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LE87251NQCT

P1-P3P4-P6P7-P9P10-P12P13-P14
Le87251
Data Sheet
7
Zarlink Semiconductor Inc.
--------------
L
L
The output impedance and the voltage gain of the circuit in Figure 5 are shown in the following equations.
Z
OUT
= K
•
R
BM
-
V
-----
O
---
=
-----------------
R
---
D
----
( P
---
2
--
)
---------------
---
---
V
IN
2( RD ( G ) – RD ( P1 ) )
where
ZOUT is the output impedance.
K =
--------------
1
---------------
1 –
-
R
---
D
---
( P
--
1
-
)
-----
---
RD( G )
And the resistor dividers are defined as following
RD( P1 ) =
--------
RP1
----
-
-
-
RP1 + RP2
RD( P2 ) =
---------
R
-----
P
---
2
---------
-
-
-
RP1 + RP2
RD( G ) =
--------
R
----
G
----------
RG + R F
And VO/VIN represents the voltage gain.
R
G
R
F
V
IN
R
BM
Z
V
O
R
L
Figure 4 - Passive Termination
Technique
R
G
R
F
V
IN
R
P1
R
P2
R
BM
Z
V
O
R
L
Figure 5 - Active Termination Technique
Le87251
Data Sheet
8
Zarlink Semiconductor Inc.
Passive Termination Active Termination
16.5 V
P-P
into a 100 Ω line 16.5 V
P-P
into a 100 Ω line
V
OUT DRIVER
= V
RBM
+ V
RLOAD
V
OUT DRIVER
= V
RBM
+ V
RLOAD
RBM = R
LOAD
RBM = R
LOAD
/5
V
RBM
= V
RLOAD
V
RBM
= V
RLOAD
/5
V
OUT DRIVER
= 33.52 V
V
OUT DRIVER
= 20.11 V
V
SUPPLY
= 37.52 V V
SUPPLY
= 24.11 V
I
OUT
= 31.6 mA I
OUT
= 31.6 mA
P
OUT DRIVER
= V
SUPPLY
* I
OUT
= 1.185 W (plus
quiescent power)
P
OUT DRIVER
= V
SUPPLY
* I
OUT
= 0.714 W
(plus quiescent power)
Table 2 - Passive and Active Termination Comparison
2.3 Line Driver Protection
High voltage transients such as lightning can appear on the telephone lines. Transient protection devices should be
used to absorb the transient energy and clamp the transient voltages. However, large transient voltages can still
couple to the primary side of the transformer. As shown in Reference Circuit 2, the outputs of the Le87251
incorporate on-chip circuitry that clamps the output voltage to no more than a diode drop beyond either rail. No
external diodes immediately at the output of the amplifiers are required. As shown in Figure 6, the series output
termination resistors limit the current going into the line driver and internal clamps, thus these termination resistors
should be specified at 0.5 W. The actual protection scheme may
vary depending on the type of data transformer
used and the line protection components used in the front of the data transformer.
V
IN
+
R
F
R
BM
0.5W
2R
G
R
F
Subscriber
Line
V
IN
-
R
BM
0.5W
Figure 6 - Line Driver Protection
A large DC voltage can develop between the line driver outputs during system turn-on when the AFE has not been
reset or when the line driver is disabled. Figure 6 shows an AC coupling capacitor between the two line driver
outputs. This AC coupling capacitor prevents large DC current from flowing from one output of the line driver to
another.
Le87251
Data Sheet
9
Zarlink Semiconductor Inc.
3.0 Absolute Maximum Ratings
Stresses above the values listed under Absolute Maximum Ratings can cause permanent device failure.
Functionality at or above these limits is not implied. Exposure to absolute maximum ratings for extended periods
can affect device reliability.
Storage Temperature −65 ≤ T
A
≤ +150°C
Operating Ambient Temperature −40 ≤ T
A
≤ +85°C
Operating Junction Temperature
(See Notes 1 and 2)
−40 ≤ T
A
≤ +150°C
VS+ to VS- Supply Voltage
−0.3 V to 30 V
VS+ with respect to GND
−0.3 V to 30 V
VS- with respect to GND
−30 V to +0.3 V
Driver inputs VINA/B/C/D VS- to VS+
Control inputs ENAB/ENCD with respect to GND
−0.3 V to 6 V
Maximum current on any input 10 mA
Maximum current at amplifier output (DC continuous) 100 mA
ESD Immunity (Human Body Model) JESD22 Class 2 compliant
ESD Immunity (Charge Device Model) JESD22 Class IV compliant
Note: Continuous operation above 145°C junction temperature may degrade device
reliability.
3.1 Thermal Resistance
The thermal performance of a thermally enhanced package is assured through optimized printed circuit
board layout. Specified performance requires that the exposed thermal pad be soldered to an equally sized
exposed copper surface, which, in turn, conducts heat through multiple vias to larger internal copper
planes.Please refer to the QFN Package application note, available from http://www.zarlink.com
, for layout and
heat sinking guidelines.
3.2 Package Assembly
The green package devices are assembled with enhanced, environmental compatible lead-free, halogen-free, and
antimony-free materials. The leads possess a matte-tin plating which is compatible with conventional board
assembly processes or newer lead-free board assembly processes.
Refer to IPC/JEDEC J-Std-020 Table 4-2 for recommended peak soldering temperature and Table 5-2 for the
recommended solder reflow temperature profile
.
P1-P3P4-P6P7-P9P10-P12P13-P14

LE87251NQCT

Mfr. #:
Buy LE87251NQCT
Manufacturer:
Microchip / Microsemi
Description:
Buffers & Line Drivers 2CH ADSL2+, 12V Line Driver, QFN16, T&R
Lifecycle:
New from this manufacturer.
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