TDA4700 Datasheet, PDF (8/21 Pages) Siemens Semiconductor Group – Control IC for Single-Ended and Push-Pull Switched-Mode Power Supplies SMPS

TDA 4700
TDA 4718
Comparator K7
K7 serves to recognize overcurrents. This is the reason why both inputs of the op amp
have been brought out. Turning on is resumed after error recovery at the beginning of
the next half period but without using the soft start.
K7 has a common-mode range covers 0 V and + 4 V. The delay time between
occurrence of an error and disabling of the outputs is only 250 ns.
Symmetry (TDA 4700; A)
In push-pull converters, a saturation of the transformer core must be prevented. The
degree of saturation of the transformer can be determined with an external circuit, thus
the active periods of the outputs can be decreased unsymmetrically at the symmetry
inputs.
Outputs
Both outputs are transistors with open collectors and operate in a push-pull
arrangement. They are active low. The time in which only one of the two outputs is
conductive can be varied infinitely. The length of the falling edge at VCO is equal to the
minimum time during which both outputs are disabled simultaneously. The minimum
L voltage is 0.7 V.
Reference Voltage
The reference voltage source is a highly constant source with regard to its temperature
behavior. It can be utilized in the external wiring of the op amp, the error comparators,
the ramp generator, or other external components.
Semiconductor Group
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