HV9963NG-G データシートの表示（PDF） - Supertex Inc

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HV9963NG-G

Closed Loop LED Driver with Enhanced PWM Dimming

Supertex Inc 

HV9963

When the load is disconnected in a boost converter, the

output voltage rises as the output capacitor starts charging.

When the output voltage reaches the OVP rising threshold,

the HV9963 detects an over voltage condition and turns off

the converter. The converter is turned back on only when the

output voltage falls below the falling OVP threshold (which

is 10% lower than the rising threshold). This time is mostly

dictated by the R-C time constant of the output capacitor CO

and the resistor network used to sense over voltage (ROVP1

+ ROVP2). In case of a persistent open circuit condition, this

cycle keeps repeating; maintaining the output voltage within

a 10% band.

In most designs, the lower threshold voltage of the over volt-

age protection (VOVP – 10%) -- the point at which the HV9963

attempts to restart-- will be more than the LED string voltage.

Thus, when the LED load is reconnected to the output of the

converter, the voltage differential between the actual output

voltage and the LED string voltage will cause a spike in the

output current. This causes a short circuit to be detected and

the HV9963 will trigger short circuit protection. This behavior

continues until the output voltage becomes lower than the

LED string voltage at which point, no fault will be detected

and normal operation of the circuit will commence.

Pin Description

Pin # Name Description

1

VIN

This pin is the input of a 40V high voltage regulator, and should not be left unconnected. If a voltage at

PVDD is being applied from an external power supply, the VIN and PVDD pins should be shorted.

2

PVDD

This pin is a regulated 10V supply for the two gate drivers (FLT and GATE). It must be bypassed with a

low ESR capacitor to GND (at least 1.0μF).

3 GATE This is the GATE driver output for the switching FET.

4

GND

Ground return for all the low power analog internal circuitry as well as the gate drivers. This pin must be

connected to the return path from the input.

5

CS

This pin is used to sense the source current of the external power FET. It includes a built-in 100ns (min)

blanking time.

6 HCP This pin provides the hiccup timer in case of a fault. A capacitor at this pin programs the hiccup time.

This pin sets the frequency of the power circuit. A resistor between RT and GND will program the circuit

7

RT in constant frequency mode. The switching frequency is synchronized to the PWMD input and oscillator

will turn on once PWMD goes high.

8

SYNC

This I/O pin may be connected to the SYNC pin of other HV9963 circuits and will cause the oscillators to

lock to the highest frequency oscillator.

9

SS

This pin is used to provide soft start upon turn-on of the IC. A capacitor at this pin programs the soft start

time.

This is a power supply pin for all internal control circuits. This voltage is also used as the reference

10 AVDD voltage both internally and externally. It must be bypassed with a low ESR capacitor to GND (at least

0.1μF).

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FLT

This pin is used to drive an external disconnect FET which disconnects the load from the circuit during

a fault condition or during PWM dimming to achieve a very high dimming ratio.

This pin provides the over voltage protection for the converter. When the voltage at this pin exceeds

12 OVP 1.25V, the gate output of the HV9963 is turned off and FLT goes low. The IC will turn on when the voltage

at the pin goes below 1.125V.

13

PWMD

When this pin is pulled to GND (or left open), switching of the HV9963 is disabled. When an external TTL

high level is applied to it, switching will resume.

14

COMP

Stable Closed loop control can be accomplished by connecting a compensation network between COMP

and GND.

The voltage at this pin sets the output current level. The current reference can be set using a resistor

15 IREF divider from the AVDD pin. Connecting a voltage greater than 1.25V at this pin will disable the short

circuit comparator.

16

FB This pin provides output current feedback to the HV9963 by using a current sense resistor.

● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com

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