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UBA2024 View Datasheet(PDF) -

Part Name
Description
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UBA2024
 
UBA2024 Datasheet PDF : 0 Pages
Philips Semiconductors
Half-bridge power IC for CFL lamps
Product specification
UBA2024
PINNING
SYMBOL
SW
SGND
FS
PGND
OUT
HV
VDD
RC
PIN
DESCRIPTION
1
sweep timing input
2
signal ground
3
high-side floating supply output
4
power ground
5
half-bridge output
6
high-voltage supply
7
internal low-voltage supply
output
8
internal oscillator input
handbook, halfpage
SW 1
8 RC
SGND 2
7 VDD
UBA2024P
FS 3
6 HV
PGND 4
5 OUT
MCE409
Fig.2 Pin configuration DIP8 package.
FUNCTIONAL DESCRIPTION
Supply voltage
The UBA2024 is powered by a supply voltage applied to
pin HV. The IC generates its own low supply voltage for
the internal circuitry and therefore, an additional external
low-voltage supply is not required.
Start-up state
With an increase of the supply voltage on pin HV, the IC
enters the start-up state. In the start-up state the high-side
power transistor is not conducting and the low-side power
transistor is switched on. The internal circuit is reset and
the capacitors on the bootstrap pin FS and low-voltage
supply pin VDD are charged. Pins RC and SW are
switched to ground. The start-up state is defined until
VDD = VDD(start).
Sweep mode
The IC enters the sweep mode at the moment the voltage
on pin VDD > VDD(start). The capacitor on pin SW is charged
by Isweep and the half-bridge circuit starts oscillating. The
circuit enters the start-up state again when the voltage on
pin VDD < VDD(stop).
Reset
A DC reset circuit is incorporated in the high-side driver.
The high-side transistor is switched off when the voltage
on pin FS is below the high-side lockout voltage VFS(lock).
Oscillation
The oscillation is based upon the 555-timer function. With
the external resistor ROSC and capacitor COSC (see Fig.5)
a self oscillating circuit is made, where ROSC and COSC
determine the oscillating frequency.
To realize an accurate 50% duty cycle, an internal divider
is used. Due to the presence of the divider, the bridge
frequency is half the oscillator frequency.
The output voltage of the bridge will change at the falling
edge of the signal on pin RC. The design equation for the
half-bridge frequency is:
fosc = -k----×-----R----O----S----C1----×-----C-----O----S---C--
An overview of the oscillator signal, internal LS and HS
drive signals and the output is given in Fig.3.
2004 Feb 03
3
 

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