ADA4320-1

Rev. 0 | Page 13 of 16

RAMP PIN FEATURE

OUTPUT TRANSFORMER

The RAMP pin (Pin 6) can be optionally used to control the

length of the burst on and off transients. By default, leaving the

RAMP pin unconnected results in a transient that is fully compliant

with DOCSIS 3.0. Adding capacitance to the RAMP pin slows

the dissipation even more.

Matching the 300 Ω differential output impedance to unbalanced

75 Ω requires a 4:1 impedance (2:1 turns) ratio transformer.

The transformer should have minimal insertion loss over the

5 MHz to 85 MHz band and have a maximum dc current rating

of at least 200 mA.

Characterization of the ADA4320-1 was performed using a

Coilcraft PWB-4-BL surface-mount wide-band RF transformer.

Alternate choices for the output transformer are the Toko

458PT-1565 and the Tyco Electronics (M/A-COM) ABACT0018.

GND

GND

VIN–

VIN+

GND

COMP

VOUT+

VOUT–

VOUT+

VOUT–

ADA4320-1

0.1µF

10µF

LPF

QPSK/QAM

BURST

MODULATOR

DAC

DIPLEXER

TO TUNER

OR SPLITTER

0.1µF

3-WIRE

(SPI-COMPATIBLE)

CONTROL

POWER-DOWN

CONTROL

TRANSMIT

ENABLE/DISABLE

CONTROL

+

5V

100pF

0.1µF

0.1µF

100nH

2:1*

UPSTREAM

DOWNSTREAM

F-CONNECTOR

*COILCRAFT PWB-4-BL

ALTERNATES: TOKO 458PT-1565

TYCO MABACT0018

1

8

13

20

Figure 24. Typical Application