AN2640 datasheet(20/36 Pages) STMICROELECTRONICS

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L6382D5 - power management units for microcontrolled ballast

AN2640

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sense resistor. As the voltage on pin CSI can go negative, the current must be limited below

2 mA by external components.

4.2

Use of the pins

A short description of each pin function is given below.

●

Pin 1: PFI. This pin receives a digital input signal from the ST7 micro to control the PFC

gate driver. We advise connecting a capacitor for noise filtering between this pin and

GND. In this application a 33pf capacitor is used.

●

Pin 2: LSI. This pin receives digital input signal from the ST7 to control the low side

switch in the ballast.

●

Pin 3: HSI. This pin receives digital input signal from the ST7 to control the high side

switch in the ballast.

●

Pin 4: HEI (not used). This pin receives digital input signal from the ST7 to control the

HEG driver.

●

Pin 5: PFG. This pin is able to drive an external MOSFET with a sink current capability

of 120 mA and a source current capability of 250 mA. A 10

Ω resistor is connected

between this pin and the Power MOSFET gate to reduce the peak current.

●

Pin 6: not connected

●

Pin 7: TPR. This pin is connected by means of an RC net to the half-bridge midpoint in

order to form a charge pump circuit charging the capacitor connected to the VCC pin. In

this application a capacitor of 1 nF at 630 V and a resistor of 44

Ω (2 x 22 Ω) have been

mounted. The high voltage capacitor in this connection also performs the snubber

function in the half-bridge section limiting the slope during the voltage variation.

●

Pin 8: GND. On the GND traces it is better to keep separate power traces from the

signal and a star connection of these tracks is advisable.

●

Pin 9: LSG. This pin is connected to the Power MOSFET gate of the low side of the

half-bridge. This pin has 120 mA as source and sink current capability. A 33

Ω resistor

is connected between this pin and the MOSFET gate to limit the peak current. At turnoff

a net composed of a diode and a 33

Ωresistor reduces the resistance which decreases

the turnoff time.

●

Pin 10: VCC. This pin provides the supply voltage to the driver. A capacitor of 47 µF is

connected between this pin and GND and in parallel another small capacitor is

mounted.

●

Pin 11: BOOT. This pin provides the supply voltage at the high side gate driver. A

100 nF capacitor is connected between this pin and the out pin of the driver. This

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