IXYS
MX8683 1 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683
10-Bit Digital Output Magnetic Flux Sensor
±200 Gauss / 20KHz Conversion Rate
Features:
• Single 5 Volt Power Supply
• Externally Configurable ±20A Bi-Direction
Current Sense per Turn
• 12-bit Serial Digital Output / 10-bit ADC
• Full Scale Magnetic Flux Intensity of ±200
Gauss
• 20K Conversions/Second
• Microcontroller Compatible
• Standard 3 Wire Serial Interface plus Chip
Select
• In System Calibration: OTP Full Scale Trim via
the Serial I/O Port
• Programmable Digital Filter Time Constant
• 4mm x 4mm 8 Lead DFN package RoHS
Compliant
Applications:
• Load Detection and Management
• Motor Control
• Power Supplies
Ordering Information
Part No. Description Qty
MX8683R DFN-8 Tube 91
MX8683RTR DFN-8 Tape & Reel 2500
General Description
The MX8683 is a 10-bit Digital Output Magnetic Flux
Sensor. The device is a complete sampled data
subsystem that converts a magnetic flux intensity of
±200 Gauss full scale into a 12-bit format digital
output word, (10-bit resolution). The sensor
operates as a slave on the serial interface with TTL-
level compatible inputs SDI (serial data input), SCK
(serial clock), and CS* (chip select, active low).
Terminal SDO is the tri-state serial data output.
An optional exponentially weighted moving average
digital filter is included that averages the 10-bit ADC
output into a 12-bit output word. The digital filter has
a transfer function equivalent to a first order low
pass filter.
The full scale trim and/or the digital filter time
constant are controllable through the serial I/O
interface and are one-time programmable through
the serial interface (once programmed, the values
are loaded at every power-on).
The MX8683 can be mounted onto a PCB or
incorporated into a magnetic assembly and then
calibrated in-system through the serial interface.
The operating voltage range is 4.5V to 5.5V.
Functional Block Diagram Typical Application Circuit
PWR
GND
Hall
Plate
I/O Reg
10-Bit A/D
SDI
SCK
SDO
CS*
Microcontroller MX8683
Power
Ground
1
7
4
5
8
PWR
CS*
SDI
SCK
GND
2SDO
MISO
Select
MOSI
SCK
MX8683 IXYS
Absolute Maximum Ratings
TA = +25°C unless otherwise noted Absolute Maximum Ratings are stress
ratings. Stresses in excess of these ratings
can cause permanent damage to the device.
Functional operation of the device at these or
any other conditions beyond those indicated
in the operational sections of this data sheet
is not implied. Exposure of the device to the
absolute maximum ratings for an extended
period may degrade the device and affect its
reliability.
Parameter Min Max Unit
Voltage (Any Pin to GND) +7 V
θJA, DFN-8 Package 30 °C/W
Operating Temperature Range -40 +85 °C
Storage Temperature Range -65 150 °C
ESD Warning
ESD (electrostatic discharge) sensitive device. Although the MX8683 features proprietary ESD protection circuitry,
permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
Electrical Characteristics
PWR= 5V, T = +25°C
Parameter Condition Min Typ Max Unit
Operating Voltage Range (PWR) 4.5 5.5 V
Supply Current (IPWR) 3 mA
Average A/D Reading Zero Magnetic Flux 2040 2048 2056 LSB
Average A/D Reading 100 Gauss, North Pole 3072 LSB
Output Noise Digital Filter Off 5.5 RMS
LSB
SCK pulse period 200 nS
SCK pulse width high or low 80 nS
CS* pulse period 50 µS
CS* falling to first SCK rising 100 nS
Last SCK falling to CS* rising 50 nS
SCK falling to SDO valid 60 nS
Digital output high PWR-0.5 V
Digital output low 0.5 V
Digital input low GND 0.8 V
Digital input high 2 PWR V
Digital input current 1 µA
MX8683 2 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
Pin Description
Pin No. Name Description
1 PWR Input Voltage Supply
2 SDO Serial Data Output
3 NC No Connect
4 SCK Serial Clock Input
5 SDI Serial Data Input
6 NC No Connect
7 GND Connect to Ground
8 CS*
Active low chip select for the serial interface. When a logic “high” is on this pin, the
MX8683 is tracking the hall input signal.
Detailed Circuit Description
The hall plate senses the magnetic field that is applied normal (perpendicular) to the package surface.
The signal from the hall plate is offset-corrected by detecting the difference between a pair of analog
samples during the acquisition time. During idle time (CS* high) the MX8683 tracks the first analog
sample. Immediately (~10 nS) after the falling edge of CS* the first sample is held. The track mode for
the second sample starts nominally 4 µS after the falling edge of CS*. Typically 12 µS after the falling
edge of CS* the second sample is held and the resulting analog value is then converted by the A/D. The
result of the A/D conversion is loaded into the I/O register at the next falling edge of CS*, in preparation
for output on SDO.
The internal acquisition and A/D timing is asynchronous to the SCK serial interface clock. The magnetic
field sampling period is controlled externally by the time between consecutive CS* falling edges. For zero
magnetic field input the nominal A/D output is 2048 decimal. North pole towards the top surface of the
MX8683 increases the A/D output count. Applications that require non-continuous one measurement at a
time operation should pulse CS* low twice, reading the data when CS* is low for the second time.
Serial Output (n)
A/D Convert (n+1)Acquisition (n+1)
A/D Convert (n)Acquisition (n)
CS*
SCK
SDO
externally controlled sampling period
13 12 11 10 987654321415 0113 12 11 10 987654321415 01
MX8683 3 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
POWER-ON RESET
The MX8683 contains a power-on reset circuit that resets all the internal flip-flops and initializes the
internal registers to zero. The MX8683 will reset if the voltage at terminal PWR drops below 3.2V to 3.8V.
SYNCHRONOUS SERIAL I/O
The MX8683 (slave) can communicate with a microcomputer (master) via a three wire plus chip select
serial interface. Chip select CS*, serial clock SCK, and serial data input SDI are output from the master
controller to the MX8683.
Serial data output SDO is driven by the MX8683 when selected by CS* = 0.
SDO is high impedance when CS* = 1.
SCK and SDI are don't care when CS* = 1.
SDI is captured by the rising edge of SCK.
SDO changes in response to the falling edge of SCK.
Read 12-bit data D[11:0] when SDI = logic 0
CS*
SCK
SDO
SDI
D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0D11
200 nS min
60 nS max
Note: When the filter is off, D1=D0=0, D2=LSB of the 10-bit ADC.
Write command timing: (Bit Field A[2:0] , B[5:0], OTP Bit Zp)
CS*
SCK
SDI B0B1B2B3B4B5A0A1A20
1Zp
The write command SDI input bit pattern is internally latched at the rising edge of
CS* and takes effect at the end of the next A/D conversion following CS* rising.
20 nS min
The exponentially weighted moving average digital filter has a transfer function equivalent to a first order
low pass filter.
The I/O timing remains exactly the same when the filter is used. No decimation is performed.
Let T = Sample interval (the time from CS* falling edge to CS* falling edge). Then bandwidth = 1/(2*pi*T).
Also if W = Sample weighting, then the digital output = W*(current sample) + (1-W)*(previous value).
At power-on the previous value is initialized to zero. A programmed change in A[2:0] does not reset the
previous value. Therefore when using the filter, multiple samples must be taken at power-on or after
changing A[2:0] before the filtered output will be correct.
MX8683 4 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
Bit field A[2:0] controls the digital filter operation:
A[2:0] Time Constant Sample Weighting
000 No Filter 1
001 T 1/2
010 3T 1/4
011 7T 1/8
100 15T 1/16
101 31T 1/32
110 63T 1/64
111 127T 1/128
Bit field B[5:0] is the full scale adjust:
Characteristics are 0.8% step size, ±25% total range.
B[5:0] = 000000 is the lowest sensitivity (highest full scale)
B[5:0] = 111111 is the highest sensitivity
One-Time Programming:
Bit Zp, when logic 1 along with A[2:0] and B[5:0] values, programs those values into the internal non-
volatile memory.
Programming a bit to logic 1 is permanent. A bit programmed to logic 1 cannot be made to go back to
logic 0.
Always send a write command with Zp = 0 and SDI = 0 immediately after the programming command.
The actual programming pulse occurs internally at the falling edge of CS* in the command following the
command in which Zp = logic 1.
The write command can be used to preview the trim bits as long as Zp is logic 0.
Examples:
The bit field B[5:0] can be programmed while the A[2:0] bit field is "000", or vice versa. For example the
total SDI bit pattern could be 10 000 001100 0000 1. This would permanently set the B[5:0] bit field to
001100 but the filter setting could still be subsequently changed by a different write command, either in
preview or programming.
The SDI bit pattern 10 010 010000 0000 0 would set the filter time constant to 3T and the full scale field
to 010000 as a preview, without making it permanent (because bit Zp = 0).
If the sample interval T = 1 mS and A[2:0] = 001 then the effective bandwidth would be 1/(2*3.14*1e-3) =
159 Hz. For this condition, if the steady state output was 2000 counts and a step input was applied that
would drive the output to 3000 counts then the digital output response would be 2000, 2500, 2750, 2875,
2937, 2968, 2984, 2992, 2996, 2998, 2999, 2999, 3000.
MX8683 5 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
Magnetic
Coil Current
CS*
Sample N Sample N+1 Result N
Acquisition Time 20µS
Figure 1
Input Stimulus for
Transient Response
Result N
Result N+1
2000
2200
2400
2600
2800
3000
3200
3400
Sample Number
Digital Output
Figure 2
Transient Response
No Filter
20µ Acquisition Time
2000
2200
2400
2600
2800
3000
3200
3400
Sample Number
Digital Output
Result N
Figure 3
Transient Response
Filter Bit Field A[2:0] = 001
20µ Acquisition Time
MX8683 6 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
Cascade Configurations
Sensor Location
MX8683 7 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 IXYS
Application Example
This application example illustrates one method of incorporating the MX8683 into a power circuit board
design. The double-sided 8oz copper traces carry 20A (10A on the top trace and 10A on the bottom
trace) around the center section of the planar E-core. The MX8683 is mounted on a small single layer
flex circuit that effectively adds a third layer. The flex also fans out the fine pitch DFN package to a pitch
compatible with the power board. The magnetic circuit consists of two ferrite E14 planar cores. The
center post of one of the cores is gapped to accommodate the MX8683 package thickness plus the flex
circuit thickness. For the 20A full scale application a gap of 47 to 52 mils is appropriate (1.2 to 1.32 mm).
The gain trim range of the MX8683 can accommodate even larger gaps if required.
Flex circuit MX8683
(2) E14 planar cores
Cross Section (drawing not to scale)
PCB top layer: (scale 1X) PCB bottom layer: (top view, 1X) Flex circuit: (component side, 1X)
Design alternativ es:
Multi-layer boards may be used with the MX8683 mounted directly on the board.
The use of an E-I core pair results in a lower profile than E-E however a thinner board must be used.
An example of a low-power circuit board with an added high-current copper strap:
MX8683
Copper stamping, thickness as required
MX8683 8 03/03/08
Drawing No. 0868309 www.claremicronix.com
MX8683 9 03/03/08
MX8683 IXYS
8 Lead DFN
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publication and reserves the right to make changes to specifications and product descriptions at any time without notice. Neither
circuit patent licenses nor indemnity are expressed or implied. Except as set forth in IXYS’ Standard Terms and Conditions of Sale,
IXYS Corporation assumes no liability whatsoever, and disclaims any expressed or implied warranty, relating to its products
including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any
intellectual property right.
Drawing No. 0868309 www.claremicronix.com
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MX8683 10 03/03/08
IXYS
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IXYS cannot assume responsibility for use of any circuitry other than circuitry
entirely embodied in this IXYS product. No circuit patent licenses nor indemnity
are expressed or implied. IXYS reserves the right to change the specification and
circuitry, without notice at any time. The products described in this document are
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applications where malfunction may result in direct physical harm, injury or death
to a person.
Specification: MX8683
©Copyright 2007, IXYS Corporation
All rights reserved. Printed in USA.
Drawing No. 0868309 www.claremicronix.com
