KA7526DTF Fairchild Semiconductor, KA7526DTF Datasheet - Page 12

• Manufacturer Part Number: KA7526DTF
• Description: Power Factor Correction ICs PFC Controller
• Manufacturer: Fairchild Semiconductor

Specifications of KA7526DTF

• Start-up Supply Current: 300uA
• Operating Supply Voltage (max): 30V
• Operating Temp Range: -25C to 125C
• Operating Temperature Classification: Commercial
• Package Type: SOIC N
• Pin Count: 8
• Mounting: Surface Mount
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 25 C
• Lead Free Status / RoHS Status: Compliant

KA7526
Current Sense Comparator
The current sense comparator adopt the RS latch configuration to ensure that only a single pulse appears at the drive output
during a given cycle. MOSFET drain current is converted to voltage using an external sense resistor in series with the external
power MOSFET. When sense voltage exceeds the threshold set by the multiplier output, the current sense comparator
terminates the gate drive to the MOSFET and resets the PWM latch. The latch insures that the output remains in a low state
after the MOSFET drain current falls back to zero.
The peak inductor current under normal operating conditions is controlled by the multiplier output, Vmo.
Abnormal operating conditions occur during preconverter start-up at extremely high line or as output voltage sensing is lost.
Under these conditions, the multiplier output and current sense threshold will be internally clamped to 1.65V. Therefore, the
maximum peak switch current is limited to:
Ipk(max) = 1.65V / Rsense
An internal R/C filter has been included to attenuate any high frequency noise that may be present on the current waveform.
This circuit block eliminates the need for an external R/C filter otherwise required for proper operation of the circuit.
12
MULT
1.65V
3
+
-
Fig. 4.1 Current Sense Circuit
Fig.3.1 Multiplier Block
Current Sense
Comparator
1.65V
Multiplier
Output
Vm1
+
-
cs
4
Rsense
Vmo
CS
4
Vref
-
+
EA OUT
+
Vm2
+
2
Error Amp.
External R/C Filter
can be eliminated
+
-
INV
1