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PDF AOZ1977-1 Data sheet ( Hoja de datos )
| Número de pieza | AOZ1977-1 | |
| Descripción | High Voltage LED Driver IC | |
| Fabricantes | Alpha & Omega Semiconductors | |
| Logotipo |  |
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AOZ1977-1
High Voltage LED Driver IC
General Description
The AOZ1977-1 is a high-efficiency LED driver
controller for high voltage LED backlighting
applications. It is designed to drive high-brightness
LED light bar in LED TV applications. The AOZ1977-1
can support a wide range of input and output
voltages. The input bias voltage of AOZ1977-1 is
from 8V to 30V.
The AOZ1977-1 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.
Low feedback voltage (500mV) helps reduce power
loss.
The AOZ1977-1 features sync function to allow for
synchronization with external clock or multiple
AOZ1977-1.
The AOZ1977-1 is available in a standard SO-16
package and operates over the temperature range of
-40°C to +85°.
Features
• 8V to 30V input bias voltage
• Up to 16V driving capability at GATE pin and
DPWM pin.
• Disconnect control pin for PWM dimming or fault
conditions.
• Bi-directional Clock synchronization
• 500mV feedback regulation
• Feedback short protection
• 8 bit PWM dimming resolution
• Cycle-by-cycle current limit
• Output over-voltage protection
• LED short and open protection
• Thermal shutdown protection
• SO-16 package
Applications
• LCD TV LED backlight
• LED monitor
• General LED lighting
Typical Application
Rev. 1.0 November 2011
www.aosmd.com
Page 1 of 16
1 page  
Functional Block
AOZ1977-1
Absolute Maximum Ratings
Exceeding the Absolute Maximum Ratings may damage the
device.
Parameter
Rating
VIN to GND
-0.3V to +32V
GATE, FAULTB to GND
-0.3V to +16V
VDD to GND
PWMDIM, OSC, ISET, COMP,
FB TIMER, SYNC, CS. ILIM,
VREF, OVP, to GND
-0.3V to +16V
-0.3V to +6V
Storage Temperature (TS)
ESD Rating(1)
-65°C to +150°C
2kV
Note:
1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5kΩ in 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-16 (ΘJA)
Rating
8V to 30V
-40°C to +85°C
105°C/W
Rev. 1.0 November 2011
www.aosmd.com
Page 5 of 16
5 Page 
AOZ1977-1
Application Information
Inductor Selection
Inductor choice will be affected by many parameters,
like duty cycle based on input/output setting, switching
frequency, full scale LED current level, and mode of
operations. Boost controller can operate under
discontinuous mode, continuous mode, or critical
conduction mode. For high voltage boost LED driver
applications, it is recommended to use critical
conduction mode for good stability and best efficiency.
ILPEAK
Inductor Current in Critical Conduction Mode
Input _Current
= IIN
= VOUT ×I OUT
VIN
In critical conduction mode:
ILPEAK = di = 2 × IIN
The duty cycle for the boost DC/DC system is defined
as:
Duty _ Cycle = D = VOUT − VIN(MIN)
VOUT
To determine the ON time for the boost switch:
ON _ time = dt = D
FSW
For the application with VIN=100V, VOUT=200V, LED
current=200mA:
IIN
=
200V × 0.2A
90V
=
0.44A
di = 2 × 0.44A = 0.89A
D = 200V − 90V = 0.55
200V
The inductor value is determined by:
L = dt ×VIN = 5.5µs × 90V = 560µH
di 0.88A
After the inductor value is calculated, we need to
consider the DCR resistance and the Isat saturation
current of the inductor. Inductor DCR is inversely
proportional to the Isat. It is recommended to select
an inductor for which the Isat value should be at least
50% higher than the ILpeak value. To minimize EMI
effect, it is always preferable to use shielded type
inductors.
Diode Selection
It is recommended to use fast recovery diode for D1.
For most applications, Schottky diodes with correct
current and voltage rating are suitable. The diode
current rating should be at least higher than the full
scale LED current. The diode voltage rating should be
higher than the OVP level of VOUT voltage.
Output Capacitors
The amount and type of capacitor used is mainly
determined by the design output ripple (VRIPPLE)
requirement:
COUT
= IOUT
VRIPPLE
×D
FSW
When selecting output capacitors, it is more important
to check the effective ESR of the capacitor than the
actual capacitance value. For examples, a 10µF
capacitor with 0.02Ω ESR will handle higher ripple
current but produce less output ripple than a 33µF
capacitor with 0.04Ω ESR. It is recommended to use
low ESR MLCC ceramic capacitors. For high voltage
cost effective application, multiple Electrolytic
capacitors in parallel will reduce the total effective
ESR.
Input Capacitors
The input capacitors for boost converters do not
require low ESR due to the fact that the input current
is continuous. Also, they do not contain large peak
current as compared to the output capacitors.
The ripple current at the input capacitor is:
( )IIN _ RIPPLE
=
0.3 × VIN × VOUT − VIN
FSW × L × VOUT
= 0.17A
where,
FSW is the switching frequency, 100KHz in this
example.
Electrolytic capacitors should work well with the
appropriate voltage and ripple current rating, it is not
recommended to use Tantalum capacitors because
Boost converters do exhibit high surge currents during
startup which can cause tantalum capacitors to fail.
Rev. 1.0 November 2011
www.aosmd.com
Page 11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AOZ1977-1.PDF ] | |
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