Data Sheet

ADCA5191

APPLICATIONS INFORMATION

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Rev. 0 | 19 of 24

DOWNSTREAM APPLICATIONS CIRCUIT

The schematic in Figure 39 is recommended for downstream cable

system applications from 45 MHz to 1800 MHz. Recommended

values for all components are in the BOM listed in Table 10. T1

is an RF transformer configured to transform the single-ended 75

Ω RF input to a differential signal that drives the 37.5 Ω inputs of

the ADCA5191 (RFIN and RFIP). The voltage at Pin 1 of E2 is

a series of components (R6, R4, and E1) and supplies the dc

reference on the RF input side of T1. C6 stabilizes this reference

and serves as the ac ground for the RF input signal.

T2 is an RF transformer configured to transform the differential 37.5

Ω outputs (RFON and RFOP) to a single-ended 75 Ω RF output.

The C2, C3, C5, C7, C8, C13, C14, C21, L8, L9, L10, and L11

components are intended for impedance matching, and these com-

ponents must be optimized to match the RF input source and RF

output load. Capacitor C4 blocks the dc voltage of the RF input

source. Capacitor C27 and Capacitor C28 are for blocking the dc

voltage at the RFOP (Pin 22 and Pin 23) and RFON (Pin 18 and

Pin 19) output pins. Inductors L2 and L3 are RF chokes connected

to the filtered VDD supply voltage. The passive networks connected

to the BIASA and BIASB pins (Pin 11 and Pin 30) are also part

of the supply and biasing required for the ADCA5191 and are

discussed in detail in the Supply Voltage and Bias Current section.

Figure 39. Suggested Downstream Cable TV (CATV) Application Circuit