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PDF MX844 Data sheet ( Hoja de datos )
| Número de pieza | MX844 | |
| Descripción | MULTI-CHANNEL POWER & TEMP SENSOR | |
| Fabricantes | IXYS Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MX844 (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
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IXYS
MX844www.DataSheet4U.com
12 BIT, MULTI-CHANNEL POWER & TEMP
SENSOR FOR MONITOR & CONTROL SYSTEMS
Features:
• Wide Input Supply Range: 4.5V to 40V
• Programmable gain differential amplifier
(±10mV, ±25mV, ±50mV, ±250mV ranges)
• 4 channel differential input multiplexer
(3 input channels plus ground)
• Integrated 12-bit ADC
• Serial data output (SDO) with data ready pin
• Fine calibration of Full Scale Range (FSR)
using VTRIM pin
• Bi-directional Current Sense
• Internal temperature sensor with 0.2°C
resolution
• Compatible with 3.3V and 5V
Microcontrollers
• Operating Temperature Range: -40°C to
85°C
• 5mm x 5mm, QFN-28 RoHS Package
Ordering Information
Part No. Description
MX844R QFN-28 Tube
MX844RTR QFN-28 Tape & Reel
Qty
73
2500
Description:
The MX844 is a fully integrated subsystem that
measures temperature plus differential current and
voltage. An internal temperature sensor measures
ambient temperature with 2.5°C accuracy. Current
and voltage measurements are made differentially
through a four input multiplexer connected to a
programmable gain fully differential sense amplifier.
The differential sense amplifier is optimized to
measure very small positive or negative voltages
near ground for low side bi-directional sensing. A
dual slope ADC converts the temperature sensor or
sense amplifier outputs to a 12-bit digital word that
includes 3 ½ digits plus sign. The input multiplexer
channel and programmable gain amplifier range may
be changed between ADC conversions. An on-chip
voltage regulator enables the MX844 to operate over
a wide input voltage range of 4.5 to 40 volts.
Controller interrupt or over-voltage/over-current
signals may be generated by a pair of 12-bit digital
comparators configured as a window comparator or
simple threshold detection function. The serial port
supports standard 4-wire synchronous serial data, or
asynchronous serial “talk-only” data, and is
compatible with most 3.3V and 5V microcontrollers.
DRV
RIN
VIN
IN1P
IN2P
IN3P
IN1N
IN2N
IN3N
GND
VTRIM
VCC
Regulator
BUF CAZ CINT IZ
Registers
ADC
Control
Serial
I/O
Te m p e ra tu re
Sensor
Divider
M1
SDI
SDO
SCK
CS
AOUT
DRDY
CMP
X1
X2
SYNC
Typical Application:
Batt
T
Charging
system
Load
MX844
IN
IN
IN
uP
Rectifier
Load
MX844
IN
IN
93C46
eeprom
uP
Battery charge/discharge current, voltage, temperature
MX844
Drawing No. 084423
Isolated voltage, current, and temperature sensing
1 08/25/06
www.claremicronix.com
1 page  
MX844
IXYSwww.DataSheet4U.com
Analog/Digital Converter
Selection of the input channel and the full scale range is accomplished by writing 5 bits in the control
register. An additional 3 bits in the control register in combination with the M1 pin setup the internal clock
dividers. The ADC is a bipolar-input dual slope type with clock period tAD equal to a multiple of the clock
period at pin X1 (tClock). The ADC conversion time consists of 1024 * tAD of auto-zero, 1024 * tAD of
input integration, and 2048 * tAD of reference integration. The result of the analog to digital conversion
can be read using the serial I/O port and is also transmitted on pin AOUT in an asynchronous serial
format. The DRDY pin transitions low at the end of the reference integration period to indicate that data is
stable and may be read through the synchronous serial I/O. The data becomes not valid when DRDY
returns high. The status of DRDY is also available in bit 7 of the ADC_1 register.
The SYNC pin is connected to GND to enable free-running ADC conversions. Alternatively, if SYNC
transitions high, the ADC is immediately driven to the start of the auto-zero time. When SYNC is returned
to a logic low, the next rising edge at pin X2 will start the ADC timing.
The input channel and full scale range may be changed in between ADC conversions, however it is
recommended that such commands be written into the MX844 as soon as possible after pin DRDY
transitions low. This allows the maximum settling time prior to the next ADC conversion.
ADC clock # 0
1023 1024
2047 2048
4095 0
1023 1024
2047 2048
SYNC
auto-zero
input integrate
reference integrate
next auto-zero
DRDY (active low)
CMP (active low)
AOUT
6 data bits
6 data bits
DRDY and CMP cleared if ADC_2 register is read
CMP is the digital compare output that is described later. AOUT is the asynchronous serial output of the
ADC.
The ADC output code is offset-binary. An example of the coding is shown here for the +/-50mV range and
the corresponding unipolar range of 0 to 100mV:
Bipolar input
50mV
0 + 1/2 LSB
0 - 1/2 LSB
-50mV
Unipolar input
100mV
50mV + 1/2 LSB
50mV - 1/2 LSB
0
Binary Output (D11:D0)
111111111111
100000000000
011111111111
000000000000
Hexadecimal
FFF
800
7FF
000
Two external components, Rin and Cint, should be chosen such that the value of Cint in pF is 4 to 7 * tAD
and the time constant of Rint * Cint is 300 to 450 * tAD. The value of Rint should be between 47K and
220K ohm. For example, for t(AD) = 1.6 uS, a set of suitable values would be 56K ohm and 10nF (RC =
560uS, ratio = 350). The value of the auto-zero capacitor Caz is typically equal to Cint.
VTRIM is either a no-connect pin or can be used to fine
trim the ADC full scale by +/- 1%. The following circuit
is recommended if fine trimming is desired:
VCC
20K
1K VTRIM
GND
MX844
Drawing No. 084423
5 08/25/06
www.claremicronix.com
5 Page 
MX844
IXYSwww.DataSheet4U.com
APPLICATION EXAMPLE - POWER MONITOR
This design example illustrates the application of the MX844 as an AC line power monitor.
In this design the MX844 operates as a serial bus master, reading instructions from an external serial
EEPROM.
Following application of power, the first 16-bit word read from the EEPROM is 0x8200 (using "C" notation
to indicate a hexadecimal number) which in conjunction with the connection of terminal M1 to VCC,
causes the MX844 to set it's internal dividers for 488 A/D samples per second and an asynchronous baud
rate of 38.4 Kbaud when using an 8 MHz clock. The first measurement is made from input channel IN1
on the +/- 50 mV scale. For the power meter this is a measurement of the AC line current flowing through
sense resistor R1. A value of 0.002 Ohm for R1 results in a +/- 25A current scale.
The second instruction is 0x83A0, which results in a measurement from input channel IN2 on the +/- 250
mV scale. For the power meter this is a measurement of the AC line voltage through the voltage
attenuator consisting of resistors R2, R3, and R4 which provide a full scale of +/- 407 V.
The MX844 cycles through the first eight addresses of the EEPROM. Therefore the first two instruction
codes are repeated three more times in order to continuously alternate between AC line voltage and
current measurements.
This is how the EEPROM contents would appear in a typical programmer buffer editor:
00 82 A0 83 00 82 A0 83 00 82 A0 83 00 82 A0 83
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Note that the 16-bit word is broken up into two bytes with the least significant byte first.
The power monitor is powered directly off the line using resistors R14 - R20, diodes D1 and D2, and
capacitor C1 to produce an unregulated DC voltage for the MX844.
Opto-isolator U3 provides isolation between the AC power line and the computer serial port. Dual
transistors Q1 and Q2 and related circuitry amplify the photodiode signal into the required RS-232 signal
for the computer serial port. Power for the photodiode amplifier is very small and is supplied by the serial
port DTR and RTS terminals.
By analyzing the data stream from the MX844 the computer software program can determine the RMS
line voltage, the RMS line current, the RMS power consumed, and the power factor of the load.
Each digitized sample is transmitted to the computer as two 8-bit "characters" in asynchronous RS-232
format. Embedded in the two characters are the 12 bits of data and a 3-bit EEPROM address.
MX844
Drawing No. 084423
11 08/25/06
www.claremicronix.com
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet MX844.PDF ] | |
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