EVALUATION KIT AVAILABLE
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
General Description
The MAX12900 is an ultra-low-power, highly integrated
4-20mA sensor transmitter. The MAX12900 integrates
ten building blocks in a small package: a wide input supply
voltage LDO, two conditioner circuits for pulse-widthmodulated (PWM) inputs, two low-power, low-drift, generalpurpose operational amplifiers (op amp) one wide bandwidth,
zero-offset drift operational amplifier; two diagnostic
comparators, a power-up sequencer with power good
output to allow for a smooth power-up, and a low-drift
voltage reference.
The MAX12900 converts PWM data from a microcontroller
into current over a 4-20mA loop with two, three, or fourwire configurations.
The equivalent to an ultra-low-power, high-resolution,
digital-to-analog converter is realized with the combination
of two-PWM signals received from a microcontroller, the
two conditioner circuits, and an active filter built with the
integrated low-power op amp. The outputs of the two
conditioner circuits provide a stable PWM amplitude over
voltage supply and temperature variation. The wide bandwidth amplifier, in combination with a discrete transistor,
converts a voltage input into a current output and allows
HART and Foundation Fieldbus H1 signal modulation.
The zero-offset operational amplifier and the low-drift
voltage reference provide negligible error over wide
temperature. The low-power operational amplifier and
comparators provide building blocks for enhanced
diagnostic features. Supply rail monitoring, output
current readback, open circuit and failure detection are a
few examples of diagnostic features. All these features,
as well as ultra-low-power and high accuracy make the
MAX12900 ideal for loop-powered smart sensor transmitters
for industrial application.
The MAX12900 is available in 5mm x 5mm 32-pin TQFN
package and operates over a wide industrial temperature
range of -40°C to +125°C.
19-100086; Rev 2; 3/18
Benefits and Features
●● Wide Input Supply Range: 4.0V to 36V
●● Ultra-Low-Power Consumption: 170µA (typ)
●● High Linearity: 0.01% (Max Error)
●● High Resolution: Up to 16 Bit
●● Low Drift Voltage Reference: 10ppm/°C max
●● Wide Temperature Range: -40°C to +125°C
●● Small Package: 5mm x 5mm x 0.8mm 32-pin TQFN
Applications
●●
●●
●●
●●
Loop-Powered 4-20mA Current Transmitter
Smart Sensors
Remote Instrumentation
Industrial Automation and Process Control
Ordering Information appears at end of data sheet.
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Functional Block Diagram
VCCI
VCC
1.2V
VREF
LDOFB
VCCI
VCCID PWRGOOD
VDD
POWER-UP
SEQUENCER
LDO
VDD
VCCI
COMP2N
MAX12900
COMP2O
COMP2P
VDD
VCCI
COMP1N
COMP1O
COMP1P
COMPARATORS
VCCI
OP1N
OP1O
OP1
OP1P
VCCI
OP2N
OP2O
OP2
OP2P
VCCI
OP3N
OP3O
OP3
OP3P
OP-AMPS
VCCI
VCCI
REFGND
MAX12900 INTEGRATES 10 BUILDING BLOCKS:
LDO
POWER-UP SEQUENCER
TWO COMPARATORS (COMP1, COMP2)
TWO GENERAL PURPOSE OP AMPS (OP1, OP2)
ONE LOW DRIFT OP AMP (OP3)
2.5V PRECISION REFERENCE
TWO PWM RECEIVERS (PWMA, PWMB)
REFO
VREF
REFBUF
2.5V
VREF
VCCI
1V
PWMAO
PWMAP
SHDN
VCCI
REFBUF
1V
PWMBO
PWMBP
SHDN
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PWM
EP
Maxim Integrated │ 2
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Absolute Maximum Ratings
VCC to GND...........................................................-0.3V to +40V
VCC to VCCI..........................................................-0.3V to +40V
VCCI and VCCID to GND........................................-0.3V to +6V
VCCI to VCCID......................................................-0.3V to +0.3V
VDD to GND.............................................................-0.3V to +6V
PWRGOOD to GND................................... -0.3V to VCCI + 0.3V
LDOFB to GND.......................................... -0.3V to VCCI + 0.3V
I/C and REFGND to GND....................................-0.3V to + 0.3V
SHDN to GND............................................ -0.3V to VCCI + 0.3V
REFO to GND............................................ -0.3V to VCCI + 0.3V
Op Amps
OP1O, OP2O, OP3O to GND.................... -0.3V to VCCI + 0.3V
OP1P, OP1N, OP2P, OP2N, OP3P,
OP3N to GND.......................-0.3V to min [4.5V, VCCI + 0.3V]
Current into OP1P, OP1N, OP2P, OP2N,
OP3P, OP3N..................................................................±20mA
Current into OP3O............................................................±30mA
Output Short-Circuit Duration for OP1 and
OP2 to VCCI or GND.............................................Continuous
Comparators
COMP1P, COMP1N, COMP2P, COMP2N
to GND.................................................... -0.3V to VCCI + 0.3V
COMP1O, COMP2O to GND...................... -0.3V to VDD + 0.3V
Current into COMP1P, COMP1N,
COMP2P, COMP2N......................................................±20mA
Output Short-Circuit Duration to
VDD or GND...........................................................Continuous
PWM Conditioners
PWMAP, PWMBP to GND.......................... -0.3V to VCCI + 0.3V
PWMAO, PWMBO to GND........................ -0.3V to VCCI + 0.3V
Current into PWMAP, PWMBP..........................................±20mA
Output Short-Circuit Duration to VCCI or GND..........Continuous
Continuous Power Dissipation (TA = +70°C,
derate 35.7mW/°C above +70°C)............................2857.1mW
Operating Temperature Range.......................... -40°C to +125°C
Functional Temperature Range
(Startup condition)......................................... -55°C to +125°C
Maximum Junction Temperature......................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Soldering Temperature (reflow)........................................+260°C
Lead Temperature............................................................+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.
Package Information
32 TQFN
PACKAGE CODE
T3255
Outline Number
21-0140
Land Pattern Number
90-0015
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
40.2°C/W
Junction to Case (θJC)
2.0°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
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Maxim Integrated │ 3
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics
Voltage Reference
VCCI = +3.0V to +5.5V, VGND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C, VCCI = +3.3V.
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
140
µV/V
VOLTAGE REFERENCE 2.5V
STATIC
Supply Voltage
VCCI
Guaranteed by line regulation test
3.0
VCCI Line Regulation
∆VREF/
∆VCCI
3.0V ≤ VCCI ≤ 5.5V
20
VCC Line Regulation
∆VREF/
∆VCC
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V
1.2
Output Voltage
VOUT
TA = +25°C
2.495
2.500
2.505
V
2
10
ppm/°C
Output Voltage
Temperature Coefficient
TCVOUT
CREF = 2nF (Note 2)
Temperature Hysteresis
∆VREF/
Cycle
CREF = 2nF
-140
Load Regulation
∆VREF/
∆IOUT
Sourcing 0V ≤ IOUT ≤ 500 µA
0.14
Short-Circuit Current
ISC
Maximum Capacitive
Load
CREF
Short to GND
nV/V
ppm
0.6
µV/µA
3
mA
2
nF
DYNAMIC
VCCI Ripple Rejection
VREF/
VCCI
VCCI = 3.3V, f = 120Hz
90
dB
VCC Ripple Rejection
VREF/
VCC
VCC = 12V, VCCI = 3.3V, f = 120Hz
160
dB
Turn-On Settling Time
tR
From 90% of VCCI to within 0.1% of VREF,
CREF = 2nF
85
µs
0.1Hz to 10Hz
40
µVp-p
10Hz to 10kHz
125
µVRMS
Noise Voltage
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eREF
Maxim Integrated │ 4
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
PWM Conditioners
VCCI = +3.0V to +5.5V, VGND = 0V, outputs connected to 100kΩ in parallel with 10pF terminated to VREF/2, input pulses have 10ns
rise and fall times, PWM period = 100µs, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C, VCCI = +3.3V.
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
PWMA, PWMB
STATIC
Supply Voltage
VCCI Supply Rejection
Ratio of Input Threshold
Voltage
VCCI
PSRRVTH
VCC Supply Rejection
Ratio of Input Threshold
Voltage
VCCI Supply Rejection
Ratio of Output Voltage
High
PSRRVOH
VCC Supply Rejection
Ratio of Output Voltage
High
Guaranteed by PSRRVOH test
3.0
3.0V ≤ VCCI ≤ 5.5V
65
dB
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V
150
dB
75
dB
160
dB
3.0V ≤ VCCI ≤ 5.5V, no load
59
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V, no load
Input Voltage Range
0
Input Voltage High
VIH
PWMAP, PWMBP, SHDN
Input Voltage Low
VIL
PWMAP, PWMBP, SHDN
PWMAP, PWMBP Input
Threshold
VTH
VCCI
1.4
V
0.6
PWMAP, PWMBP Input
Threshold Accuracy
V
V
1.0
V
1
mV
PWMAP, PWMBP
Hysteresis
PWMHYS
5
mV
SHDN Hysteresis
SHDNHYS
50
mV
-1
nA
2
pF
Input Bias Current
IB
Input Capacitance
CIN
Output Voltage High
VOH
VREF - VOUT, ISOURCE = 100 µA
Output Voltage Low
VOL
VOUT – VGND, ISINK = 100 µA
Short Circuit Current
ISC
VPWMAP = VPWMBP = 0V
0.1
0.1
V
V
PWMAO or PWMBO short to VREF
-12
mA
PWMAO or PWMBO short to GND
6
mA
Output High Level
Voltage Matching
Difference between the voltage of the two
PWM outputs
-2
+2
mV
Output Low Level
Voltage Matching
Difference between the voltage of the two
PWM outputs
-2
+2
mV
PWMAO, PWMBO
Output Voltage High
Drift
Linearity
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7
From code 10 to code 245 (Note 2), Figure 1
µV/°C
0.01
%FSR
Maxim Integrated │ 5
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
PWM Conditioners (continued)
VCCI = +3.0V to +5.5V, VGND = 0V, outputs connected to 100kΩ in parallel with 10pF terminated to VREF/2, input pulses have 10ns
rise and fall times, PWM period = 100µs, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C, VCCI = +3.3V.
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC
Propagation Delay
Active to Shut down
tSHDN
From 50% of SHDN to when PWM outputs
are Hi-Z
10
µs
Propagation Delay Shut
down to Active
tACT
From 50% of SHDN to when PWM outputs
are active
10
µs
Minimum Input Pulse
Width
IPW
Single high state, guaranteed by PWM
timing tests
Driver Rise Time for
PWMAO and PWMBO
RTA, RTB
Driver Fall Time for
PWMAO and PWMBO
FTA, FTB
390
ns
7
ns
6
ns
Single 390ns pulse, 10% to 90%
PWMAO to PWMBO
Rise Time Matching
Single 390ns pulse
-4
+4
ns
PWMAO to PWMBO
Fall Time Matching
Single 390ns pulse
-2
+2
ns
PWMAO to PWMBO
Delay Matching
Single 390ns pulse, measured at 50% FSR of
rising edges
-30
+30
ns
PWMAO and PWMBO
Pulse Width Accuracy
Single 390ns pulse, pulse width difference
between input and output waveforms (measured
at 50% points)
-30
+30
ns
PWMAO and PWMBO
Pulse Width Variation
vs. Temperature
Single 390ns pulse
PWMAO and PWMBO
Pulse Width Matching
Single 390ns pulse, difference between PWMAO
and PWMBO pulse widths
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25
-30
ps/°C
+30
ns
Maxim Integrated │ 6
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
Op Amps
VCCI = +3.0V to +5.5V, VGND = 0V, VCM = VOUT = VCCI/2, no resistive load, CL = 10pF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25°C, VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
OP1, OP2
STATIC
Supply Voltage
VCCI Supply Rejection
Ratio
VCC Supply Rejection
Ratio
VCCI
Guaranteed by PSRRVCCI test
3.0
PSRRVCCI
3.0V ≤ VCCI ≤ 5.5V
62
PSRRVCC
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V
Common Mode Input
Voltage
VCMR
Common Mode
Rejection Ratio
CMRR
Input Offset Voltage
VOS
Input Offset Voltage
Drift
∆VOS
Input Bias Current
Input Offset Current
Open-Loop Gain
IB
IOS
AVOL
80
dB
165
dB
Guaranteed by CMRR test
VCCI ≤ 4.5V
-0.1
VCCI 0.5
V
Guaranteed by CMRR test
4.5V ≤ VCCI ≤ 5.5V
-0.1
+4.0
V
-0.1V ≤ VCM ≤ min (4.0V, VCCI - 0.5V)
56
dB
1
(Note 2)
mV
15
µV/°C
-40°C ≤ TA ≤ +85°C (Note 2)
-15
+15
pA
-40°C ≤ TA ≤ +125°C (Note 2)
-125
+125
pA
-40°C ≤ TA ≤ +85°C (Note 2)
-15
+15
pA
-40°C ≤ TA ≤ +125°C (Note 2)
-80
+80
pA
150mV ≤ VOUT ≤ VCCI - 150mV,
RL = 100kΩ connected to VCCI / 2,
-40°C ≤ TA ≤ +85°C
78
-40°C ≤ TA ≤ +125°C
72
dB
Output Voltage High
VOH
VCCI – VOUT,
RL = 100kΩ connected to VCCI / 2
25
mV
Output Voltage Low
VOL
VOUT - VGND,
RL = 100kΩ connected to VCCI / 2
25
mV
Output Short-Circuit
Current
IOUT(SC)
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±3
mA
Maxim Integrated │ 7
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
Op Amps (continued)
VCCI = +3.0V to +5.5V, VGND = 0V, VCM = VOUT = VCCI/2, no resistive load, CL = 10pF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25°C, VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC
Input Voltage Noise
Density
eN
f = 1kHz
150
nV/√Hz
Input Current Noise
Density
iN
f = 1kHz
40
fA/√Hz
200
kHz
Gain Bandwith Product
Slew Rate
GBWP
SR
Settling Time
Maximum Capacitive
Load
CL
0.1
V/ µs
To 0.1%, VOUT = 2V step, AV = -1V/V
25
µs
No sustained oscillations, AV = 1V/V
100
pF
OP3 (RL = 100kΩ CONNECTED to VCCI/2, CL = 20pF)
STATIC
Supply Voltage
VCCI
Guaranteed by PSRRVCCI test
3.0
107
VCCI Supply Rejection
Ratio
PSRRVCCI
3.0V ≤ VCCI ≤ 5.5V
VCC Supply Rejection
Ratio
PSRRVCC
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V
Common Mode Input
Voltage
VCMR
Common Mode
Rejection Ratio
CMRR
Input Offset Voltage
VOS
Input Offset Voltage
Drift
∆VOS
Input Bias Current
IB
5.5
V
dB
195
dB
Guaranteed by CMRR test
VCCI ≤ 4.3V
-0.1
VCCI 0.3
V
Guaranteed by CMRR test
4.3V ˂ VCCI ≤ 5.5V
-0.1
+4.0
V
-0.1V ≤ VCM ≤ min(4.0V, VCCI - 0.3V)
105
TA = 25°C, VCCI = 3.3V (Note 2)
-10
(Note 2)
dB
5
+10
µV
70
nV/°C
-40°C ≤ TA ≤ +85°C (Note 2)
-15
+15
pA
-40°C ≤ TA ≤ +125°C (Note 2)
-125
+125
pA
Input Offset Current
IOS
-40
pA
Input Capacitance
CIN
2
pF
150
dB
Open-Loop Gain
AVOL
150mV ≤ VOUT ≤ VCCI-150mV,
RL = 5kΩ connected to VCCI / 2
Output Voltage High
VOH
VCCI – VOUT,
RL = 100kΩ connected to VCCI / 2
12
mV
Output Voltage Low
VOL
VOUT - VGND,
RL = 100kΩ connected to VCCI / 2
12
mV
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123
Maxim Integrated │ 8
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
Op Amps (continued)
VCCI = +3.0V to +5.5V, VGND = 0V, VCM = VOUT = VCCI/2, no resistive load, CL = 10pF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25°C, VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC
Input Voltage Noise
Density
f = 1kHz
35
nV/√Hz
0.1Hz ≤ f ≤ 10Hz
0.7
µVp-p
f = 1kHz
80
fA/√Hz
GBWP
2.2
MHz
SR
0.7
V/µs
57
°
300
pF
eN
Input Voltage Noise
Input Current Noise
Density
Gain Bandwidth Product
Slew Rate
iN
Phase Margin
Maximum Capacitive
Load
CL
No sustained oscillations, AV = 1V/V
Electrical Characteristics (continued)
Comparators
VCCI = +3.0V to +5.5V, VDD = +1.8V to +3.6V, VGND = 0V, VCM = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25°C, VDD = VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
3.0
5.5
V
1.8
3.6
V
COMP1, COMP2
STATIC
Supply Voltage
VCCI
Supply Voltage Output
Stage
VDD
VCCI Supply Rejection
Ratio
PSRRVCCI
3.0V ≤ VCCI ≤ 5.5V
VCC Supply Rejection
Ratio
PSRRVCC
4.3V ≤ VCC ≤ 36V, VCCI = 3.3V
Common Mode Input
Voltage
VCMR
Guaranteed by CMRR test
0
Common Mode
Rejection Ratio
CMRR
0V ≤ VCM ≤ VCCI – 1.3V
56
Input Offset Voltage
VOS
Hysteresis
VHYS
Input Bias Current
Input Offset Current
IB
CIN
Output Voltage High
VOH
54
dB
160
VCM = 0V
-10
dB
VCCI 1.3
75
-10
IOS
Input Capacitance
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Guaranteed by PSRRVCCI test
dB
+10
mV
15
mV
-1
nA
1
nA
2
VDD - VOUT, ISOURCE = 100 µA
V
pF
0.4
V
Maxim Integrated │ 9
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
Comparators (continued)
VCCI = +3.0V to +5.5V, VDD = +1.8V to +3.6V, VGND = 0V, VCM = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25°C, VDD = VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
Output Voltage Low
VOL
Short Circuit Current
ISC
CONDITIONS
MIN
TYP
VOUT – VGND, ISINK = 100 µA
MAX
UNITS
0.4
V
Short to GND
2
mA
Short to VDD
-2
mA
2
µs
DYNAMIC
Propagation Delay Low
to High
tPD+
CLOAD = 10pF, threshold set to VCCI -1.4V, input
swings from 0V to VCCI -1.3V
Propagation Delay High
to Low
tPD-
CLOAD = 10pF, threshold set to 0.1V, input
swings from VCCI -1.3V to 0V
0.5
µs
Rise Time
TR
CLOAD= 10pF
50
ns
Fall Time
TF
CLOAD= 10pF
50
ns
LDO
VCC = +4.0V to +36V, VGND = 0V, CLOAD = 0.32µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C,
VCC = +24V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4.0
24
36
V
LDO
STATIC
Supply Voltage
VCC
Guaranteed by line regulation test
Dropout Voltage
Guaranteed by line and load regulation tests
VCC Line Regulation
VCC from VCCI+1V to 36V,
ILDO = 4mA, VCCI = 3.0V to 5.5V
Output Voltage
VCCI
Output Voltage
Accuracy
Output Current Range
VCCI Current Limit
ILDO
ICCI_Limit
V
2
25
mV
Guaranteed by block PSRRVCCI tests
3.0
5.5
V
VCC = 24V, no load except for LDOFB resistor
divider, VCCI = 3.3V
-3.5
+3.5
%
4
mA
Guaranteed by load regulation test
0
VCCI short to GND
12
VCC = VCCI+1V, ILDO from 0mA to 4mA,
VCCI = 3.0V to 5.5V
1
CLOAD
No resistive load except for LDOFB resistor
divider
5
µF
PSRR
VCC = 12V, DC to 120Hz
70
dB
Load Regulation
Maximum Capacitive
Load
1
mA
10
mV
DYNAMIC
VCC Supply Rejection
Ratio
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Maxim Integrated │ 10
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Electrical Characteristics (continued)
Chip-Level Specifications
VCC = +4.0V to +36V, VCCI = +3.0V to +5.5V, VDD = +1.8V to +3.6V, VGND = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical
values are at TA = +25°C, VCC = +24V, VDD = VCCI = +3.3V. (Note 1)
PARAMETER
SYMBOL
CONDITIONS
ICC
VCC = 24V, VCCI = 3.3V, SHDN = 3.3V, no load,
-40°C ≤ TA ≤ +85°C
MIN
TYP
MAX
UNITS
170
250
µA
265
µA
STATIC
VCC Supply Current
VCC Supply Current
with PWM Conditioners
Shutdown
VDD Supply Current
ICC_SHDN
-40°C ≤ TA ≤ +125°C
VCC = 24V, VCCI = 3.3V, SHDN = 0V, no load
142
IDD
µA
1
µA
PWRGOOD Turn-on
Threshold
90
% of
VCCI
PWRGOOD Turn-off
Threshold
80
% of
VCCI
PWRGOOD Voltage
High
VOH
VCCI – VOUT, ISOURCE = 100 µA
0.4
V
PWRGOOD Voltage
Low
VOL
VOUT – VGND, ISINK = 100 µA
0.4
V
PWRGOOD Short
Circuit Current
ISC
Short to GND
2
mA
Short to VCCI
-2
mA
From VCCI crossing turn-on threshold to
PWRGOOD high
0.7
ms
DYNAMIC
PWRGOOD Turn-on
Delay
Note 1: Specifications are 100% tested at TA = +25°C (exceptions noted). All temperature limits are guaranteed by design.
Note 2: Guaranteed by design, not production tested.
0.1ms
PWMAP
PWMBP
0.1ms/256
256 STEPS
Figure 1. Typical PWM Timing Diagram
www.maximintegrated.com
Maxim Integrated │ 11
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
TRANSFER CHARACTERISTICS
LOOP CURRENT vs. PWM DUTY CYCLE
toc01
30.0
15.0
10.0
20.0
15.0
10.0
5.0
0.0
0.010
0.005
0.000
-0.005
-0.010
-0.015
0.0
10
20
30
40
50
60
70
80
90 100
0
0.5
1
1.5
2
DUTY CYCLE (%)
OP3 INPUT (V)
4-20mA LINEARITY vs.
PWM DUTY CYCLE AND
LOOP VOLTAGE
VCC SUPPLY CURRENT
(SYSTEM LEVEL)
vs. TEMPERATURE
0.020
toc04
400
VLOOP = 24V
RLOAD = 100Ω
0.015
VCC SUPPLY CURRENT (µA)
0.010
0.005
0.000
-0.005
-0.010
-0.015
16V
24V
32V
36V
0
toc05
350
300
300
250
200
150
100
12mA
0
20
40
60
toc07
VBACKUP
200
150
100
16
toc08
12mA
20mA
21
26
31
VCC SUPPLY REJECTION
RATIO vs. FREQUENCY
(SYSTEM LEVEL)
70
18
36
toc09
60
16
50
14
12
10
8
6
40
30
20
4
10
2
1
10
100
1k
FREQUENCY (Hz)
www.maximintegrated.com
toc06
VCC VOLTAGE (V)
0
100ms/div
80
RLOAD = 100Ω
4mA
PSRR (dB)
10mV/div
LOOP CURRENT NOISE DENSITY (nA/√Hz)
VINSIDE
60
250
20 35 50 65 80 95 110 125
4mA LOOP CURRENT NOISE
DENSITY vs. FREQUENCY
OVER 500Ω LOAD
20
VOUTN
40
VCC SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TEMPERATURE (°C)
PWM DUTY CYCLE (%)
4mA LOOP CURRENT NOISE
DURING SILENCE
OVER 500Ω LOAD
125°C
0
-40 -25 -10 5
80
85°C
50
20mA
0
-0.020
20
400
350
4mA
25°C
PWM DUTY CYCLE (%)
RLOAD = 100Ω
50
-40°C
-0.020
2.5
VCC SUPPLY CURRENT (µA)
0
toc03
VLOOP = 24V
RLOAD = 100Ω
0.015
LOOP CURRENT LINEARITY (%FS)
LOOP CURRENT (mA)
LOOP CURRENT (mA)
20.0
0.020
VLOOP = 24V
RLOAD = 250Ω
25.0
5.0
LOOP CURRENT LINEARITY (%FS)
toc02
30.0
VLOOP = 24V
RLOAD = 250Ω
25.0
4-20mA LINEARITY vs.
PWM DUTY CYCLE
AND TEMPERATURE
TRANSFER CHARACTERISTICS
LOOP CURRENT vs. OP3 INPUT
10k
100k
0
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Maxim Integrated │ 12
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
LOOP SUPPLY REJECTION
RATIO vs. FREQUENCY
(SYSTEM LEVEL)
70
20mASTEP TRANSIENT
RESPONSE OVER 500Ω LOAD
toc10
toc11
PSRR (dB)
60
50
VOUTN
40
VINSIDE
30
VBACKUP
2V/div
20
10
0
10
100
1k
10k
100k
1M
20ms/div
FREQUENCY (Hz)
ANALOG RATE OF CHANGE
OVER 500Ω LOAD
WITH DIGITAL FILTER
HART COMMUNICATION
toc12
toc13
VOUTN
VOUTN
VINSIDE
VINSIDE
200mV/div
10x gain
(AC
COUPLED)
VBACKUP
200mV/div
(ACCOUPLED)
VBACKUP
2ms/div
20ms/div
10kHZ SQUARE WAVE
OVER 100Ω LOAD
OP1/OP2 INPUT OFFSET
VOLTAGE HISTOGRAM
toc14
30
toc15
25
VINSIDE
100mV/div
(ACCOUPLED)
VBACKUP
FREQUENCY (%)
VOUTN
20
15
10
5
0
50µs/div
-1800 -1200
-600
0
600
1200
1800
INPUT OFFSET VOLTAGE (µV)
www.maximintegrated.com
Maxim Integrated │ 13
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
VCCI = 5.5V
VCM = 2.75V
TA = +25°C
30
FREQUENCY (%)
25
20
15
10
800
INPUT OFFSET VOLTAGE (µV)
35
OP1/OP2 INPUT OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE
400
200
0
-200
0
-600
-0.1
0.08
0.12
0.16
0.4
0.9
85°C
1.4
125°C
1.9
10
2.4
-40
-60
-80
-100
-40°C
-140
0
2.9
3.297
3.296
3.295
0.5
25°C
1
85°C
1.5
125°C
2
2.5
3
INPUT COMMON-MODE VOLTAGE (V)
toc20
GAIN
120
8
100
7
80
6
60
5
OP1/OP2 GAIN AND PHASE
vs. FREQUENCY
140
RLOAD = 100kΩ
9
OUTPUT VOLTAGE (mV)
OUTPUT VOLTAGE (V)
25°C
OP1/OP2 OUTPUT VOLTAGE
LOW vs. TEMPERATURE
toc19
3.298
toc21
AV = 1V/V
RLOAD = 100kΩ
CLOAD = 10pF
225
180
135
90
45
PHASE
40
0
20
-45
3
0
-90
3.292
2
-20
-135
3.291
1
-40
-180
3.290
0
-60
3.294
3.293
-40 -25 -10 5
4
20 35 50 65 80 95 110 125
-40 -25 -10 5
TEMPERATURE (°C)
-225
10m 100m
20 35 50 65 80 95 110 125
1
10000
toc22
VCCI = 3.3V
VCM = 1.65V
AV = 1V/V
RLOAD = ∞
OP1/OP2 SMALL-SIGNAL
PULSE RESPONSE
1.80
100
100
1k
10k 100k 1M
1.70
1.65
1.60
OP1/OP2 LARGE-SIGNAL
PULSE RESPONSE
2.97
toc24
AV = 1V/V
CLOAD = 15pF
2.64
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
UNSTABLE
toc23
AV = 1V/V
CLOAD = 15pF
1.75
1000
10
FREQUENCY (Hz)
TEMPERATURE (°C)
OP1/OP2 CAPACITIVE LOAD
vs. ISOLATION RESISTOR
CAPACITANCE (pF)
0
-20
INPUT COMMON-MODE VOLTAGE (V)
RLOAD = 100kΩ
3.299
-40°C
GAIN (dB)
3.300
20
-120
INPUT BIAS CURRENT (pA)
OP1/OP2 OUTPUT VOLTAGE
HIGH vs. TEMPERATURE
toc18
40
-400
0.04
OP1/OP2 INPUT BIAS CURRENT
vs. COMMON-MODE VOLTAGE
60
600
5
0
toc17
PHASE (°)
toc16
INPUT BIAS CURRENT (pA)
OP1/OP2 INPUT BIAS
CURRENT HISTOGRAM
2.31
1.98
1.65
1.32
0.99
1.55
0.66
1.50
10
0.1
1
10
100
ISOLATION RESISTOR (Ω)
www.maximintegrated.com
1000
10000
0.33
0
10
20
30
40
50
60
TIME (µs)
70
80
90 100
0
10
20
30
40
50
60
70
80
90 100
TIME (µs)
Maxim Integrated │ 14
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
OP1/OP2 VCCI SUPPLY REJECTION
RATIO vs. FREQUENCY
toc26
90
AV = 4V/V
1000
PSRR (dB)
100
80
160
70
140
60
120
50
40
0.01
0.1
1
10
60
20
40
10
20
1
10
100
OP3 INPUT OFFSET
VOLTAGE HISTOGRAM
25
1k
10k
toc28
FREQUENCY (%)
15
10
15
10
5
5
0
0
-4.6
-4.0
-3.4
-2.8
-2.2
3
3.42
3.53
3.64
3.75
3.301
-40
-60
-80
-100
-120
toc32
0
0.5
25°C
1
1.5
85°C
2
-5
-7
2.5
-40°C
0.3
25°C
0.7
1.1
1.5
85°C
1.9
125°C
2.3
2.7
3.1
OP1/OP2 OUTPUT VOLTAGE
LOW vs. TEMPERATURE
toc33
RLOAD = 100kΩ
0.9
0.8
3.299
3.298
3.297
0.7
0.6
0.5
0.4
0.3
0.2
0.1
125°C
INPUT COMMON-MODE VOLTAGE (V)
www.maximintegrated.com
-3
1
RLOAD = 100kΩ
3.296
-40°C
100k
INPUT COMMON-MODE VOLTAGE (V)
OUTPUT VOLTAGE (mV)
OUTPUT VOLTAGE (V)
-20
10k
OP3 INPUT OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE toc30
-0.1
3.300
0
1k
-1
3.86
OP3 OUTPUT VOLTAGE
HIGH vs. TEMPERATURE
20
-160
100
1
INPUT BIAS CURRENT (pA)
OP3 INPUT BIAS CURRENT
vs. COMMON-MODE VOLTAGE toc31
-140
10
-9
3.31
INPUT OFFSET VOLTAGE (µV)
40
toc29
VCCI = 5.5V
VCM = 2.75V
TA = +25°C
20
-5.2
1
FREQUENCY (Hz)
OP3 INPUT BIAS
CURRENT HISTOGRAM
25
20
-5.8
0
100k
FREQUENCY (Hz)
FREQUENCY (kHz)
FREQUENCY (%)
80
30
100
OP1/OP2 VCC SUPPLY REJECTION
RATIO vs. FREQUENCY
toc27
100
0
10
INPUT BIAS CURRENT (pA)
180
INPUT OFFSET VOLTAGE (µV)
INPUT VOLTAGE NOISE (nV/√Hz)
10000
toc25
PSRR (dB)
OP1/OP2 INPUT VOLTAGE
NOISE vs. FREQUENCY
3.295
3
0
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated │ 15
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
140
GAIN (dB)
120
270
180
135
80
90
45
PHASE
40
0
20
-45
0
-90
-20
VCCI = 3.3V
VCM = 1.65V
AV = 1V/V
RLOAD = 100kΩ
225
100
60
10000
OP3 SMALL-SIGNAL
PULSE RESPONSE
1.80
1.75
1000
UNSTABLE
toc36
AV = 1V/V
CLOAD = 15pF
1.70
1.65
1.60
1.55
-135
-40
-180
10m 100m 1
10
100
1k
1.50
100
10k 100k 1M 10M
0.1
1
FREQUENCY (Hz)
10
100
1000
0
10000
10
20
OP3 INPUT VOLTAGE
NOISE vs. FREQUENCY
toc37
30
40
50
60
70
80
90 100
TIME (µs)
ISOLATION RESISTOR (Ω)
OP3 LARGE-SIGNAL
PULSE RESPONSE
2.97
OP3 0.1Hz TO 10Hz
INPUT VOLTAGE NOISE
toc38
10000
toc39
AV = 1V/V
CLOAD = 15pF
INPUT VOLTAGE NOISE (nV/√Hz)
2.64
OUTPUT VOLTAGE (V)
toc35
OUTPUT VOLTAGE (V)
AV = 1V/V
RLOAD = 100kΩ
CLOAD = 20pF
GAIN
OP3 CAPACITIVE LOAD
vs. ISOLATION RESISTOR
CAPACITANCE (pF)
160
toc34
PHASE (°)
OP3 GAIN AND PHASE
vs. FREQUENCY
2.31
1.98
1.65
1.32
0.99
1000
0.1µV/div
100
0.66
0.33
10
0
10
20
30
40
50
60
70
80
90 100
0.01
0.1
TIME (µs)
OP3 VCCI SUPPLY REJECTION
RATIO vs. FREQUENCY
120
toc40
10
1s/div
100
OP3 VCC SUPPLY REJECTION
RATIO vs. FREQUENCY
200
110
toc41
VOLTAGE REFERENCE
LINE REGULATION
2.5030
toc42
180
100
2.5025
OUTPUT VOLTAGE (V)
160
90
140
80
70
PSRR (dB)
PSRR (dB)
1
FREQUENCY (kHz)
60
50
40
120
100
80
60
30
40
20
2.5020
2.5015
2.5010
2.5005
20
10
0
0
1
10
100
1k
10k
FREQUENCY (Hz)
www.maximintegrated.com
100k
1M
2.5000
1
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
3
-40°C
25°C
3.5
4
85°C
4.5
125°C
5
5.5
VCCI (V)
Maxim Integrated │ 16
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
2.5020
2.5020
2.5015
2.5015
2.5010
2.5005
2.5000
2.4995
VOLTAGE REFERENCE
LOAD REGULATION
2.5025
VCCI = 5.5V
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
2.5025
toc43
toc44
35
VCCI = 3.0V
25
2.5010
2.5005
2.5000
2.4990
-40°C
2.4985
0
25
25°C
100
200
85°C
300
400
25°C
85°C
125°C
2.4985
500
15
5
-40°C
125°C
20
10
2.4995
2.4990
VOLTAGE REFERENCE TEMPERATURE
COEFFICIENT HISTOGRAM
toc45
30
FREQUENCY (%)
VOLTAGE REFERENCE
LOAD REGULATION
0
100
200
300
400
ILOAD (µA)
ILOAD (µA)
VOLTAGE REFERENCE TEMPERATURE
HYSTERESIS HISTOGRAM
toc46
VOLTAGE REFERENCE LINE
TRANSIENT RESPONSE
500
0
0.4
1.3
2.2
3.1
4.0
4.9
5.8
TEMPERATURE COEFFICIENT (ppm/°C)
VOLTAGE REFERENCE LOAD
TRANSIENT RESPONSE
toc47
toc48
+20V
VVCC
2V/div
FREQUENCY (%)
20
+25µA
ILOAD
25µA/div
-25µA
15
+10V
10
VREFO
20mV/div
VREFO
10mV/div
5
AC-COUPLED
CLDO = 0.32µF
AC-COUPLED
0
-278
-234
-190
-146
-102
-58
100µs/div
-14
20µs/div
TEMPERATURE HYSTERESIS (ppm)
100
VOLTAGE REFERENCE VCCI REJECTION
RATIO vs. FREQUENCY
toc49
180
90
toc51
160
80
140
70
120
60
PSRR (dB)
PSRR (dB)
VOLTAGE REFERENCE
0.1Hz TO 10Hz OUTPUT NOISE
VOLTAGE REFERENCE VCC REJECTION
RATIO vs. FREQUENCY
toc50
50
40
100
10µV/div
80
60
30
20
40
10
20
0
1
10
100
1k
10k
FREQUENCY (Hz)
www.maximintegrated.com
100k
1M
0
1
10
100
1k
10k
100k
1M
1s/div
FREQUENCY (Hz)
Maxim Integrated │ 17
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
toc52
10.0
1.0
PWMA/PWMB INPUT THRESHOLD
VOLTAGE vs. TEMPERATURE
1.001
INPUT THRESHOLD VOLTAGE (V)
VOLTAGE REFERENCE NOISE (µV/√Hz)
100.0
0.01
0.00
toc54
-0.05
1.000
0.999
0.998
0.1
1
10
-0.10
-0.15
-0.20
-0.25
-0.30
-0.40
0.997
100
-40 -25 -10 5
FREQUENCY (kHz)
-40 -25 -10 5
20 35 50 65 80 95 110 125
PWMA/PWMB OUTPUT VOLTAGE
HIGH vs. TEMPERATURE
toc55
PWMA/PWMB OUTPUT VOLTAGE
LOW vs. TEMPERATURE
2
RLOAD = 100kΩ
2.500
toc56
OUTPUT VOLTAGE (mV)
1.6
2.499
2.498
2.497
1.4
1.2
1
0.8
0.6
0.4
2.496
0.2
2.495
20 35 50 65 80 95 110 125
-40 -25 -10 5
TEMPERATURE (°C)
-40°C
-0.04
-0.06
-40 -25 -10 5
25°C
85°C
toc59
OUTPUT VOLTAGE (mV)
0.02
0.00
-0.02
-0.04
8
6
4
-0.08
0
20 35 50 65 80 95 110 125
2.496
10
2
toc60
2.498
12
-0.06
20 35 50 65 80 95 110 125
PWMA/PWMB OUTPUT VOLTAGE
HIGH vs. LOAD CURRENT
2.500
125°C
14
0.04
www.maximintegrated.com
-0.02
TEMPERATURE (°C)
PWMA/PWMB OUTPUT VOLTAGE
LOW vs. LOAD CURRENT
16
RL = 100kΩ
TEMPERATURE (°C)
0.00
TEMPERATURE (°C)
PWMA-PWMB OUTPUT LOW LEVEL
MATCHING vs. TEMPERATURE toc58
-40 -25 -10 5
0.02
20 35 50 65 80 95 110 125
OUTPUT VOLTAGE (V)
0.06
RLOAD = 100kΩ
0.04
-0.08
0
-40 -25 -10 5
PWMA-PWMB OUTPUT HIGH LEVEL
MATCHING vs. TEMPERATURE toc57
0.06
RLOAD = 100kΩ
1.8
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT VOLTAGE MATCHING (mV)
2.501
OUTPUT VOLTAGE MATCHING (mV)
PWMA/PWMB INPUT BIAS
CURRENT vs. TEMPERATURE
-0.35
0.1
OUTPUT VOLTAGE (V)
toc53
INPUT BIAS CURRENT (nA)
VOLTAGE REFERENCE
NOISE vs. FREQUENCY
2.494
2.492
2.490
2.488
2.486
2.484
2.482
-200
-150
-100
ILOAD (µA)
-50
0
-40°C
2.480
0
50
25°C
100
85°C
125°C
150
200
ILOAD (µA)
Maxim Integrated │ 18
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
-9.0
-9.5
6.0
-10.0
5.5
-10.5
5.0
-11.0
4.5
-11.5
4.0
-12.0
-40 -25 -10 5
SHORT TO VREF
2.0
2.0
1.5
1.0
INPUT
-0.5
0
200
400
TEMPERATURE (°C)
PWMA-PWMB PROPAGATION DELAY
MATCHING vs. TEMPERATURE toc64
RLOAD = 100kΩ
CLOAD = 10pF
-0.5
-1.0
-1.5
-2.0
1.4
-2.5
1.2
0
1000
PWMA-PWMB RISE AND FALL TIME
MATCHING vs. TEMPERATURE toc65
RISE TIME MATCHING
0.6
FALL TIME MATCHING
0.4
0.2
0.0
0.15
0.35
0.30
0.25
0.20
0.15
0.10
0.00
6
7
toc66
1.0
0.5
0.0
-0.5
5% DUTY CYCLE
50% DUTY CYCLE
95% DUTY CYCLE
-1.5
-40 -25 -10 5
COMP1/COMP2 INPUT BIAS
CURRENT vs. TEMPERATURE
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
toc68
COMP1/COMP2 OUTPUT VOLTAGE
LOW vs. LOAD CURRENT
toc69
350
-40°C
25°C
85°C
125°C
300
0.05
0.00
-0.05
-0.10
-0.15
250
200
150
100
50
-0.25
20 35 50 65 80 95 110 125
5
1.5
20 35 50 65 80 95 110 125
-0.20
0.05
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2.0
-1.0
OUTPUT VOLTAGE (mV)
INPUT BIAS CURRENT (nA)
0.40
OUTPUT
4
RLOAD = 100kΩ
CLOAD = 10pF
PERIOD = 100µs
TEMPERATURE (°C)
toc67
3
2.5
0.10
TEMPERATURE (°C)
2
PWMA-PWMB PULSE WIDTH
MATCHING vs. TEMPERATURE
3.0
RLOAD = 100kΩ
CLOAD = 10pF
-40 -25 -10 5
0.45
-40 -25 -10 5
1
TIME (µs)
0.8
20 35 50 65 80 95 110 125
COMP1/COMP2 INPUT OFFSET
VOLTAGE vs. TEMPERATURE
INPUT
-0.5
800
1.0
TEMPERATURE (°C)
INPUT OFFSET VOLTAGE (mV)
600
-0.2
-40 -25 -10 5
0.50
OUTPUT
TIME (ns)
RISE AND FALL TIME MATCHING (ns)
PROPAGATION DELAY MATCHING (ns)
0.0
1.0
0.0
0.0
-13.0
1.5
0.5
0.5
20 35 50 65 80 95 110 125
toc63
CODE = 10
CLOAD = 10pF
2.5
PULSE WIDTH MATCHING (ns)
3.0
SHORT TO GND
PWMA/PWMB INPUT/OUTPUT
WAVEFORMS
3.0
CODE = 1
CLOAD = 10pF
2.5
-12.5
3.5
toc62
VOLTAGE (V)
6.5
PWMA/PWMB INPUT/OUTPUT
WAVEFORMS
3.0
VOLTAGE (V)
toc61
CURRENT FROM VREF (mA)
CURRENT TO GND (mA)
7.0
PWMA/PWMB SHORT-CIRCUIT
CURRENT vs. TEMPERATURE
0
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
-200
-150
-100
-50
0
ILOAD (µA)
Maxim Integrated │ 19
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
2.12
3.30
CURRENT TO GND (mA)
3.20
3.15
3.10
3.00
-40°C
2.95
0
25°C
50
85°C
100
125°C
2.08
-2.02
2.06
-2.04
2.04
-2.06
2.02
-2.08
2.00
-2.10
SHORT TO GND
1.98
150
-40 -25 -10 5
200
COMP1/COMP2 INPUT/OUTPUT
WAVEFORMS (TPD-)
3.5
NEGATIVE INPUT
OUTPUT
2.0
1.5
1.0
0.5
1
1.25
toc74
LOW TO HIGH
HIGH TO LOW
1000
0.5
1
1.5
3.325
3.315
3.310
3.305
-40°C
3.290
4
8
25°C
12
16
3.310
3.305
3.300
20
85°C
24
125°C
28
32
36
VCC (V)
LDO LOAD REGULATION
toc77
3.318
LDO OUTPUT VOLTAGE
vs. TEMPERATURE
toc78
3.316
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.315
toc75
3.320
20 35 50 65 80 95 110 125
3.320
3.320
3
3.295
3.324
ILDO = 4mA
2.5
3.300
-40 -25 -10 5
toc76
2
ILDO = 0.1mA
TEMPERATURE (°C)
LDO LINE REGULATION
1.5
LDO LINE REGULATION
3.330
800
TIME (µs)
3.330
0
3.325
1200
400
0.75
-0.5
TIME (µs)
1400
600
0.5
0.0
-2.12
1600
0.0
0.25
1.5
0.5
1800
-0.5
0
OUTPUT
2.0
1.0
CLOAD = 10pF
2000
POSITIVE INPUT
2.5
NEGATIVE INPUT
2.5
20 35 50 65 80 95 110 125
COMP1/COMP2 PROPAGATION
DELAY vs. TEMPERATURE
2200
PROPAGATION DELAY (ns)
VOLTAGE (V)
toc73
CLOAD = 10pF
3.0
POSITIVE INPUT
3.0
TEMPERATURE (°C)
ILOAD (µA)
4.0
SHORT TO VDD
toc72
CLOAD = 10pF
3.5
-2.00
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.25
COMP1/COMP2 INPUT/OUTPUT
WAVEFORMS (TPD+)
4.0
-1.98
2.10
3.05
OUTPUT VOLTAGE (V)
toc71
VOLTAGE (V)
3.35
COMP1/COMP2 SHORT-CIRCUIT
CURRENT vs. TEMPERATURE
CURRENT FROM VDD (mA)
COMP1/COMP2 OUTPUT VOLTAGE
HIGH vs. LOAD CURRENT
toc70
3.316
3.312
3.308
3.304
3.314
3.312
3.310
3.308
3.306
3.304
3.300
3.295
-40°C
3.290
4
8
12
25°C
16
20
VCC (V)
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85°C
24
-40°C
125°C
28
32
25°C
85°C
3.296
36
0.1mA LOAD
3.302
125°C
4mA LOAD
3.300
0
0.5
1
1.5
2
ILDO (mA)
2.5
3
3.5
4
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated │ 20
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Typical Operating Characteristics (continued)
VCC = +24V, VDD = VCCID = VCCI = +3.3V, GND = 0V, op amp VCM = VOUT = VCCI/2, op amp CL = 15pF, comparator and PWM
CL = 10pF, LDO CLOAD = 0.32µF, no resistive load on any output, TA = +25°C, unless otherwise noted.
LDO LINE
TRANSIENT RESPONSE
LDO LOAD
TRANSIENT RESPONSE
toc79
toc80
+15V
+4.0mA
ILDO
2mA/div
80
+0.4mA
+9V
LOAD CURRENT
VCCI
VVCCI
20mV/div
toc81
CLOAD = 0.32µF
R1 = 510kΩ
R2 = 300kΩ
90
70
PSRR (dB)
VVCC
2V/div
LDO VCC SUPPLY REJECTION
RATIO vs. FREQUENCY
100
VVCCI
20mV/div
60
50
40
30
20
VCC
AC-COUPLED
CLOAD = 0.32µF
VCCI
AC-COUPLED
CLOAD = 0.32µF
10
0
100µs/div
1
40µs/div
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
QUIESCENT CURRENT
vs. VCC VOLTAGE
195
185
200
175
190
180
170
160
165
155
145
135
8
12
16
20
85°C
24
125°C
28
32
4
36
0
13
12
VCCI
11
10
REFO
9
PWRGOOD
8
VCC
7
6
5
4
3
2
1
0
-1
100 200 300 400 500 600 700 800 900 1000
TIME (µs)
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OUTPUT VOLTAGE (V)
toc85
VCC (V)
POWER-UP WAVEFORMS
(VCC, VCCI, REFO, PWRGOOD)
190
180
170
160
8
12
25°C
16
20
85°C
24
125°C
28
32
140
36
-40 -25 -10 5
VCC (V)
VCC (V)
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
200
150
-40°C
105
POWER-UP WAVEFORMS
(VCC, VCCI, OP1O, OP2O, OP3O)
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
0
toc86
13
12
VCCI
11
OPAMP AV = 1V/V
OP1O
10
VOP1P = 2.5V
OP2O
VOP2P = 1.5V
9
OP3O
VOP3P = 1.65V
8
VCC
7
6
5
4
3
2
1
0
-1
100 200 300 400 500 600 700 800 900 1000
TIME (µs)
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
4
25°C
VCC (V)
-40°C
130
toc84
210
115
140
QUIESCENT CURRENT
vs. TEMPERATURE
220
PWM CONDITIONERS
SHUT DOWN
125
150
OUTPUT VOLTAGE (V)
toc83
POWER-UP WAVEFORMS
(VCC, VCCI, PWMAO, COMP1O)
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
0
toc87
13
12
VCCI
11
PWMAO
10
9
COMP1O
8
VCC
7
6
5
4
3
2
1
0
-1
100 200 300 400 500 600 700 800 900 1000
TIME (µs)
Maxim Integrated │ 21
VCC (V)
210
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
220
toc82
SUPPLY CURRENT (µA)
QUIESCENT CURRENT
vs. VCC VOLTAGE
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
OP3O
OP3N
OP3P
18
17
OP2O
23 22 21 20 19
OP2N
24
OP2P
PWRGOOD
TOP VIEW
OP1P
Pin Configuration
OP1N
25
16 I/C
OP1O
26
15 I/C
14 I/C
COMP2N
32
11 VCCI
10 VCCID
EP
+
9 N/C
1
2
3
4
5
6
7
8
LDOFB
PWMBP
31
VCC
30
12 REFGND
VDD
PWMAP
13 REFO
MAX12900
COMP1O
29
COMP1P
PWMBO
COMP2O
28
COMP1N
27
COMP2P
SHDN
PWMAO
Pin Description
PIN #
NAME
DESCRIPTION
1
COMP2P
Comparator 2 noninverting input
2
COMP1N
Comparator 1 inverting input
3
COMP1P
Comparator 1 noninverting input
4
COMP2O
Comparator 2 output
5
COMP1O
Comparator 1 output
6
VDD
Comparator Output Supply Voltage. Add a 0.1µF bypass cap from VDD to GND.
7
VCC
Positive Supply Voltage at Internal LDO Input. Add a 1µF bypass cap from VCC to GND.
8
LDOFB
9
N/C
10
VCCID
LDO feedback voltage. Connect to resistor divider between VCCI and GND.
Not connected
Digital power input. Connect this pin to VCCI.
11
VCCI
12
REFGND
13
REFO
14
I/C
Internally connected pin. Connect this pin to GND.
15
I/C
Internally connected pin. Connect this pin to GND.
16
I/C
Internally connected pin. Connect this pin to GND.
17
OP3P
Op Amp 3 noninverting input
18
OP3N
Op Amp 3 inverting input
19
OP3O
Op Amp 3 output
20
OP2O
Op Amp 2 output
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LDO output. Add a 0.22µF bypass cap from VCCI to GND.
Internal reference ground. Connect to GND.
Internal reference output.
Maxim Integrated │ 22
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Pin Description (continued)
PIN #
NAME
DESCRIPTION
21
OP2N
Op Amp 2 inverting input
22
OP2P
Op Amp 2 noninverting input
23
PWRGOOD
24
OP1P
Op Amp 1 non-inverting input
25
OP1N
Op Amp 1 inverting input
26
OP1O
Op Amp1 output
27
SHDN
Active-Low, Shutdown Input for PWM Conditioners. PWM circuitry powers down and outputs go to
Hi-Z state when this pin is low.
28
PWMAO
PWM conditioner output A
29
PWMBO
PWM conditioner output B
30
PWMAP
PWM conditioner input A
31
PWMBP
PWM conditioner input B
32
COMP2N
Comparator 2 inverting input
EP
GND
Active-high output signal that indicates when the MAX12900 is ready.
Exposed pad, chip ground.
Detailed Description
The MAX12900 is an ultra-low-power, highly integrated
4-20mA transmitter. The MAX12900 integrates ten building
blocks in a small package: a wide supply voltage range
LDO, two comparators for PWM conditioning (PWMA and
PWMB), two low-drift, general purpose op amps (OP1
and OP2), one zero-drift, wide-bandwidth op amp (OP3),
two diagnostic comparators (COMP1 and COMP2), a
power-up sequencer with power good output, and a lowdrift voltage reference. There are many ways that one
can connect these building blocks to optimize overall
functionality and performance of the MAX12900 for a
specific application.
Power-Up Sequencer
The power-up sequencer keeps all op amp and PWM outputs at
Hi-Z, and outputs of the comparators low during power-up
until VCCI reaches 90% of its final value. After that, the
PWRGOOD signal is asserted and all outputs become
controlled by their inputs. The PWRGOOD signal is
delayed by 0.7ms (typ) after VCCI reaches 90% of its
final value, thus allowing for external loops controlled by
the MAX12900 to stabilize before signaling that the part
is ready.
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Note that external components, such as a sensor or
microcontroller, should not draw load current from VCCI
until the PWRGOOD signal has been asserted.
PWM Conditioners
The PWM conditioners generate ground level when the
input is below the threshold voltage, and generate VREF
when the input is above the threshold voltage. The PWM
conditioners can be powered down by setting the SHDN
pin low. The PWM outputs are Hi-Z during shutdown.
General Purpose Op Amps (OP1, OP2)
The general purpose op amps, OP1 and OP2, feature a
low operating supply voltage, low input bias current, railto-rail outputs, and a maximized ratio of Gain Bandwidth
Product (GBWP) to supply current. These CMOS devices
feature ultra-low input bias current up to 15pA at 85°C.
They are unity-gain stable with a 200kHz GBWP, driving
capacitive loads up to 100pF. The input common mode
voltage range can extend 100mV below ground with
excellent common-mode rejection. The OP1 and OP2 op
amps can drive the output to within 25mV of both supply
rails with a 100kΩ load. Op amp settling time depends
primarily on the output voltage and is slew-rate limited.
The general-purpose op amps can be used as PWM
filters, linear filters/amplifiers, or as linear or shunt regulator
controllers, refer to the Application Information section.
Maxim Integrated │ 23
MAX12900
Ultra-Low-Power 4-20mA Sensor Transmitter
Zero-Drift High Bandwidth Op Amp (OP3)
The zero-drift, wide bandwidth op amp OP3 uses an
innovative auto-zero technique that allows precision and
low noise with a minimum amount of power. The ultralow input offset voltage, offset drift, and 1/f noise allow
for building a highly accurate current transmitter. The
high GBWP allows for noise suppression over a wider
frequency band. The OP3 amplifier achieves rail-to-rail
performance at the output.
Driving large capacitive loads can cause instability in
many op amps. The OP3 amplifier is stable with capacitive
loads up to 300pF. Stability with higher capacitive loads
can be improved by adding an isolation resistor in series
with the op amp output.
Low-Drift 2.5V Voltage Reference
The precision bandgap reference uses a proprietary
curvature-correction circuit and laser-trimmed thin-film
resistors, resulting in a low temperature coefficient of
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