Product manual

Cheetah 4LP FC Product Manual, Rev. A 47

9.6 Signal characteristics

This section describes the electrical signal characteristics of the input and output signal of the drive. Refer to

Table 15 on page 43 for signal type and signal name information.

9.6.1 TTL input characteristics

Table 19 provides the TTL input characteristics.

9.6.2 LED driver signals

Fault and Active LED signals are located in the FC-SCA connector (J1) and through the indicator connector

(J6). Refer to Table 20 for the output characteristics of the LED drive signals.

9.6.3 Differential PECL output

The serial PECL output signal voltage characteristics are provided in Table 21. The outputs are not AC coupled

in order to deliver maximum signal without rise and fall time degradation. You must AC couple the receiver to

isolate potentially different DC characteristics of the outputs and the receiver.

Figure 15 provides the data output valid eye diagram relative to the bit cell time.

Figure 15. Transmit eye diagram

Table 19: TTL input characteristics

State Voltage Current

High 2.4 < V

< 5.5V 0 < I

< ±100µA

Low -0.5V < V

< 0.4V 0 < I

< -3 mA

Table 20: LED drive signal

State Current drive available Output voltage

LED off, high 0 < I

< 100µA

LED on, low I

< -30 mA 0 < V

< 0.8V

Table 21: Differential PECL output characteristics

Description Parameter Notes

Serial output voltage swing 300 < V

out

< 650 mV Centered at 1.32V

941 ps

Vout (mv)

800 ps