MAX1366ECM Maxim Integrated, MAX1366ECM Datasheet - Page 30

• Manufacturer Part Number: MAX1366ECM
• Description: LED Display Drivers
• Manufacturer: Maxim Integrated

Microcontroller-Interface, 4.5-/3.5-Digit Panel
Meters with 4–20mA Output
In either internal or external reference operation,
bypass REF_DAC with a 0.1µF capacitor to GND.
Choose a reference with output impedance (load regu-
lation equivalent) of 100mΩ or less, such as the
MAX6126. For best performance, use an external
source from the ADC and DAC.
The MAX1366/MAX1368 offer on-chip offset calibration.
The device offset calibrates during every conversion
when the OFFSET_CAL1 bit is zero in the control regis-
ter. Enhanced offset calibration is only needed in the
MAX1366 when the RANGE bit = 1. It is performed on
demand by setting the OFFSET_CAL2 bit to 1.
Enhanced offset calibration is a more accurate calibra-
tion method that is needed in the case of the ±200mV
range and 4.5-digit resolution. The MAX1366 performs
enhanced calibration on demand by setting the
OFFSET_CAL2 bit to 1.
The MAX1366/MAX1368 feature independent power-down
control of the analog and digital LED driver’s circuitry.
Writing a 1 to the PD_DIG and PD_ANA bits in the con-
trol word, powers down the analog and digital circuitry,
reducing the supply current to 268µA (typ). PD_DIG
powers down the digital filter, while PD_ANA powers
down the analog modulator and ADC input buffers.
Writing a zero to the ENABLE bit in the control word
powers down the LED drivers.
The MAX1366/MAX1368 feature peak-detection circuitry.
When activated (PEAK bit = 1), the devices display
only the highest voltage measured to the LED.
The MAX1366/MAX1368 feature data-hold circuitry.
When activated (HOLD bit = 1), the device holds the
current reading on the LED.
The MAX1366/MAX1368 feature a low-battery detection
input. When the voltage at LOWBATT drops below
2.048V (typ), LOWBATT in the status register goes high.
Connect the differential inputs of the MAX1366/
MAX1368 to the bridge network of the strain gauge. In
Figure
network and the MAX1366/MAX1368, along with the
reference voltage. The MAX1366/MAX1368 handle an
analog input voltage range of ±200mV and ±2V full
scale. The analog/reference inputs of the parts allow
30
______________________________________________________________________________________
14, the analog supply voltage powers the bridge
Enhanced Offset Calibration
Strain-Gauge Measurement
Power-Down Modes
Offset Calibration
Low Battery
Peak
Hold
the analog input range to have an absolute value of
anywhere between -2.2V and +2.2V.
Figure 15
the MAX1366/MAX1368. In this application, the
MAX1366/MAX1368 take advantage of the on-chip input
buffers that allow large source impedances on the front
end. The decoupling capacitors reduce noise pickup
from the thermocouple leads. To place the differential
voltage from the thermocouple at a suitable common-
mode voltage, the AIN- input of the MAX1366/MAX1368
is biased to GND. Use an external temperature sensor,
such as the DS75, and a microcontroller to perform cold-
junction temperature compensation.
Figures 16–19
MAX1366/MAX1368. The output data is stored in the
ADC data register in two’s complement.
The transfer function for the MAX1366 with AIN+ - AIN-
≥ 0 and RANGE = GND is:
The transfer function for the MAX1366 with AIN+ - AIN-
< 0 and RANGE = GND is:
The transfer function for the MAX1368 with AIN+ - AIN-
≥ 0 and RANGE = GND is:
The transfer function for the MAX1368 with AIN+ - AIN-
< 0 and RANGE = GND is:
The transfer function for the MAX1366 with AIN+ - AIN-
≥ 0 and RANGE = DV
( )
( )
( )
( )
( )
4
2
3
1
5
COUNT
COUNT
COUNT
COUNT
COUNT
shows a connection from a thermocouple to
=
=
=
=
=
1 024
1 024
1 024
1 024
1 024
.
show the transfer functions of the
.
.
.
.
Thermocouple Measurement
DD















V
V
V
V
V
V
V
V
V
V
REF
REF
REF
REF
AIN
REF
AIN
AIN
AIN
is:
AIN
+ −
+ −
+ −
+ −
+ −
+ −
+ −
+ −
+ −
+ −
ADC Transfer Functions
Transfer Functions
V
V
V
V
V
V
V
V
V
V
AIN
REF
AIN
REF
AIN
REF
AIN
REF
AIN
REF
−
−
−
−
−
−
−
−
−
−
x
x
x
x
x
20 000
2000
2000
20 000
20 000
,
,
,




 +








 +

1
x
1
10