LE87220KQC Zarlink, LE87220KQC Datasheet - Page 10

• Manufacturer Part Number: LE87220KQC
• Description: World Wide xDSL Line Driver 24-Pin QFN Tray
• Manufacturer: Zarlink

Specifications of LE87220KQC

• Package: 24QFN
• Transmission Media Type: Copper
• Power Supply Type: Analog
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.13 V
• Maximum Operating Supply Voltage: 3.46 V

DEVICE OPERATIONAL NOTES
Power Supplies
The Le87220 device is implemented in a high-voltage process that allows direct powering from the –42 V to –72 V battery supply
without the need for DC to DC converters. This saves significant power that would otherwise be wasted in the DC to DC converter.
The noise on (referenced to AGND) the battery supply (VBAT pin) and on the +3.3 V supply (VCC pin) should be below the limits
as shown in
Line Transformer
A step-down transformer is used to interface the Le87220 device with the TIP (A) and RING (B) line terminals. The transformer
injects the data signal onto the loop and provides dielectric isolation and impedance matching between the loop and the line driver.
The turn ratio of the transformer can be optimized to match the loop signal level to the driver output swing (see
Ratio, on page
Transformer Specifics
Figure 2
Z
SEC
represents a simplified transformer model in which the boxed block is an ideal transformer with an infinite bandwidth.
Secondary
Figure
11).
1, in order not to affect the data performance.
`
Figure 1. Allowed Noise on Power Supply Pins (Referenced to AGND)
140
120
100
80
60
40
20
0
0
R
SEC
100
N : 1
200
Figure 2. Le87220 Transformer
300
VBAT
VCC
Zarlink Semiconductor Inc.
400
L
PRI
R
500
frequency kHz
PRI
10
600
L
700
LEAK
800
900
Primary
C
PRI
1000
1100
RING(B)
TIP(A)
1200
Z
INTR
Transformer Turns