MXHV9910B Clare, MXHV9910B Datasheet - Page 5

• Manufacturer Part Number: MXHV9910B
• Description: IC LED DRIVER HIGH BRIGHT 8-SOIC
• Manufacturer: Clare
• Type: HBLED Driverr

Specifications of MXHV9910B

• Topology: AC DC Offline Switcher, PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Backlight
• Type - Secondary: High Brightness LED (HBLED), RGB
• Frequency: 51kHz ~ 77kHz
• Voltage - Supply: 8 V ~ 450 V
• Voltage - Output: 7.8V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Operating Temperature: -40°C ~ 85°C
• Internal Switch(s): No
• Efficiency: 90%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -

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 Clare's state of the art
BCDMOS on SOI process. The driver can operate
from a DC supply voltage between 8 to 450V
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
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
R01
DD
pin. When enabled, the rising edge of each
8-450V
V
DD
6
1
8
7
5
3
V
PWMD
GND
LD
V
R
DD
IN
Reference
T
Voltage
250mV
Regulator
Voltage
DC
OSC
. The
+
+
www.clare.com
-
-
Control
located at the CS pin. When the rising voltage at the
current sense, CS, pin exceeds V
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
internal threshold, V
be overridden externally by applying a voltage less
than V
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.
recommended soft-start circuit design.
Figure 2 Soft-Start RC Network
PWM
CS(high)
V
CS
GND
GATE
IN
MXHV9910
to the LD pin. The lower of these two
PWMD
CS(high)
GATE
CS
V
LD
R
DD
T
4
2
. This default threshold can
Figure 2
SENSE
2kΩ
CS(high)
R
SENSE
shows a typical
resistor to the
51kΩ
, the internally
MXHV9910
0.1μF
5