UH8615 Datasheet, PDF (4/9 Pages) Unisonic Technologies – HID LAMP CONTROLLER

UH8615
Preliminary
CMOS IC
 PIN FUNCTION DESCRIPTIONS (Cont.)
PIN NO.
19
20
21
22
23
24
26
27
28
FUNCTION
PWMOUT
GND
OSC
DIVPAUSE
I_SENSEIN
BAT
COMP
FB
5V_REF
DESCRIPTION
The output of the PWMOUT is the signal output of the pulse width modulator. it is used to
command a power MOSFET switch. In normal PWM-OUT can be directly connected to
the gate of an N-channel power MOSFET. And if the lead between the UTC UH8615 and
the MOSFET is longer than a few cm. A 10 ohm resistor from PWMOUT to the MOSFET
gate may be required.
Ground for IC is through this pin.
The frequency of the PWM in the UTC UH8615 can be generated by the pin. A 200pF
capacitor from OSC to GND programs the PWM frequency at 100kHz. In fact the actual
oscillator frequency is determined by both the capacitor from OSC to GND and the
resistor from ISET to GND
The QOUT and QOUT outputs switch lamp polarity in an AC ballast. when the lamp is
being lit, It is important to stop polarity switching to keep the arc across the electrodes
can form in the correct place. A high voltage on DIVPAUSE can stop the internal circuit
generates the QOUT and QOUT signals.
Connect a resistor from NOTON to DIVPAUSE and a capacitor from DIVPAUSE to GND,
will stop the divider when the lamp is being lit and start after the lamp has lit.
the UTC UH8615 HID Controller is built in a power regulation algorithm that can compute
a function of the lamp current and voltage. It computes the appropriate battery current to
keep lamp power constant. This current is sensed by a connection from I_SENSEIN pin to a
current sense resistor. This current sensed pulse width modulation scheme is often
referred to as current mode control. The UTC UH8615 also contains peak input current
limiting. It is limited 0.2V across the I_SENSEIN resistor during normal operation and 0.4V
during starting. The period from starting to normal operation is accomplished by the rise of
the WARMUPC capacitor. As the current mode control has a disadvantage that the loop
will enter chaotic oscillations at high duty cycle, the UTC UH8615 inherent the slope
compensation to prevent oscillation. An external resistor from I_SENSEIN to the current sense
resistor creates a voltage drop proportional to OSC voltage, which gives slope
compensation.
This input can detect excessively high input voltage and will shut down the IC if the input
voltage exceeds a set voltage. When connect BAT to a voltage divider across the input
supply, in order to protect the IC in the quite event, please keep divider impedance higher
than 10k.
COMP is drived by the amplifier which senses the difference between FB and 2.5V. a
capacitor should be connected from COMP to FB to keep the system stable.
The FB pin is the inverted input of error amplifier that senses the differences between the
commanded lamp power and desired lamp power. The output of the error amplifier drives
the comp.
The output of the internal 5V reference voltage that is used for setting currents and
thresholds and can also be used for other functions.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R118-019.a