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AOZ1978 데이터시트 PDF




Alpha & Omega Semiconductors에서 제조한 전자 부품 AOZ1978은 전자 산업 및 응용 분야에서
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부품번호 AOZ1978 기능
기능 Dual Channel High Voltage LED Driver IC
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AOZ1978 데이터시트, 핀배열, 회로
AOZ1978
Dual Channel High Voltage
LED Driver IC
General Description
The AOZ1978 is a dual-channel high-efficiency LED
driver controller for high voltage LED backlighting
applications. It is designed to independently drive
two high-brightness LED light bars in LED TV
applications. The AOZ1978 can support a wide
range of input and output voltages. The input bias
voltage range of AOZ1978 is from 8V to 18V.
The AOZ1978 has multiple features to protect the
regulator under fault conditions. A control pin can
disable an external switch to disconnect the LEDs
current path from the output in PWM dimming or
under catastrophic failure conditions. Cycle-by-cycle
current protection limits the peak inductor current.
Thermal shutdown provides another level of
protection. An output flag to indicate the fault
condition if output of any channel is shorted to
ground.
Low feedback voltage (500mV) helps to reduce
power loss.
The AOZ1978 is available in a standard SO-20
package and operates over the temperature range of
-40C to +85C.
Typical Application
Features
8V to 18V input bias voltage
180Out of phase channel switching provides
input ripple current cancellation
18V driving capability at GATE pins
Disconnect control pin for PWM dimming or fault
conditions
Flag to indicate output short or fault condition
500mV feedback regulation
External reference input and Analog Dimming
capability
8 bit PWM dimming resolution
Cycle-by-cycle current limit
Output over-voltage protection
LED short and open protection
Thermal shutdown protection
SO-20 package
Applications
LCD TV LED backlight
Rev. 1.0 January 2012
www.aosmd.com
Page 1 of 1




AOZ1978 pdf, 반도체, 판매, 대치품
AOZ1978
Pin Functions
Pin1: VIN
This is the input supply for the controller IC; it is also
the voltage drive for the Gates and DPWM drivers. If
the input power of the boost converter is less than
18V, VIN can be connected directly to the boost
supply voltage. If the boost supply voltage is higher
than 18V, a separate supply rail between 8V and 18V
is required for the VIN pin. It is recommended that an
RC filter should be added between VIN and Boost
supply if they are connected directly.
PIN 2: DPWM1
This is the driver output for the gate of the LED
current control NMOS switch for channel 1. DPWM1 =
LOW if Pin 7 DBRT1 signal is low or fault condition is
triggered. The DPWM1 = HIGH if DBRT1 is high
under normal operating conditions. The high voltage
at DPWM1 equals to Pin1 VIN voltage. It is
recommended to add 1resistor between this pin and
NMOS gate. The resistor value can be optimized
depending on the LED current and selection of
NMOS. DPWM1 can be driven simultaneously with
DPWM2 or independently from DPWM2.
Pin 3: GATE1
This is the driver output for the gate of boost NMOS
switch for channel 1. The GATE = HIGH voltage is
equal to VIN voltage. It is recommended to add a 1
resistor between this pin and the NMOS gate. The
resistor value can be optimized depending on the
selection of NMOS switch. To reduce system noise
and input ripple current, GATE1 is 180out of phased
from GATE2.
Pins 4, 17: GND
These are the common ground for the IC controller. It
is recommended that all the low current paths are
connected to these pins as close as possible to the IC
controller. It is not recommended to connect any
output or input filter capacitors and any current sense
resistors to these pins directly. The IC controller
ground should be an island around the IC connected
to the PWR GND at a single point in the layout.
Pin 5: COMP1
This is for feedback loop compensation for Channel 1.
It is the output of the error amplifier that controls PWM
logic for the boost controller. An RC network should
be connected to GND to generate the compensation
for boost 1 feedback loop.
Pin 6: OVP1
This is the input for LED Over-Voltage Protection.
OVP1 monitors Channel 1 LED output voltage through
a resistor divider. When the voltage at this pin is
higher than 1V, Channel 1 will immediately stop
switching for 40ms and Pin 20 (FLAG) is instantly
asserted HIGH, indicating a Fault condition, CH1
controller will reset and restart again after 40ms. If
fault condition persists it will repeat until fault condition
is removed.
Pin 7: DBRT1
This is the input for digital brightness control for CH1.
A PWM logic signal is applied to this pin to vary the
brightness of the LED. The brightness of the LED is
proportional to the duty cycle of the PWM logic signal.
The input signal will control the output driver at
DPWM1 pin. This input pin cannot be left floating.
Pin 8: CS1
This is the input for peak current sense for CH1. This
pin serves the functions of current feedback, peak
current limit detection and fault current detection. The
pin current limit is internally set to 0.4V for peak
current limit and 0.48V for fault current detection,
under fault current detection, CH2 controller will assert
FLAG, shutdown and reset every 40ms.
Pin 9: FB1
This is the feedback input for boost controller for CH1.
This pin should connect to a resistor that senses the
LED current. The FB1 voltage will be regulated to Pin
10 (ISET) voltage. If the voltage at FB1 pin exceeds
1V due to a fault condition CH1 controller will reset
and start again after 40ms, if fault condition persists it
will repeat until fault condition is removed.
Pin 10: ISET
This is 0.5V output of the internal reference voltage of
the error Amp for both CH1 and CH2. This pin is
bidirectional; if desired it can be driven externally to
track an external reference or also can be used as a
linear dimming input from 0V to 0.8V, a 10nF or higher
value capacitor to GND must be connected to this pin.
Pin 11: SCP
Short Circuit Protection pin, the rising threshold at this
Pin is 1.14V and falling threshold is 0.96V, if the pin
voltage falls below 0.96V, FLAG will be asserted
HIGH and both channels will shut down and reset
every 40ms, if no current sense resistor this pin can
be used as a typical UVLO pin.
Rev. 1.0 January 2012
www.aosmd.com
Page 4 of 4

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AOZ1978 전자부품, 판매, 대치품
AOZ1978
Absolute Maximum Ratings
Exceeding the Absolute Maximum Ratings may damage the
device.
Parameter
VIN to GND
GATE1, DPWM1, GATE2,
DPWM2 to GND
COMP1, OVP1, DBRT1, CS1,
FB1, ISET COMP2, OVP2,
DBRT2, CS2, FB2, SCP, FLAG
to GND
Storage Temperature (TS)
ESD Rating(1)
Rating
-0.3V to +20V
-0.3V to +20V
-0.3V to +6V
-65°C to +150°C
2kV
Note:
1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5kin series with 100pF.
Recommended Operating Ratings
This device is not guaranteed to operate beyond the
Recommended Operating Ratings.
Parameter
Supply Voltage (VVIN)
Ambient Temperature (TA)
Package Thermal Resistance
SOIC-20 (JA)
Rating
8V to 18V
-40°C to +85°C
105°C/W
Electrical Characteristics
TA = 25°C, VIN = 12V unless otherwise specified. Specifications in BOLD indicate an ambient temperature range of
-40°C to +85°C.
Symbol Parameter
VVIN
IVIN_ON
VUVLO_RISE
VUVLO_FALL
VVIN_HYS
VIN Supply Voltage
VIN Quiescent Current
VIN UVLO Threshold
VIN UVLO Hysteresis
Oscillator
FSW Switching Frequency
TON Minimum ON Time (PWM)
GATE1 and GATE2 Driver
IGATE_SOURCE
IGATE_SINK
Source Current
Sink Current
TGATE_RISE Rise Time
TGATE_FALL
Inputs
IISET
ICS
ISCP
IDBRT
IOVP
IFB
FDBRT
Outputs
ISETVOUT
ISETSRC
IFLAG_SINK
Fall Time
ISET Input Current
CS Input Current
SCP Current
DBRT Input Current
OVP Input Current
FB Input Current
DBRT Dimming Frequency
ISET Output Voltage
ISET Output Source Current
FLAG Output Sink Current
Conditions
VIN rising
VIN falling
GATE1 or GATE2 = 0V
GATE1 or GATE2 = 12V
CGATE = 1nF
10% to 90% of VIN
CGATE = 1nF
90% to 10% of VIN
ISET = 0.6V
CS1 or CS2 = 0.3V
SCP = 1.2V
DBRT1 or DBRT2 = 5V
OVP1 or OVP2 = 1.2V
FB1 or FB2 = 0.5V
DBRT1 or DBRT2 duty cycle
from 1% to 99%
0.5V
ISET = GND
FLAG = 0.5V
Min.
8
6.2
170
350
600
Typ.
7
6.5
500
200
150
50
25
Max
18
2
7.3
230
200
85
45
Units
V
mA
V
mV
kHz
ns
mA
mA
ns
ns
5 µA
5 µA
5 µA
5 µA
5 µA
5 µA
100
2000
Hz
488 500 512 mV
10 µA
1 mA
Rev. 1.0 January 2012
www.aosmd.com
Page 7 of 7

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