Datasheet

+3V to +5V, 2500V
RMS
Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
product of 9.5V-µs. The commercially available trans-
formers for the MAX845 listed in Table 5 meet that
requirement. In most cases, use half of the center-tapped
primary winding with the MAX3535E and leave the other
end of the primary floating. Most of the transformers in
Table 5 are 1:1:1 or 1:1:1:1 turns ratio.
For +3.3V operation (+3.6V maximum) the required pri-
mary ET product is 6.2V-µs. All of the previously men-
tioned transformers meet this requirement. Table 6 lists
some other transformers with step-up turns ratios
specifically tailored for +3.3V operation. Most of the
transformers in Table 6 are 1:1:1.3:1.3.
By using a HALO TGM-010 or Midcom 95061 trans-
former, it becomes possible to build a complete isolated
RS-485/RS-422 transceiver with a maximum thickness
less than 0.1in. To minimize power consumption, select
the turns ratio of the transformer to produce the minimum
DC voltage required at V
CC2
(+3.13V) under worst-case,
high-temperature, low-V
CC1
, and full-load conditions. For
light loads on the isolated side, ensure that the voltage at
V
CC2
does not exceed +7.5V. For example, the CTX01-
14659 transformer results in 85mA (typ) V
CC1
supply cur-
rent with full load on the RS-485 driver. Using a TGM250
1:1:1 transformer lowers the V
CC1
supply current to 65mA
(typ), while maintaining good margin on the V
CC2
supply.
A slight step-down transformer can result in extra power
savings in some situations. A custom wound sample
transformer with 23 primary turns and 20:20 secondary
turns on a Ferronics 11-050B core operates well with a
V
CC1
supply current of 51mA (typ).
Table 4. Transformers for the MXL1535E/MAX3535E
MANUFACTURER PART NUMBER ISOLATION VOLTAGE (1s) PHONE NUMBER
Cooper Electronic Technologies, Inc. CTX01-14659 500V 561-241-7876
Cooper Electronic Technologies, Inc. CTX01-14608 3750V
RMS
561-241-7876
EPCOS AG (Germany)
(USA)
B78304-A1477-A3 500V
0 89-626-2-80-00
800-888-7724
Midcom, Inc. 31160R 1250V 605-886-4385
Pulse FEE (France) P1597 500V 33-3-85-35-04-04
Sumida Corporation (Japan) S-167-5779 100V 03-3667-3320
Transpower Technologies, Inc. TTI7780-SM 500V 775-852-0145
Table 5. Transformers for MAX3535E at +5V
MANUFACTURER
PART
NUMBER
ISOLATION
VOLTAGE (1s)
PHONE
NUMBER
WEBSITE
TGM-010 500V
RMS
TGM-250 2000V
RMS
TGM-350 3000V
RMS
HALO Electronics, Inc.
TGM-450 4500V
RMS
650-903-3800 www.haloelectronics.com/6pin.html
BH Electronics, Inc. 500-1749 3750V
RMS
952-894-9590
www.bhelectronics.com/PDFs/DC-
DCConverterTransformers.pdf
Coilcraft, Inc. U6982-C 1500V
RMS
800-322-2645
44-1236-730595
www.coilcraft.com/minitrans.cfm
7825355
1500V
Newport/C&D Technologies
7625335 4000V
520-295-4300 www.dc-dc.com/products/productline.asp?ED=9
Midcom, Inc. 95061 1250V 605-886-4385 www.midcom-inc.com
PCA Electronics, Inc. EPC3115S-5 700V DC 818-894-5791 www.pca.com/Datasheets/EPC3117S-X.pdf
Rhom b us Ind ustr i es, Inc. T-1110 1800V
RMS
714-898-0960 www.rhombus-ind.com/pt-cat/maxim.pdf
Premier Magnetics, Inc. PM-SM15 1500V
RMS
949-452-0511 www.premiermag.com/pdf/pmsm15.pdf
MAX3535E/MXL1535E
Maxim Integrated
21