TDA4718A Infineon Technologies, TDA4718A Datasheet - Page 5

• Manufacturer Part Number: TDA4718A
• Manufacturer: Infineon Technologies

Specifications of TDA4718A

• Operating Temperature (max): 85C
• Operating Temperature (min): -25C
• Pin Count: 18
• Mounting: Through Hole
• Package Type: PDIP
• Screening Level: Commercial
• Lead Free Status / Rohs Status: Supplier Unconfirmed

TDA 4718 A
Comparator K3
C
Comparator K3 limits the voltage at capacitance
(and also at K2) to a maximum
soft start
of + 5 V. The voltage at the ramp generator output may, however rise to 5.5 V. With a
corresponding slope of the rising ramp generator edge, the duty cycle can be limited to
a desired maximum value.
Comparator K4
The comparator has its switching threshold at 1.5 V and sets the error flipflop with its
output if the voltage at capacitance C
is below 1.5 V. However, the error flipflop
soft start
accepts the set signal only if no reset pulse (error) is applied. In this way the outputs
cannot be turned on again as long as an error signal is present.
Soft Start
The lower one of the two voltages at the plus inputs of K2 is a measure for the duty cycle
C
at the output. At the instant of turning on the component, the voltage at capacitor
soft start
equals 0 V. As long as no error is present, this capacitor is charged with a current of 6 A
C
to the maximum value of 5 V. In case of an error,
is discharged with a current of
soft start
2 A. A set signal is pending at the error flipflop below a charge of 1.5 V and the outputs
are enabled if no reset signal is pending simultaneously. As the minimum ramp
generator voltage, however, is 1.8 V, the duty cycle at the outputs is actually increased
slowly and continuously not before the voltage at
C
exceeds 1.8 V.
soft start
Error Flipflop
Error signals, which are led to input R of the error flipflop cause an immediate disabling
of the outputs, and after the error has been eliminated, cause the component to switch
on again by the soft start.
V
Comparator K5, K6, K8,
Overcurrent Load
REF
These are error detectors which cause immediate disabling of the outputs via the error
flipflop when an error occurs. After elimination of the error, the component switches on
again using the soft start. The output of K5 can be fed back to the input. This causes the
IC output stage to remain disabled even after elimination of the overvoltage. However, it
requires high-ohmic overvoltage coupling.
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.
Semiconductor Group
5