300 SERIES USER GUIDE
16
Normal Output
This is a +5V CMOS output signal in series with an internal 1.87K resistor.
It will be HI (+5V) when the Normal LED is on, and LO (ground) when the Normal
LED is off. It can drive an external low-current LED, or CMOS logic compatible inputs
to user equipment.
Reset Input
A +5V CMOS logic input which is normally pulled-up to +5V by an internal 100K
resistor. Ground this signal momentarily to reset a fault condition caused by overtemp, or
output short-circuit.
Do not ground this input continuously, as this could cause overloading of the output
stage of the amplifier. If you want to shutdown the amplifier, use the Enable input.
Current Limit
On the basic amplifier, component R8 on header J17 controls the maximum current
delivered by the amplifier. A value of 10K ohms is standard and will let the amplifier
deliver the maximum rated peak current. Substitute smaller values to reduce the limiting
current.
The MB4 and Eurocard come with potentiometers that lets you adjust the maximum
current to any set value from 0, to the maximum rated peak current.
In either case, whenever the current-limit is greater than the continuous current rating of
the amplifier, it will fold-back to the continuous current rating after 1 second for unipolar
currents, or 2 seconds for bipolar currents.
Output Voltage Swing
300 series amplifiers use MOSFET transistors in the output stages. These have no
inherent 'saturation' voltage like bipolar transistors. Instead, they look like low value
resistors in series with the power supply. The table below lists the on-resistance and
output voltage-drop for the various amplifiers.
Note that output voltage swing is relative to the instantaneous supply voltage. Therefore,
if you have an application that requires a particular voltage swing, you must add to this
the output voltage-drop, power supply ripple voltage, and use this as your low-line power
supply operating voltage.
Amplifier Rout Vsat
303,303B 0.26 3.12
306,306B 0.13 3.25
306A,306AB 0.13 3.9
312 0.60 5.4
Table 7
Rout is the amplifier output resistance.
Vsat is the voltage-drop (also called saturation voltage) across the amplifier at peak
current.
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