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HV9903 の電気的特性と機能

HV9903のメーカーはSupertex Incです、この部品の機能は「White LED Driver」です。


製品の詳細 ( Datasheet PDF )

部品番号 HV9903
部品説明 White LED Driver
メーカ Supertex Inc
ロゴ Supertex  Inc ロゴ 




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HV9903 Datasheet, HV9903 PDF,ピン配置, 機能
HV9903
Initial Release
White LED Driver
Features
Power efficiency of up to 85%
Drives up to 6 White LEDs
2.6V to 4.6V Supply
power stage can operate at 1.8V (see page 8)
Built-in Soft Start
DC and PWM Dimming Control
Built-in Open LED protection
Open LED indicator (via RSET)
1.2MHz Fixed Switching Frequency
500nA max leakage current when disabled
No leakage current path through LEDs when
disabled
Resistor-programmable LED Current
Small 6-lead MLP (3mm x 3mm) package
(similar to 6-pin SOT-23)
Applications
Color LCD Backlighting
Cell phones, smart phones
PDAs, pocket PCs
Organizers
Digital Cameras
MP3 Players
Description
The Supertex HV9903 is a fixed frequency DC-DC
boost converter designed for driving Light Emitting
Diodes (LEDs) with constant current where the light
intensity is proportional to the current through them.
The input supply voltage range into the device (VDD)
is 2.6 to 4.6V. Operation of the driver at lower
voltages is possible as long as a 2.6–4.6V low-
current supply is available for the HV9903. The
device uses a single inductor and a minimum
number of passive components. The device can be
enabled/disabled via the SHDN pin.
The HV9903 has an internal oscillator. The oscillator
frequency is at fixed frequency of 1.2MHz that allows
use of small value inductors. The LED current can
be adjusted from 5 to 40mA by an external resistor
connected between the RSET and the GND pins. The
amount of current though the LED can also be
adjusted via DC voltage or a pulse width modulated
(PWM) signal to the RSET pin.
Soft-start is implemented on-chip, minimizing inrush
current to only 30% over steady state current.
An open LED circuit detects an open LED condition,
disables the driver, and sets the RSET pin high. The
driver is re-enabled by asserting SHDN low, then
high. If the open LED condition persists, the driver
will again latch off.
Typical Application
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products
liability indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be
defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product
specifications, refer to the Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer
page on the Supertex website.

1 Page





HV9903 pdf, ピン配列
HHVV99990033
Symbol Parameter
Min Typ. Max Unit Conditions
ISHDN
SHDN input current
-100
nA VSHDN = 0V
100 VSHDN = 2V
fSW Inductor switching frequency
0.8 1.2 1.6 MHz VDD = 2.6 to 4.6V
DMAX Maximum duty cycle
90 95
%
VIL IC Shutdown voltage (SHDN pin),
Off
VIH IC Start-up voltage (SHDN pin),
On
1.2
0.9
V
VOpen Open LED indicator at RSET lead
2.0 VDD- VDD
0.4V
V VOUT > 33V, RSET = 562, VDD =
2.7V
ISW(off) Switch Off leakage current
100 nA VSW = 5V
Pin Configuration
SW
GND
LED
VDD
SHDN
RSET
Top View
GND
Pin 1
Bottom View
Pin Name Description
1 SW Internal switch connection.
2 GND Ground. The underside pads are internally connected to pin 2.
3 LED Cathodes of the LEDs are connected to this pin.
4 RSET For programming the LED current and dimming function.
Also functions as a Fault output to indicate an open LED condition. RSET
is pulled to VDD when an open LED condition is detected. The driver is
then latched off. To reset, the SHDN input must be asserted low.
An externally applied voltage greater than 100mV causes the LED
switch and PWM boost converter to shut off. The IC does not go into
low power standby and the soft-start circuit is not reactivated when VRset
again falls below 100mV.
5 SHDN Shut down input. A logic low disables the IC and places it in low power
standby. A logic high enables the IC via a soft-start sequence.
6 VDD Input voltage supply pin. It is common practice to use a bypass
capacitor as close as possible to the device on this pin.
3


3Pages


HV9903 電子部品, 半導体
HHVV99990033
lower standard value is 3.3µH (10% tolerance) and
the corrected rating is then:
ICORRECTED
320mA
3.7µH
3.3µH
359mA
Inductor data sheets may rate the inductor in terms of
DC current, RMS current, or saturation current. The
DC or saturation ratings should be used. Confirm that
the inductor is not saturating by observing the SW pin.
When an inductor saturates, current begins to climb
rapidly. This condition is evidenced by a breakpoint in
the SW voltage waveform as indicated in the diagram
below. Normally, the voltage at the SW pin should be
a fairly linear ramp, as the linear rise in inductor
current through the SW resistance produces a linear
voltage ramp. When the inductor saturates, the rapid
rise in current produces a likewise rapid rise in SW
voltage. Test using an HV9903 with a low switching
frequency.
SW Waveform Showing Inductor Saturation
VIN
Gnd
Normal
Saturated
indicated when the SW voltage is at the supply
voltage level (with some ringing).
The following graphs show the SW waveform with
various inductor values and can assist in selecting an
inductor. The top graph shows an inductor value that
is acceptable, however, greater efficiency can be
achieved by increasing inductance. The bottom graph
shows continuous mode operation, which must be
avoided.
SW Waveform with Various Inductor Values
Inductance too low
VIN
Gnd
tiidmlee
Inductance ideal
VIN
Gnd
VIN
Gnd
Inductance too high
(continuous mode)
Gnd
Note: ringing or noise may be present.
Also, confirm that the driver is operating in
discontinuous mode by observing the voltage at the
SW pin while at minimum supply and maximum LED
current. For worst-case test purposes, select
components within their tolerance range as follows:
Inductor: high value
LED: high voltage drop
HV9903: high switching frequency
Some ringing in the SW waveform will be evident, but
is not a concern as the energy is very low. About 10-
15% idle time should be allowed to assure
discontinuous mode operation. Idle time is the
interval when there is no inductor current flowing, as
Capacitor Selection
Proper selection of CDD and COUT is essential to the
efficient operation of the LED driver. Both CDD and
COUT should be around 1µF with good high frequency
characteristics (low ESR and ESL). Ceramic
capacitors are a practical choice for their high
volumetric efficiency and good high frequency
characteristics, but pay attention to the capacitor’s
voltage coefficient. Some small, high value ceramic
capacitors can lose 75% of their capacitance at their
rated voltage! X5R, Y5V, and Z5U formulations are
more susceptible to this effect, as well as possessing
higher temperature coefficients. X7R formulations are
a better choice.
The voltage rating of CDD should be greater than the
maximum supply voltage. To be compatible with the
HV9903’s open LED protection, COUT’s voltage rating
should be 35V or more.
6

6 Page



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