UC1901
UC2901
UC3901
µ
µ
Note: Transformer Data: N1 = N2 = 20TAWG 26
Core = Ferroxcube 3E2A Ferrite, 0.5" O.D. toroid
Carrier Frequency = 1MHz
Figure 1. Transformer Coupled Open Loop Transfer Function
Figure 2. Oscillator Frequency
APPLICATION INFORMATION
Figure 3. Typical Driver Output Swing vs
Temperature
The error amplifier compensation terminal, Pin 12, is in- With the internal oscillator the squarewave will have a
tended as a source of feedback to the amplifier's invert- fixed 50% duty cycle. If the internal oscillator is disabled
ing input at Pin 11. For most applications, a series DC by connecting Pin 1, C , to V then the frequency and
R
IN
blocking capacitor should be part of the feedback net- duty cycle of the output will be determined by the input
work. The amplifier is internally compensated for unity clock waveform at Pin 2. If the oscillator remains disabled
feedback.
and there is not clock input at Pin 2, there will be a linear
12dB of signal gain to one or the other of the driver out-
puts depending on the DC state of Pin 2.
The waveform at the driver outputs is a squarewave with
an amplitude that is proportional to the error amplifier in-
put signal. There is a fixed 12dB of gain from the error The driver outputs are emitter followers which will source
amplifier compensation pin to the modulator driver out- a minimum of 15mA of current. The sink current, inter-
puts. The frequency of the output waveform is controlled
by either the internal oscillator or an external clock signal.
nally limited at 700µA, can be increased by adding resis-
tors to ground at the driver outputs.
4
TI [ TEXAS INSTRUMENTS ]
