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Datasheet MT7910 PDF ( 特性, スペック, ピン接続図 )

部品番号 MT7910
部品説明 High Brightness LED Driver
メーカ Maxic Technology
ロゴ Maxic Technology ロゴ 
プレビュー
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MT7910 Datasheet, MT7910 PDF,ピン配置, 機能
  MT7910
High Brightness LED Driver
DESCRIPTION
The MT7910 is a hysteresis current mode control
LED driver IC. The MT7910 operates in constant
off-time mode. It allows efficient operation of
High Brightness (HB) LEDs from voltage sources
ranging from 14VDC up to 450VDC or 85VAC ~
265VAC. The MT7910 includes a PWM dimming
input that can accept an external control signal
with a duty ratio of 0 - 100% and a frequency of
up to a few kilohertz. It also includes a 0 - 245mV
linear dimming input which can be used both for
linear dimming and temperature compensation of
the LED current.
The MT7910 is ideally suited for buck LED
drivers. Since the MT7910 operates in hysteresis
current mode control, the controller achieves
good output current regulation without the need
for any loop compensation. Further, with Maxic
proprietary control technology (patent pending),
MT7910 achieves precision output current
accuracy from 85VAC ~ 265VAC. PWM dimming
response is limited only by the rate of rise and
fall of the inductor current, enabling very fast rise
and fall times.
Frequency jittering is used to reduce the EMI.
FEATURES
Proprietary constant-current control. Great
LED current accuracy.
Wide input range from 14VDC to 450VDC or
85VAC to 265VAC
Application from a few mA to more than 1A
output
Up to 92% efficiency
Up to hundreds of LEDs
Linear and PWM dimming capability
Requires few external components for
operation
Temperature compensation to regulate LED
current
Embedded Over-temperature, LED open
circuit, LED short-circuit protection
SOP-8 package
APPLICATION
DC/DC or AC/DC LED driver applications
RGB backlighting LED driver
General purpose constant current source
Signal and decorative LED lighting
E14/E27/PAR30/PAR38/GU10 LED lamp
TYPICAL APPLICATION CIRCUIT
MT7910 Rev. 2.0
www.maxictech.com
Copyright © 2009 Maxic Technology Corporation
Page 1

1 Page



MT7910 pdf, ピン配列
ABSOLUTE MAXIMUM RATINGS
VIN / VDD / GATE Pin
All other pins
ESD (HBM)
Storage Temperature
Thermal Resistance
Junction to ambient (RθJA)
  MT7910
High Brightness LED Driver
-0.3V to +16V
-0.3V to +6V
±4000V
-55°C to 150°C
128°C/W
ELECTRICAL CHARACTERISTICS
(Test conditions: TA=25°C unless otherwise stated.)
Symbol
VDC
VDD
VIN
Iin
Description
Conditions
Min Typ Max
Connect an appropriate
Input DC supply voltage resistor from DC supply
range
voltage to VIN pin and
14
450
VDD pin
Get power from DC
Internal regulated voltage
power rail through a
10
resistor or transistor
Internal regulated voltage for Connect to DC power
line compensation
rail through a resistor
12
Operating current
Gate floating
0.5
Under Voltage lockout
UVLO
Under voltage lockout
ΔUVLO UVLO hysteresis
VDD rising.
VDD falling
8
2
Enable
VEN(lo)
VEN(hi)
REN
PWMD input low voltage
PWMD input high voltage
PWMD pull up resistance
Linear Dimming
VLD Linear dimming low voltage
Linear dimming high voltage
1.2
2
300
50
245
Current sense stage
Vcs
Current sense
threshold voltage
pull-in
BIN1
BIN2
BIN3
208 217 226
235 245 255
258 269 280
Tblank
Toff
Ioff
Current sense blank time
Off time
Off time current
TOFF Pin floating
430
200
20
Unit
V
V
mA
V
V
V
V
K
mV
mV
mV
mV
mV
ns
ns
uA
MT7910 Rev. 2.0
www.maxictech.com
Copyright © 2009 Maxic Technology Corporation
Page 3


3Pages


MT7910 電子部品, 半導体
¾ In some cases, it may not be possible to find
the exact RCS value required to obtain the LED
current when the internal 245mV is used. In
these cases, an external voltage divider from the
VDD pin (Pin 2) can be connected to the LD pin
to obtain a voltage (less than 245mV)
corresponding to the desired voltage across RCS.
¾ Linear dimming may be desired to adjust the
current level to reduce the brightness of the
LEDs. Connecting a resistor between VDD pin
(Pin 2) and the LD pin (Pin 4), and also
connecting an NTC thermistor between LD pin
and ground (refer to Fig.3). The MT7910 is able
to realize the temperature compensation function.
(See more detail in Temperature
Compensation section)
The use the internal 245mV, the LD pin must be
connected to PWMD pin.
LD pin also works as enable pin. Pull LD pin to
low (less than 50mV), MT7910 enters into
shutdown mode. GATE goes low to turn off the
external MOSFET. Applying a control voltage
higher than 245mV will not change the output
current setting. When higher current is desired,
select a smaller sense resistor.
LD pin can’t leave floating. When no analog
dimming is required, even during PWM dimming,
LD pin can short with PWMD pin to get the input
level.
PWM Dimming
PWM Dimming can be achieved by driving the
PWMD pin (Pin 3) with a low frequency square
wave signal. When the PWM signal is low, the
GATE driver is disabled; and when the PWMD
signal is high, the GATE driver is enabled. The
PWM signal can be generated by a
microcontroller or a pulse generator with a duty
cycle proportional to the amount of desired light
output. This signal enables and disables the
converter modulating the LED current in the
PWM fashion. In this mode, LED current can be
  MT7910
High Brightness LED Driver
in one of the two states: zero or the normal
current set by the current sense resistor. Since
the PWMD signal does not turn off the other
parts of the IC, the response of the MT7910 to
the PWMD signal is almost instantaneous. The
rate of rise and fall of the LED current is thus
determined solely by the rise and fall times of the
inductor current.
To disable PWM dimming function, leave the
PWMD pin floating.
Temperature Compensation
MT7910 provides thermal protection for LEDs.
Refer to Fig.3, applying a NTC thermistor close
to the LEDs string will realize the temperature
compensation of LEDs current. If the
temperature of the LEDs rises, the resistance of
the NTC thermistor decreases until the voltage of
the LD pin falls below 245mV. Then the average
current is controlled by the LD pin and the
temperature compensation function starts. The
formula is as below:
RNTC VDD = 245mV
R1 + RNTC
Here VDD=10V. Assuming a 70% ripple in the
inductor, the temperature compensated
continues current may be computed as:
I out
=
(R1
+
RNTC VDD
RNTC ) RCS
1.35
Make sure the value of R1 is more than 5K.
When the LD pin voltage reduces to less than
50mV, the chip is shutdown.
After the ambient temperature returns to a safe
temperature, the current will return to the set
value.
Power Factor Correction
When the input power to the LED driver does not
exceed 25W, a simple passive power factor
correction circuit consisting of 3 diodes and 2
MT7910 Rev. 2.0
www.maxictech.com
Copyright © 2009 Maxic Technology Corporation
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