Owner's manual
Bipolar Mode
Set EN_BPM high to engage bipolar operation. In bipo-
lar mode, the current output at 4–20OUT (4–20mA or
0 to 16mA) maps the analog input voltage (±2V or
±200mV). In bipolar mode, a 0V analog input maps to
midscale (12mA). See Table 5 for current output (see
Figures 12 and 13).
5.2V Linear Regulator with Compensation
The MAX1365/MAX1367 feature a 5.2V linear regulator.
The 5.2V regulator consists of an op amp and connec-
tions to an external depletion-mode FET. The 5.2V regu-
lator regulates the loop voltage that powers the
voltage-to-current converter and the rest of the trans-
mitter circuitry. The regulator output voltage is available
at REG_VDD and is given by the equation:
V
REG_VDD
= 2.54 x V
REF+
The FET breakdown and saturation voltages determine
the usable range of loop voltages (V
EXT
). The external
FET parameters such as V
GS
(off), I
DSS
, and transcon-
ductance must be chosen so that the op amp output on
the REG_FORCE pin can control the FET operating
point while swinging in the range from VREG_AMP to
REG_VDD. See the Selecting Depletion-Mode FET sec-
tion in the Applications Information section.
Connect a 0.1µF capacitor between CMP and
REG_FORCE to ensure stable operation of the regulator.
Applications Information
Power-On Reset
At power-on, the digital filter and modulator circuits
reset. The MAX1365 allows 6s for the reference to sta-
bilize before performing enhanced offset calibration.
MAX1365/MAX1367
Stand-Alone, 4.5-/3.5-Digit Panel Meters
with 4–20mA Output
______________________________________________________________________________________ 15
CURRENT OUTPUT (mA)
ANALOG INPUT
UNIPOLAR MODE
(EN_I = LOW)
UNIPOLAR MODE
(EN_I = HIGH)
BIPOLAR MODE
(EN_I = LOW)
BIPOLAR MODE
(EN_I = HIGH)
Negative Full Scale 0 4 0 4
0V 0 4 8 12
Positive Full Scale 16 20 16 20
Table 5. Current Output Table
MAX1365
MAX1367
AV
DD
DV
DD
10µF
10µF
0.1µF
0.1µF
0.1µF
0.1µF
ANALOG SUPPLY
FERRITE
BEAD
R
REF
R
R
ACTIVE
GAUGE
DUMMY
GAUGE
REF+
REF-
NEGV
AIN+
AIN-
4-20OUT
4–20mA/0 TO 16mA
CURRENT-LOOP
OUTPUT
GND
0.1µF
0.1µF
Figure 6. Strain-Gauge Application with the MAX1365/MAX1367