KA7543 Fairchild Semiconductor, KA7543 Datasheet - Page 8

• Manufacturer Part Number: KA7543
• Description: MOSFET & Power Driver ICs
• Manufacturer: Fairchild Semiconductor

Specifications of KA7543

• Product: Half-Bridge Drivers
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

KA7543
Dimming Control Stage
The condition for full dimming is when the Vdm voltage is 2V and the condition for full lighting is when the Vdm voltage is
0V. Dimming operation starts when Vcs becomes 4V and the change rate of dimming is determined by the capacitor
connected to the Cdm pin. The more smooth dimming can be accomplished by the larger capacitor connected to the Cdm pin.
If the Vdm pin voltage is higher than 5V, then the output drive stage remains in off state. Dimming control and output drive on/
off control can be achieved with only one pin.
Output Drive Stage
OUT1 and OUT2 are complementary and there is 1.4us dead time for the ZVS operation. The structure of output stage is the
totem-pole output stage. For the high side MOSFET drive, a pulse transformer is necessary.
No Lamp Protection
If the Vld pin voltage is lower than 1V, it means that there is no lamp connected. On no lamp condition, the output drive stage
is in off state.
8
To error amp (+)
is
From oscillator
is-id
+
-
Q
id
From protection output from uvlo
Figure 5. Dimming Control Stage
To output
Figure 6. Output Drive Stage
Mirror
Frequency
divider
idr
Switch
20k
+
-
Output
stage
5V
Dimmer
+
+
-
14
2V
1
11
9
OUT1
OUT2
Cdm
Vdm
CURRENT
AMPLIFIER
DIMMING
CONTROL