DC1747A-B Linear Technology, DC1747A-B Datasheet - Page 11

• Manufacturer Part Number: DC1747A-B
• Description: EVALUATION KIT LOW EM1 LTM2882-5
• Manufacturer: Linear Technology
• Series: µModuler

Specifications of DC1747A-B

• Main Purpose: Interface, Transceiver RS-232
• Embedded: No
• Utilized Ic / Part: LTM2882
• Primary Attributes: 5V Supply, Dual, Isolated, Transceiver + Power
• Kit Contents: Board, Datasheet
• Tool / Board Applications: Interface-Backplane, PCI, PCI Express, RS-XXX, Digital & Opto Isolator
• Mcu Supported Families: LTM2882
• Development Tool Type: Hardware - Eval/Demo Board
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Secondary Attributes: -

applicaTions inForMaTion
Overview
The LTM2882 µModule transceiver provides a galvani-
cally-isolated robust RS232 interface, powered by an
integrated, regulated DC/DC converter, complete with
decoupling capacitors. The LTM2882 is ideal for use in
networks where grounds can take on different voltages.
Isolation in the LTM2882 blocks high voltage differences,
eliminates ground loops and is extremely tolerant of com-
mon mode transients between grounds. Error-free opera-
tion is maintained through common mode events greater
than 30kV/μs providing excellent noise isolation.
µModule Technology
The LTM2882 utilizes isolator µModule technology to
translate signals and power across an isolation barrier.
Signals on either side of the barrier are encoded into
pulses and translated across the isolation boundary using
coreless transformers formed in the µModule substrate.
This system, complete with data refresh, error checking,
safe shutdown on fail, and extremely high common mode
immunity, provides a robust solution for bidirectional signal
isolation. The µModule technology provides the means
to combine the isolated signaling with our advanced dual
RS232 transceiver and powerful isolated DC/DC converter
in one small package.
DC/DC Converter
The LTM2882 contains a fully integrated isolated DC/DC
converter, including the transformer, so that no external
components are necessary. The logic side contains a full-
bridge driver, running at about 2MHz, and is AC-coupled
to a single transformer primary. A series DC blocking
capacitor prevents transformer saturation due to driver
duty cycle imbalance. The transformer scales the primary
voltage, and is rectified by a full-wave voltage doubler.
This topology eliminates transformer saturation caused
by secondary imbalances.
The DC/DC converter is connected to a low dropout regulator
(LDO) to provide a regulated low noise 5V output, V
An integrated boost converter generates a 7V V
and a charge pumped –6.3V V
the output stage of the RS232 drivers and are regulated to
levels that guarantee greater than ±5V output swing.
EE
supply. V
DD
and V
DD
EE
supply
power
CC2
.
The internal power solution is sufficient to support the
transceiver interface at its maximum specified load and
data rate, and has the capacity to provide additional 5V
power on the isolated side V
V
capacitors.
V
A separate logic supply pin V
face with any logic signal from 1.62V to 5.5V as shown in
Figure 5. Simply connect the desired logic supply to V
There is no interdependency between V
may simultaneously operate at any voltage within their
specified operating ranges and sequence in any order. V
is bypassed internally by a 2.2µF capacitor.
Hot Plugging Safely
Caution must be exercised in applications where power
is plugged into the LTM2882’s power supplies, V
due to the integrated ceramic decoupling capacitors. The
parasitic cable inductance along with the high Q char-
acteristics of ceramic capacitors can cause substantial
ringing which could exceed the maximum voltage ratings
and damage the LTM2882. Refer to Linear Technology Ap-
plication Note 88, entitled “Ceramic Input Capacitors Can
Cause Overvoltage Transients” for a detailed discussion
and mitigation of this phenomenon.
CC2
L
Logic Supply
are each bypassed internally with 2.2µF ceramic
ANY VOLTAGE FROM
1.62V TO 5.5V
EXTERNAL
DEVICE
Figure 5. V
3.0V TO 3.6V LTM2882-3
4.5V TO 5.5V LTM2882-5
CC
ON
DIN
T1IN
R1OUT
T2IN
R2OUT
V
L
and V
GND
V
CC
L
CC2
L
allows the LTM2882 to inter-
Are Independent
and GND2 pins. V
LTM2882
GND2
LTM2882
CC
T1OUT
T2OUT
DOUT
V
R1IN
R2IN
and V
2882 F05
CC2
DE
CC
11
L
CC
; they
or V
2882fb
and
L
L
.
L
,