INPUTS
Current-Setting Inputs
The 4 input channels are transconductance-type inputs. This means the output current of the channel is
proportional to the current (not voltage) sourced into the input pin. That is why these pins are designated by the
letter “I” to indicate the current input nature of the pin. The read channel current-setting pin is “IR”, the Channel 2
current-setting pin is “I2” and so on. Using a transconductance-type input eliminates the high-impedance inputs
associated with a voltage input amplifier. The lower input impedances of the input nodes lowers the susceptibility
of the part to EMI/RFI. The Read Channel (IR) and Channel 3 (I3) and 4 (I4) current-setting inputs have a gain of
- The Channel 2 input (I2) has a current gain of 300. Sourcing one milliampere into the pins IR, I3 or I4, will
result in 150 mA at the output for each Channel, while 1 mA into I2 will result in 300 mA at the output for Channel
- These currents of 150 mA and 300 mA are the maximum allowable currents per channel. The total allowable
output current from all the channels operating together exceeds 500 mA.
How to calculate the input current ?
