HV9910BDB3 Supertex, HV9910BDB3 Datasheet - Page 2

• Manufacturer Part Number: HV9910BDB3
• Description: LED Lighting Development Kits LO VOLT HI BRIGHT LED DRIVER DEMOBOARD
• Manufacturer: Supertex

Frequently Asked Questions
1. Why does the demoboard have two operating modes?
2. If the minimum input voltage in my application is higher (say 20V), does that mean I can drive a 9V LED string
3. How can I compute the maximum LED current the demoboard can deliver if I use a higher input voltage and a
Parameters
Constant frequency mode limits the maximum output voltage to less then 50% of the minimum input voltage. So, in
this case, if we use only the constant frequency mode, the maximum output voltage will have to be less than 5V. Con-
stant off-time mode removes this limitation and allows the output voltage become higher. However, in order to achieve
reasonable noise immunity and to limit the switching frequency variation over the input voltage range, it is not recom-
mended to operate the HV9910DB3 with the output voltage exceeding 80% of the input voltage, even in the constant
off-time mode. Please refer to application note AN-H50 on the Supertex website for more details.
Although a larger LED string can be driven using the demoboard in these conditions, the demoboard will not be able to
drive the LED at 1A.
The HV9910B is a constant peak current controller. The average LED current is equal to the peak current set (using the
sense resistor) minus one-half of the ripple current in the inductor.
Higher output voltages lead to larger ripple current values, which will reduce the maximum LED current the board can
deliver.
Maximum Switching Frequency =
in the constant frequency mode or an 16V LED string in the constant off-time mode using the
demoboard?
higher LED string voltage?
Constant Off-Time Mode
Δl =
I
LED
Minimum input voltage
Maximum LED string voltage
Switching frequency (constant frequency mode)
Off-Time (constant off-time mode)
HV9910B CS threshold voltage
Sense Resistor
Inductor
=
V
V
R
O,MAX
CS
CS
L
• T
–
●
OFF
Δl
2
1235 Bordeaux Drive, Sunnyvale, CA 94089
{
1 –
T
V
V
OFF
O, MAX
IN,MIN
{
2
●
Tel: [phone]
Constant Frequency Mode
Δl =
V
O,MAX
I
LED
=
= V
= V
= f
= T
= V
= R
= L
•
S
●
V
R
OFF
L • f
IN,MIN
O,MAX
CS
{
CS
CS
1 –
CS
www.supertex.com
S
–
V
V
O, MAX
IN,MIN
Δl
2
HV9910BDB3
{
(100kHz)
(5.1μs)
(0.25V)
(0.22Ω)
(220μH)