MAX78700 Multichannel, Isolated, Precision ADC
General Description
The MAX78700 is an isolated analog-to-digital converter
(ADC) for use with a compatible MAX78xxx energy mea-
surement processor. The device provides current and
voltage measurements to the host while the host pro-
vides control, command, and power to the MAX78700. A
pulse transformer provides the isolated data and power
path between the device and host, eliminating the need
for additional isolation components in the measurement
subsystem.
Applications
● SmartGrid-FriendlyEquipment
● LightingControlSystems
● CommercialandIndustrialAutomation
● RenewableEnergySystems
● ElectricVehicleChargingSystems
Benets and Features
● BetterThan0.5%Watt-HourAccuracyOverWide
DynamicRangeUsingaSingleCalibrationPoint
• High-ResolutionDelta-SigmaADC
• Factory-TrimmedVoltageReferenceandDie
TemperatureSensor
● SimplifiedSystemArchitecture
• NoPowerSupplyRequired
• FullyPoweredbytheHostwiththeIsolation
Transformer
• EliminatesDataIsolationComponents
• ReducedFormFactorandBillofMaterials
● Small10-PinμMAX®Package
19-6565; Rev 0; 12/12
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part, refer
to www.maximintegrated.com/MAX78700.related.
Block Diagram
µMAX is a registered trademark of Maxim Integrated Products, Inc.
INAP
INAN
INBP
INBN
ISOP
ISON
ENERGY
MEASUREMENT
PROCESSOR
“HOST”
RESISTIVE
SENSORS
POWER, TIMING,
CONTROL
ADC DATA
MUX
ADC
SYSTEM POWER
HOST INTERFACE
MAX78700
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MAX78700 Multichannel, Isolated, Precision ADC
(AllvoltageswithrespecttoGND.)
VoltageRangeINAN,INAP,INBP,INBN .............-0.5Vto+4.6V
VoltageRangeISOP,ISON .................................. -0.5Vto+4.6V
OperatingTemperatureRange ........................... -40°Cto+85°C
OperatingJunctionTemperature(Peak) .........................+140°C
OperatingJunctionTemperature(Peak,100ms) ............ +140°C
OperatingJunctionTemperature(Continuous) ...............+125°C
StorageTemperature ........................................ -45°Cto+165°C
LeadTemperature(soldering,10s) .................................+300°C
SolderingTemperature(reflow) ....................................... +260°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.
Absolute Maximum Ratings
Recommended External Components
Performance Specications
(Limitsare100%productiontestedatTA=+22°C.Limitsovertheoperatingtemperaturerangeandrelevantsupplyvoltagerangeare
guaranteed by design and characterization.)
Note 1: Guaranteedbydesign,notsubjecttotest.
NAME FROM TO FUNCTION VALUE UNIT
C1 VCC GND Bypasscapacitorforsupply 0.5 µF
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
UsableInputRange VIN INAP,INAN,INBP,INBN VCC -
250 VCC+
250 mV
peak
TotalHarmonicDistortion THD First10harmonics,fIN=65Hz,
VIN=20mV,64kptsFFT,
Blackman-Harriswindow -85 dB
InputImpedance fIN=65Hz 20 90 kΩ
TemperatureCoefcientofInput
Impedance fIN=65Hz(Note1) 1.7 Ω/°C
ADCGainErrorvs.
%Power-SupplyVariation VIN=200mVP-P,65Hz,
VCC=3.0V,3.6V
50 ppm/%
InputOffset -10 +10 mV
6PK IN
10 Nout 357nV / V
100 VCC / 3.3
∆
∆
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MAX78700 Multichannel, Isolated, Precision ADC
Pin Description
Pin Conguration
PIN NAME FUNCTION
1 INBN ChannelBADCNegativeInput
2INBP ChannelBADCPositiveInput
3 TESTENB EnablestheTestModes.Mustbegroundedinnormaloperation.
4 ISON TransformerNegative
5 ISOP TransformerPositive
6 TMUX Host-ControlledDIO
7VCC OutputoftheRectierBlock
8GND Ground.The0.5µFcapacitorfromVCCtoGNDmustbeconnectedtothispin.
9INAP ChannelAADCPositiveInput
10 INAN ChannelAADCNegativeInput
10
2
3
4
5
9
8
7
6
INAP
GND
VCC
TMUXISOP
ISON
TESTENB
INBP
µMAX
TOP VIEW
+
MAX78700
1INANINBN
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MAX78700 Multichannel, Isolated, Precision ADC
Detailed Description
The MAX78700 is an isolated current and voltage ana-
log-to-digital converter (ADC) that is compatible with
MAX78xxx hosts. The device digitizes low-level signals
from shunt resistor type current sensors and resistive
divider voltage measurements.
The device continuously sends ADC data to the host. The
hostcanrequestthedevicetoreturncertainancillarydata
such as trim information and die temperature data. The
MAX78700 communicates with the host through a pulse
transformer to provide isolation from the high-voltage
power domain.
Figure1showsablockdiagramofthedevicewithabrief
descriptionofvariousfunctionalblocks.
Rectier
The active rectifier in the device rectifies the power pulses
received from the host through the isolation transformer to
createtheVCCvoltage.A2.5Vregulatorblockpowersall
thedigitalblocksofthechipexceptthePLLandISO_INT,
whicharepoweredbyVCC.
ISO_INT
Theisolatedinterfaceblockreceivestheincomingdata
fromthehostandtransmitsdatabacktothehostthrough
the isolation transformer.
PLL
ThePLLlockstotheincomingpowerpulsestocreateref-
erenceclocksfortheADCandcommunicationsinterface
to the host.
ADC
MaximIntegrated’sprovendelta-sigmaADCdigitizesthe
voltage and current-sense voltages.
Bandgap
The device includes an on-chip precision bandgap volt-
agereferencethatincorporatesauto-zerotechniquesas
well as production trims to minimize errors caused by
component mismatch and drift. The result is a voltage
output with a predictable temperature coefficient that is
compensated in firmware by the host.
Figure 1. Functional Diagram
MUX
INBN
INBP
INAN
INAP
TMUX
FIR
VREF
VBIAS
GEN
IBIAS
GEN
MUX
CONTROL
TEMP
SENSE
TESTENB
ADC
MAX78700
RECTIFIER
PLL
TRIM
OTP
GND
ISOP
ISON
V
CC
2.5V
REG
2.5V
ISO_INT INTERFACE +
MODE CONTROL
CLOCK
GEN
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MAX78700 Multichannel, Isolated, Precision ADC
Package Information
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.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Ordering Information
Temperature and Power-Supply
Voltage Measurement
The device includes an on-chip temperature sensor. The
voltage from this sensor is measured by the ADC and
sent to the host. During manufacturing test, the circuit is
calibrated by measuring the voltage at room temperature
andstoringthevalueintheOTPmemory.
A resistor-divider scales the rectified power-supply voltage,
VCC, to match the input range of the ADC. The ADC mea-
sures the scaled voltage and the value is sent to the host.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10µMAX U10+2 21-0061 90-0330
PART TEMP RANGE PIN-PACKAGE
MAX78700+A00 -40°Cto+85°C 10µMAX
MAX78700+A00T -40°Cto+85°C 10µMAX
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2012MaximIntegratedProducts,Inc.
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MAX78700 Multichannel, Isolated, Precision ADC
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
012/12 Initialrelease —
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.