UBA2017 datasheet(13/29 Pages) PHILIPS

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UBA2017

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Product data sheet

Rev. 2 — 15 May 2012

13 of 29

NXP Semiconductors

UBA2017/UBA2017A

600 V fluorescent lamp driver with linear dimming function

However, the switching frequency can never go below fsw(low). If the regulation level is not

reached at fsw(low) the IC will stay at fsw(low) (point E in Figure 7).

7.3.7.2

Operation without lamp current control

To operate the lamp without current control the lamp current sense, pin IFB must be

connected to ground. The lamp now operates at the lowest frequency fsw(low) (point E in

Figure 7). Dimming is not supported in this case.

7.3.8 Stop state

When in the Stop state, the IC is off and all driver outputs are low. The IC will remain in the

Stop state until the voltage on pin VDD drops below Vrst(VDD) or it is disabled, in which

case it will go to the Reset state.

The sequence of events for entering the Stop state are shown in Figure 6 “State diagram”.

7.4 Enable and Disable

The enable function works via pin PH/EN. If this pin is pulled below the enable voltage

Ven(PH/EN), the IC goes into the Standby state (immediately if GLHB is high, otherwise it

will continue its normal clock cycle until GLHB is high and then go to the Standby state).

The external interface with pin PH/EN for the enable signal should be an open collector or

open drain type driver. To enable the IC, the open collector or open drain should be open

(high ohmic) to not disturb the fixed frequency preheat setting function of pin PH/EN.

In the Restart, Standby and Stop states, the standby pull-up current source Ipu(stb)(PH/EN)

will pull the voltage at pin PH/EN above Ven(PH/EN). In the Preheat, Ignition and Burn

states, the normal output voltage driver of the IC will pull the pin high. In those cases, the

external driver must draw a current Iclamp(PH/EN) from the pin to disable the IC.

7.5 Protection circuits

7.5.1 End-of-life rectifying lamp detection

If voltage on pin EOL is below low threshold voltage Vth(low)EOL or above Vth(high)EOL, the

fault timer will start.

A programmable end-of-life window is achieved by the internal bias current sink Ibias(EOL).

The effective relative size of the EOL window will decrease in line with the increasing

series resistance connected to pin EOL.

The end-of-life lamp rectifying detection is only active during the Burn state.

7.5.2 End-of-life overvoltage detection

This protection is intended to protect against symmetrical lamp aging. When in the Burn

state, the voltage on pin VFB exceeds the overvoltage end-of-life threshold voltage

Vth(oveol)(VFB) by more than 50 % of each switching cycle the fault timer will start.

Vth(oveol)(VFB) is related to the regulation voltage on pin IFB Vreg(IFB) that itself is dependent

on the voltage on pin DIM (see Section 7.3.7.1 “Lamp current control and dimming”)

according to the formula

Parameters a and b can be calculated from the Vth(oveol)(VFB) values given in Table 6.

th oveol

() VFB

()

reg IFB

()

–

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