
1 LSB
2
DIFFERENTIAL
LINEARITY ERROR (+1/4 LSB)
1
0
0
000
001
010
011
100
101
110
000
111
001
IDEAL DIAGRAM
IDEAL OFFSET
POINT
0
000
001
OFFSET ERROR
(+1 1/4 LSB)
ANALOG OUTPUT VALUE (LSB)
2
ACTUAL
OFFSET
POINT
14
101
GAIN ERROR
(-1 1/4 LSB)
6
IDEAL DIAGRAM
ACTUAL
FULL-SCALE
OUTPUT
5
4
0
010
011
000 100
101
110
DIGITAL INPUT CODE
DIGITAL INPUT CODE
Figure 8c. Offset Error
100
IDEAL FULL-SCALE OUTPUT
7
ACTUAL
DIAGRAM
1
011
Figure 8b. Differential Nonlinearity
Figure 8a. Integral Nonlinearity
3
010
DIGITAL INPUT CODE
DIGITAL INPUT CODE
ANALOG OUTPUT VALUE (LSB)
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
Figure 8d. Gain Error
______________________________________________________________________________________
111
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
+5V/+3V
REF
OS
VDD
Digital Feedthrough
Digital feedthrough is noise generated on the DAC’s
output when any digital input transitions. Proper board
layout and grounding will significantly reduce this
noise, but there will always be some feedthrough
caused by the DAC itself.
0.6384R
DAC
OUT
AGND
Unipolar Output
Figure 9 shows the MAX5120/MAX5121 setup for
unipolar, Rail-to-Rail ® operation with a gain of
1.6384V/V. With its +2.5V internal reference, the
MAX5120 can generate a unipolar output range of 0V
to +4.095V. The MAX5121 produces a range of 0V to
+2.0475V with its on-board +1.25V reference. Table 5
lists example codes for unipolar output voltages. An offset to the output voltage can be achieved by simply
connecting the appropriate voltage to the OS pin, as
shown in Figure 10.
Figure 9. Unipolar Output Circuit (OS = AGND) Using Internal
(1.25V/2.5V) or External Reference. With external reference,
pull REFADJ to VDD.
+5V/+3V
REF
VOS
R
MAX5120
MAX5121
0.6384R
DAC
OUT
AGND
DGND
Figure 10. Circuit for Adding Offset to the DAC’s Output
+5V/+3V
50k
REF
Reset (RSTVAL) and Clear (CLR) Functions
The CLR pin has a minimum input resistance of 40kΩ in
series with a diode to the supply voltage (VDD). If the
digital voltage is higher than the supply voltage for the
part, a small input current may flow, but this current will
be limited to (V CLR - VDD - 0.5V) / 40kΩ.
Note: Clearing the DAC will also cause the part to exit
software shutdown (PD = 0).
OS
REFADJ
VDD
Bipolar Output
The MAX5120/MAX5121 DACs offer a clear pin (CLR)
that resets the output to a certain value, depending
upon how RSTVAL is set. RSTVAL = DGND sets the
output to 0, and RSTVAL = VDD sets the output to midscale when CLR is pulled low.
DGND
GAIN = 1.638V/V
The MAX5120/MAX5121 can be configured for unitygain bipolar operation (OS = OUT) using the circuit
shown in Figure 11. The output voltage VOUT is thereby
given by the following equation:
VOUT = VREF · [ {G · (NB / 4096)} - 1]
where NB is the numeric value of the DAC’s binary
input code, VREF is the voltage of the internal (or external) precision reference, and G is the overall gain. The
application circuit in Figure 11 uses a low-cost operational amplifier (MAX4162) external to the MAX5120/
MAX5121 in a unity-gain configuration. This provides
an overall circuit gain of 2V/V. Table 6 lists example
codes for bipolar output voltages.
R
MAX5120
MAX5121
50k
OS
VDD
R
MAX5120
MAX5121
V+
0.6384R
VOUT
DAC
OUT
DGND
AGND
MAX4162
V-
Figure 11. Unity-Gain Bipolar Output Circuit Using Internal
(+1.25V/+2.5V) or External Reference. With external reference,
pull REFADJ to VDD.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
______________________________________________________________________________________
15
MAX5120/MAX5121
Settling Time
The settling time is the amount of time required from the
start of a transition until the DAC output settles to its new
output value within the converter’s specified accuracy.
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
Table 5. Unipolar Code Table (Gain = 1.6384V/V)
DAC CONTENTS
ANALOG OUTPUT
INTERNAL REFERENCE
SUB-BIT
S0
MAX5120
MAX5121
1111 1111 1111
0
+4.0950V
+2.0475V
+VREF (4095 / 4096) · 1.6384
1000 0000 0001
0
+2.049V
+1.0245V
+VREF (2049 / 4096) · 1.6384
1000 0000 0000
0
+2.048V
+1.024V
+VREF (2048 / 4096) · 1.6384
0111 1111 1111
0
+2.047V
+1.0235V
+VREF (2047 / 4096) · 1.6384
0000 0000 0001
0
+1mV
+0.5mV
0000 0000 0000
0
0V
0V
+VREF (1 / 4096) · 1.6384
0V
MSB
LSB
EXTERNAL REFERENCE
Table 6. Bipolar Code Table for Figure 11
DAC CONTENTS
MSB
ANALOG OUTPUT
SUB-BIT
SO
LSB
INTERNAL REFERENCE
MAX5120
MAX5121
EXTERNAL REFERENCE
1111 1111 1111
0
+2.49878V
+1.24939V
VREF · [ {2 · (4095 / 4096)} - 1]
1000 0000 0001
0
+1.2207mV
+610.35µV
VREF · [ {2 · (2049 / 4096)} - 1]
1000 0000 0000
0
0V
0V
VREF · [ {2 · (2048 / 4096)} - 1]
0111 1111 1111
0
-1.2207µV
-610.35µV
VREF · [ {2 · (2047 / 4096)} - 1]
0000 0000 0001
0
-2.49878V
-1.24939V
VREF · [ {2 · (14096)} - 1]
0000 0000 0000
0
-2.5V
-1.25V
-VREF
SCLK
DIN
CS
SCLK
SCLK
I
II
III
MAX5120
MAX5121
MAX5120
MAX5121
MAX5120
MAX5121
DOUT
DIN
DOUT
DIN
CS
DOUT
CS
TO OTHER
SERIAL DEVICES
Figure 12. Daisy-Chaining Multiple Devices with the Digital I/Os DIN/DOUT
Daisy-Chaining Devices
Any number of MAX5120/MAX5121s can be daisychained simply by connecting the serial data output pin
(DOUT) of one device to the digital input pin (DIN) of
the following device in the chain (Figure 12).
16
Another configuration allows several MAX5120/
MAX5121 DACs to share one common DIN signal line
(Figure 13). In this configuration, the data bus is common to all devices; data is not shifted through a daisychain. However, more I/O lines are required in this
configuration, because each IC needs a dedicated CS
line.
______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
= VDD). Bypass the power supply with a 4.7µF capacitor in parallel with a 0.1µF capacitor to AGND. Minimize
lead lengths to reduce lead inductance.
The MAX5120/MAX5121 have multiplying capabilities
within the reference input voltage range specifications.
Figure 14 shows a technique for applying a sinusoidal
input to REF, where the AC signal is offset before being
applied to the reference input.
Layout Considerations
Digital and AC transient signals coupling to AGND can
create noise at the output. Connect AGND to the highest quality ground available. Use proper grounding
techniques, such as a multilayer board with a lowinductance ground plane. Wire-wrapped boards and
sockets are not recommended. If noise becomes an
issue, shielding may be required.
Power-Supply and Bypassing
Considerations
On power-up, the input and DAC registers are cleared
to either zero (RSTVAL = DGND) or midscale (RSTVAL
DIN
SCLK
CS1
CS2
TO OTHER
SERIAL DEVICES
CS3
I
CS
II
CS
MAX5120
MAX5121
III
CS
MAX5120
MAX5121
MAX5120
MAX5121
SCLK
SCLK
SCLK
DIN
DIN
DIN
Figure 13. Multiple Devices Share One Common Digital Input (DIN)
+5V/+3V
+5V/+3V
AC
REFERENCE
INPUT
26k
MAX495
500mVp-p
10k
REF
VDD
R
OS
0.6384R
DAC
AGND
OUT
MAX5120
MAX5121
DGND
Figure 14. External Reference with AC Components
______________________________________________________________________________________
17
MAX5120/MAX5121
Using an External Reference
with AC Components
___________________Chip Information
TRANSISTOR COUNT: 3308
SUBSTRATE CONNECTED TO AGND.
Package Information
QSOP.EPS
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
18
______________________________________________________________________________________
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
______________________________________________________________________________________
MAX5120/MAX5121
NOTES
19
MAX5120/MAX5121
+3V/+5V, 12-Bit, Serial Voltage-Output DACs
with Internal Reference
NOTES
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.