UBA2024 NXP Semiconductors, UBA2024 Datasheet - Page 3

• Manufacturer Part Number: UBA2024
• Description: Half-bridge Power Ic For Cfl Lamps
• Manufacturer: NXP Semiconductors

Philips Semiconductors
PINNING
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 V
switched to ground. The start-up state is defined until
V
Sweep mode
The IC enters the sweep mode at the moment the voltage
on pin V
by I
circuit enters the start-up state again when the voltage on
pin V
2004 Feb 03
SW
SGND
FS
PGND
OUT
HV
V
RC
SYMBOL
DD
DD
Half-bridge power IC for CFL lamps
sweep
= V
DD
DD
DD(start)
< V
and the half-bridge circuit starts oscillating. The
> V
DD(stop)
DD
DD(start)
.
are charged. Pins RC and SW are
PIN
1
2
3
4
5
6
7
8
.
. The capacitor on pin SW is charged
sweep timing input
signal ground
high-side floating supply output
power ground
half-bridge output
high-voltage supply
internal low-voltage supply
output
internal oscillator input
DESCRIPTION
3
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 V
Oscillation
The oscillation is based upon the 555-timer function. With
the external resistor R
a self oscillating circuit is made, where R
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:
An overview of the oscillator signal, internal LS and HS
drive signals and the output is given in Fig.3.
handbook, halfpage
f
osc
=
-------------------------------------------- -
k R
Fig.2 Pin configuration DIP8 package.
OSC
PGND
SGND
1
SW
FS
C
1
2
3
4
OSC
OSC
UBA2024P
and capacitor C
MCE409
7
6
5
8
Product specification
RC
HV
OUT
V DD
UBA2024
OSC
OSC
and C
(see Fig.5)
FS(lock)
OSC
.