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MXHV9910BTR

P1-P3P4-P6P7-P9P10-P12
I
NTEGRATED
C
IRCUITS
D
IVISION
MXHV9910
4 www.ixysic.com R04
1.4 Recommended Operating Conditions
1.5 Electrical Characteristics
Unless otherwise specified, all electrical specifications are provided for T
A
=25C.
1.6 Thermal Characteristics
1
Use of a four-layer PCB can improve thermal dissipation (reference EIA/JEDEC JESD51-5).
Parameter Symbol Minimum Nominal Maximum Unit
Input Voltage Range
V
IN
8 - 450
V
DC
PWMD Frequency
f
PWMD
- 500 - Hz
Operating Temperature
T
A
-40 - +85 °C
Parameter Conditions Symbol Minimum Typical Maximum Unit
Input
Input DC Voltage Range DC Input Voltage
V
IN
8 - 450
V
DC
Shut-Down Mode Supply Current
PWMD to GND, V
IN
=15 to 450V
I
INSD
-0.30.6mA
Maximum Voltage to V
DD
Pin External Voltage applied to V
DD
Pin
V
DDmax
--12V
Regulator
Internal Voltage Regulator
V
IN
=15V to 450V,
I
DD(ext)
=0,
GATE Output=Open
V
DD
7.2 7.8 8.4
V
DC
V
DD
Current Available
for External Circuitry
-
I
DD(ext)
--2mA
V
DD
Load Regulation V
IN
=15V, I
L
=1mA V
DD
- - 200 mV
PWM Dimming
PWMD Input Low Voltage
V
IN
=8V to 450V V
EN
(low)
--0.5
V
PWMD Input High Voltage
V
IN
=8V to 450V V
EN
(high)
2.4 - -
PWMD Pull-Down Resistance
V
IN
=12V, V
PWMD
=V
DD
R
EN
70 115 165 k
Current Sense Comparator
Current Sense (CS) Input Current
CS Low CS=0V
I
IL
--45-90
A
CS High
CS=V
DD
I
IH
-0±15
Current Sense Threshold Voltage
-40°C < T
A
< 85°CV
CS(high)
200 - 280 mV
Current Sense Blanking Interval
R
T
=400k t
BLANK
- 400 - ns
Delay from CS Trip to Gate Low
R
T
=400k t
DELAY
- 300 - ns
Oscillator
Oscillator Frequency (Gate Driver)
R
T
=400k f
S
51 64 77 kHz
Gate Driver
Gate High Output Voltage
I
OUT
= -10mA V
GATE
(hi) V
DD
-0.3
--
V
Gate Low Output Voltage
I
OUT
=10mA V
GATE
(lo)
- 0.03 0.3
Gate Output Rise Time
C
GATE
=500pF
t
RISE
-16-
ns
Gate Output Fall Time
C
GATE
=500pF
t
FAL L
-7-
Parameter Package Symbol Minimum Typical Maximum Unit
Thermal Resistance,
Junction-to-Ambient
SOIC-8 With Thermal Pad (BE)
1
R
JA
-50-
°C/W
SOIC-8 W/O Thermal Pad (B) - 128 -
I
NTEGRATED
C
IRCUITS
D
IVISION
MXHV9910
R04 www.ixysic.com 5
2. Functional Description
Figure 1 Typical Application Circuit
2.1 Overview
The MXHV9910 is a high-efficiency, low cost, off-line
LED driver designed using IXYS IC Division's state of
the art BCDMOS on SOI process. The driver can
operate from a DC supply voltage between 8 to
450V
DC
. The versatile input supply voltage range
enables this driver to be used in a broad range of
applications such as flat panel display RGB
backlighting, signage, decorative LED lighting, and
incandescent lamp replacement.
The MXHV9910 IC is configured in a buck converter
topology, which is a perfect choice for off-line and DC
applications driving multiple LEDs in series or parallel.
This method provides excellent efficiency and enables
a buck switcher design using a minimum number of
external components. An external current sense
resistor sets the peak current to the LED string. In
addition, LED dimming can be implemented by either
applying a DC control voltage to the LD pin, or by
applying a low frequency, pulse-width modulated
digital signal to the PWMD pin (typically 500 Hz).
2.2 LED Driver Theory of Operation
The gate driver pulse width mode (PWM) control
circuit is enabled by connecting the PWMD pin to the
V
DD
pin. When enabled, the rising edge of each
internal clock turns on the gate driver and the external
power MOSFET, causing the inductor current to ramp
up the voltage across the current sense resistor
located at the CS pin. When the rising voltage at the
current sense, CS, pin exceeds V
CS(high)
, the internally
set threshold, the gate drive signal goes low and turns
off the external power MOSFET. Turning the power
MOSFET off causes the inductor current to decay until
the next rising edge of the clock, and the process
repeats.
The peak current threshold is set by comparing the
voltage developed across the R
SENSE
resistor to the
internal threshold, V
CS(high)
. This default threshold can
be overridden externally by applying a voltage less
than V
CS(high)
to the LD pin. The lower of these two
thresholds limits the peak current in the inductor
A soft-start function can be implemented by slowly
ramping up the DC voltage at the LD pin from 0mV to
a level greater than 250mV. Figure 2 shows a typical
recommended soft-start circuit design.
Figure 2 Soft-Start RC Network
+
-
+
-
Voltage
Regulator
Voltage
Reference
PWM
Control
250mV
V
DD
V
IN
R
T
LD
GND
PWMD
GATE
CS
V
DD
6
8
1
7
5
3
4
2
8-450V
R
SENSE
OSC
MXHV9910
V
IN
CS
GND
GATE
R
T
LD
V
DD
PWMD
51kΩ
2kΩ 0.1μF
I
NTEGRATED
C
IRCUITS
D
IVISION
MXHV9910
6 www.ixysic.com R04
Figure 3 MXHV9910 Waveforms (From Application Circuit in Figure 6)
2.2.1 Input Voltage Regulator
The MXHV9910 has an internal voltage regulator that
can work with input voltages ranging from 12V
DC
to
450 V
DC
. When the input voltage applied at the V
IN
pin
is greater than 12V
DC
, the internal voltage regulator
regulates this voltage down to a typical 7.8V. The V
DD
pin is the internal regulator output pin and must be
bypassed by a low ESR capacitor, typically 0.1F, t o
provide a low impedance path for high frequency
switching noise.
The MXHV9910 driver does not require the bulky
start-up resistors typically needed for off-line
controllers. An internal voltage regulator provides
sufficient voltage and current to power the internal IC
circuits. This voltage is also available at the V
DD
pin,
and can be used as bias voltage for external circuitry.
The internal voltage regulator can by bypassed by
applying an external DC voltage to the V
DD
pin that is
slightly higher than the internal regulator’s maximum
output voltage. This feature reduces power dissipation
of the integrated circuit and is more suitable in isolated
applications where an auxiliary transformer winding
could be used to supply V
DD
.
The total input current drawn by the V
IN
pin is equal to
the integrated circuit quiescent current, which is
0.6mA maximum, plus the gate driver current. The
gate driver current is dependant on the switching
frequency and the gate charge of the external power
MOSFET.
The following equation can be used to approximate
the V
IN
input current:
Where Q
GATE
is the total gate charge of the external
power MOSFET, and f
S
is the switching oscillator
frequency.
2.2.2 Current Sense Resistor
The peak LED current is set by an external current
sense resistor connected from the CS pin to ground.
The value of the current sense resistor is calculated
based on the desired average LED current, the current
sense threshold, and the inductor ripple current.
The inductor is typically selected to be large enough to
keep the ripple current (the peak-to-peak difference in
the inductor current waveform) to less than 30% of the
average LED current. Factoring in this ripple current
requirement, the current sense resistor can be
determined by:
Where:
• V
csth
= nominal current sense threshold = 0.25V
• r
iout
= inductor ripple = 0.3
• I
LED
= average LED current
The power dissipation rating of the sense resistor can
be found with the following formula:
CH1:
50mA/div
F
S
65kHz
CH2:
CH3:
5mV/div x 10
Time Scale: 5s/div
Max 77mA
10V/div
P1-P3P4-P6P7-P9P10-P12

MXHV9910BTR

Mfr. #:
Buy MXHV9910BTR
Manufacturer:
IXYS Integrated Circuits
Description:
LED Lighting Drivers Off-Line High Bright LED Driver
Lifecycle:
New from this manufacturer.
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