uba20270 NXP Semiconductors, uba20270 Datasheet - Page 6

• Manufacturer Part Number: uba20270
• Description: 600 V Driver Ic For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20270
Product data sheet
7.1.1 Reset state
7.1.2 Start-up state
7.1.3 Preheat state
7.1 Lamp start-up cycle
The UBA20270 is in a reset state while the supply voltage on the V
V
counters and timers are undefined. In addition, the hold state latch is reset and both the
applied external high and low-side transistor (Q1, Q2) are non-conductive. During
power-up, the low voltage supply capacitor on the V
start-up resistor. When the voltage on the V
state is entered. The UBA20270 enters the reset state when the supply voltage on the
V
Start-up is achieved by charging the low voltage supply capacitor on the V
external start-up resistor. At start-up the High-Side (HS) transistor is non-conductive and
the Low-Side (LS) is conductive to enable charging of the bootstrap capacitor. This
capacitor supplies the HS driver and level shifter circuit connected between the FS and
HBO pin. A DC reset circuit is incorporated in the ICs HS driver. This circuit ensures that
lower than the lockout voltage on the FS pin the output voltage (V
As the start-up state is entered, the circuit only starts oscillating when the low voltage
supply (V
oscillating at f
The circuit enters the preheat state as soon as the capacitor on the CP pin is charged to a
voltage level above V
than V
on the DCI pin must be higher than V
An UnderVoltage LockOut (UVLO) is implemented on the DCI pin to create a guaranteed
turn-off for multiple lamps when the lamps are at low dim levels. The UVLO also
guarantees that there is a preheat phase when the dim level is turned up again.
The typical turn-on level on the DCI pin is set to lower than V
increases the turn-on hysteresis of the lamp. This level enables the UBA20270 to perform
a stable ignition of the lamp when there is already sufficient power from the dimmer at
lower dim levels.
During the start-up state, the voltage on the CF pin is at zero and the CB pin is close to
zero. The voltage on the CP pin rises to higher than V
state. See
Starting at f
current circuit controlled by the preheat current sensor circuit. This state continues until
the momentary value of the voltage across sense resistor R
fixed preheat voltage level (SLS pin). At this level, the current of the preheat current
sensor reaches a charge and discharge balanced state on capacitor C
frequency.
DD(rst)
DD
pin drops lower than V
DD(stop)
level. In the reset state, a part of the internal supply is turned off, all registers,
DD
Figure
bridge(max)
) reaches the value of V
bridge(max)
and lower than the upper limit V
All information provided in this document is subject to legal disclaimers.
9.
, the frequency decreases by charging capacitor C
th(CP)max
Rev. 2 — 8 September 2011
.
DD(rst)
600 V Driver IC for dimmable compact fluorescent lamps
. To remain oscillating, the V
.
DD(start)
th(start)DCI
AND V
DD
DD(clamp)
pin is above the V
 V
th(hys)DCI
i(DCI)
DD
. In addition, the typical voltage level
th(CP)max
pin is charged via an external
> V
DD
th(start)DCI
= 0.24 V.
SLS
th(start)DCI
voltage must remain higher
level during the start-up
reaches the internally
DD(rst)
GHS
DD
UBA20270
. The circuit starts
- V
pin is below the
= 0.36 V, else it
CI
level, the start-up
© NXP B.V. 2011. All rights reserved.
CI
to set the
HBO
via an output
DD
) is zero.
pin via an
6 of 32