The SY88903V limiting post amplifier with its high gain and wide bandwidth is ideal for use as a post amplifier in fiber-optic receivers with data rates up to 1.25Gb/s. Signals as small as 5mVp-p can be amplified to drive devices with PECL inputs. The SY88903V generates a chatter-free Loss of Signal (LOS) open collector TTL output.
The SY88903V incorporates a programmable level detect function to identify when the input signal has been lost. This information can be fed back to the /EN input of the device to maintain stability under loss of signal condition. The sensitivity of the level detection can be adjusted using LOSLVL. The LOSLVL voltage can be set by connecting a resistor divider between VCC and VREF as shown in Figure 3. Figure 4 and 5 show the relationship between input level sensitivity and the voltage set on LOSLVL.
The LOS output is a TTL open collector output that requires a pull-up resistor for proper operation.