当前位置：文档库 › LED背光控制IC-OZ9998AGN资料

LED背光控制IC-OZ9998AGN资料

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

Change Summary

CHANGES

No. Applicable Section(s) Description Page(s) 1. All Assigned OZ9998A to LAMB8HP

All

2. Absolute Maximum Ratings

Added ISW rating. Updated

ISEN1/2/3/4/5/6/7/8 rating. 3 3. Recommended Operating Range

Added ISW rating. Updated

ISEN1/2/3/4/5/6/7/8 rating.

3 4. Electrical Characteristics

Updated limit for LED Short Circuit

Protection Threshold

5 5. Functional Description

Updated LED Short Circuit Protection

Threshold

REVISION HISTORY

Revision No.

Revision Summary

Release Date

0.50 Initial Release 10/16/2009 0.51 Update

11/17/2009

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

LED Backlight Controller

FEATURES

? High power DC-DC boost converter

controller

? Integrated LED current balance control

circuit

? Wide input voltage range

? Drives up to 8 strings in parallel ? User defined string selection ? External PWM dimming control

? Time-shift PWM phase dimming control for

low audible noise

? Multi-chip parallel operation for more than 8

LED strings

? MOSFET over-current protection ? LED short circuit protection ? LED open string protection ? Over-temperature protection ? Status output ? Low standby current

ORDERING INFORMATION

Part Number Temp Range Package

OZ9998ALN -20o

C to +85o

C Note 2, Page 3 24 pin QFN Lead-Free OZ9998AILN -40o C to +85o C Note 2, Page 3 24 pin QFN Lead-Free OZ9998AGN -20o C to +85o C Note 2, Page 3 24 pin SOP Lead-Free OZ9998ARN -20o

C to +85o

C Note 2, Page 3

24-pin E-TSSOP Lead-Free

GENERAL DESCRIPTION

OZ9998A is a high efficiency DC-DC controller that drives up to eight strings connected in parallel configuration with multiple LEDs in each string connected in series.

OZ9998A provides eight (8) LED current sense inputs in an “OR” configuration to improve backlight reliability. This allows the backlight to remain functioning in the event that a string(s) is damaged during normal operation

OZ9998A supports external Pulse Width Modulation (PWM) dimming control. The IC

provides the user with a variety of protection features.

The IC provides an integrated circuit to balance the current flow through each LED string. It also features a low standby current for the LED backlight system.

PIN DIAGRAM: 24QFN

I S E N 41

G N D A

I S E N 5

I S E N 6

I S E N 7

OVP

7ISET

8RT

9ENA

10ISW

11L D R

V R E F

G N D P 15

V I N

C O M P

STATUS

20PWM

21ISEN1

22ISEN2

23ISEN324PAD 25I S E N 8

SSTCMP

S E L 17

TYPICAL OPERATING CIRCUIT USING 24QFN

GND

ENA

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

PIN DESCRIPTION

Names Pin No 24QFN Pin No 24SOP Pin No 24E-TSSOP I/O

Description

ISEN4 1 5 5 I/O LED Current Sense 4 GNDA 2 6 6 --- Signal Ground ISEN5 3 15 10 I/O LED Current Sense 5 ISEN6

I/O

LED Current Sense 6

ISEN7 5 9 8 I/O

LED Current Sense 7 ISEN8 6 7 9 I/O LED Current Sense 8 OVP 7 10 11 I Over-Voltage Protection ISET 8 11 12 I/O LED Current Resistor Setting

RT 9 12 13 I/O Operation Frequency Resistor Setting ENA 10 13 14 I ON/OFF Control

ISW

I/O

Power MOSFET Current Sense

NC 12 23 23 --- LDR 13 16 16 I/O Low Side Power MOSFET Driver VREF

I/O

5V Regulator Supply For Low Voltage Blocks

GNDP 15 18 18 --- Power Ground VIN

---

IC Power Supply

SEL 17 20 20 I

Selection Setting To Set 2, 3 or 4 LED Channels COMP 18 21 21 I/O Multi-Chip Parallel Operation SSTCMP

22 I/O

Soft Start and Control Loop Compensation STATUS 20 24 24 O LED Operation Status Output PWM 21 1 1 I PWM Dimming Input ISEN1 22 2 2 I/O LED Current Sense 1 ISEN2 23 3 3 I/O LED Current Sense 2 ISEN3

I/O

LED Current Sense 3

Note 1: I=Input, O=Output, I/O=Input/Output

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

ABSOLUTE MAXIMUM RATINGS 2

Input Voltage 40.0V

GNDA, GNDP

+/- 0.3V

ISEN1/2/3/4/5/6/7/8 -0.3V to 60.0V ISW

-0.3V to 50.0V VREF, STATUS, OVP, PWM, ENA

-0.3V to 7.0V

ISET, SSTCMP, COMP, RT, SEL, LDR -0.3V to (VREF + 0.3V)

OZ9998ALN

OZ9998AGN

OZ9998ARN

Storage Temperature -55o C to 150o C

-55o C to 150o C

Operating Junction

Temperature (3)

150 o C 150 o C 150 o C ISEN1-8 LED Current 100mA

100mA

RECOMMENDED OPERATING RANGE

OZ9998ALN 4 OZ9998AGN 4

OZ9998ARN 4

VIN – Input Voltage 4.5V – 33.0V 4.5V – 33.0V 4.5V – 33.0V Operating Temperature

(3)

-20o C to +85o C -40o C to +85o C

-20o C to +85o C

Maximum Operating Junction

Temperature

125 o C 125 o C

125 o C ISEN1-8 LED Current 10mA to 80mA 10mA to 60mA 10mA to 80mA

ISEN1/2/3/4/5/6/7/8 ≤50.0V ≤50.0V ≤50.0V ISW ≤40.0V ≤40.0V ≤40.0V VREF, STATUS, OVP, PWM,

ENA

0.0V to 5.5V 0.0V to 5.5V

0.0V to 5.5V ISET, SSTCMP, COMP, RT,

SEL, LDR

0.0V to VREF 0.0V to VREF

0.0V to VREF Operating Frequency 100kHz - 1MHz 100kHz – 1MHz 100kHz - 1MHz PWM Frequency 100Hz – 20kHz 100Hz – 20kHz 100Hz – 20kHz R RT 21k ? to 100K ? 21k ? to 100K ? 21k ? to 100K ?

Thermal Impedance 3,4

θJ-C

θJ-A

24 pin QFN

5,6

5o C/W

38o C/W

24 pin SOP 13o C/W 86o C/W

24 pin E-TSSOP

7,8

15o C/W 38o C/W

Note 2

: The “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed and may cause permanent damage to the IC. These are stress ratings only and functional operation of the device at these or any other condition beyond those indicated in the Electrical Characteristics section of the specification is not implied. The “Electrical Characteristics” table defines the conditions for actual device operation. Exposure to absolute maximum rated conditions for extended periods may affect device reliability.

Note 3

: Not to exceed the maximum junction temperature of the IC, which relates to the operating power of the IC and the thermal resistance of the IC/package as above. For a typical application (refer to the Reference Application Circuit, Figure 3, page 10), the operation power of the IC can be calculated by Pd = Vin x Iin+V ISEN_1 x I ISEN_1 +…+V ISEN_8 x I ISEN_8 , where

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

? Using OZ9998A in an application circuit with an ambient temperature near 85o

C, the recommended power dissipation is approximately 526mW for the 24 pin QFN package, approximately 233mW for the 24 pin SOP package and approximately 526mW for the 24 pin E-TSSOP package.

It is recommended that the customer contact their local O2Micro Field Application Engineer (FAE), if the application is significantly different from the Reference Application Circuit illustrated in Figure 3, Page 10.

Note 4: Still air, low effective thermal conductivity board per JESD51-3.

Note 5: QFN bottom pad is recommended to be connected to ground.

Note 6

: QFN θJ-A under 50% and 0% bottom pad soldered condition is 43o

C/W and 72o

C/W respectively. The data was

based on simulation results using a 4 Layer, 76.2 x 114.3 mm 2

Printed Circuit Board (PCB). Note 7

: E-TSSOP bottom pad is recommended to be connected to ground.

Note 8

: E-TSSOP θJ-A under 50% and 0% bottom pad soldered condition is 43o

C/W and 72o

C/W respectively. The data

was based on simulation results using a 4 Layer, 76.2 x 114.3 mm 2

Printed Circuit Board (PCB).

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

ELECTRICAL CHARACTERISTICS 9

All specifications below are at T=25°C, VIN=24V; R RT =100k ? unless otherwise noted

LIMITS

PARAMETER CONDITIONS MIN TYP MAX

UNITS

VIN Operating Current ENA= PWM = 5V 10 mA VIN Shutdown Current ENA= PWM= 0V 2 5 μA VIN Stand-By Current

ENA=5V, PWM=0V

200

μA

Enable

High 2.4 - - ENA and PWM Logic

Low - 0.7 V

Under Voltage Lockout

Lockout Threshold VREF Lockout 3.6 V Resume Threshold

VREF Resume

3.8

Reference

VREF, VIN>6V 5.0 V Reference Voltage

Thermal Coefficient

ppm/°C VREF Output Current Capability

I VREF

30 mA

Drive Logic

LDR Sink Resistance VIN>6V 3.5 ? LDR Source Resistance VIN>6V

5 ? Minimum MOSFET ON Time 50 ns Minimum MOSFET OFF Time

Regulation

Regulation LED Current per Channel ISET=12Kohm 50 mA

LED Current Balance Rate

? - - +/-1.5 %

Protection

LED Open String Protection Threshold OVP

2.0

Shutdown Under Abnormal Condition

OVP 3.0 V

LED Short Circuit Protection Threshold ISEN1---8 7.0 V

Oscillator

R RT =100 K ? 500 kHz

Operation Frequency

Temp Coefficient

ppm/°C

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

ELECTRICAL CHARACTERISTICS 9

All specifications below are at T=25°C, VIN=24V; R RT =100k ? unless otherwise noted

LIMITS

PARAMETER CONDITIONS MIN TYP MAX

UNITS

Status Output

Sink Resistance

STATUS

100 ?

MOSFET Over-Current Protection

N-FET Over-Current Protection

ISW

0.5

Note 9

: Use of this product outside the limits of the test conditions may experience in a variation of parameters from the published parameters. If additional information is needed, please consult with your O2Micro Field Application Engineer (FAE).

Note 10

: %100**2)(/min max avg

I I I ??+=?

PARAMETERS GUARANTEED BY DESIGN 11

LIMITS

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

VREF

Load Regulation - 5 - mV / mA Line Regulation

0.3

mV / V

Thermal Protection

Lockout Temperature 140 °C Resume Temperature

110 °C Note 11

: Parameters Not Tested

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

FUNCTIONAL BLOCK DIAGRAM

Figure 1

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

FUNCTIONAL DESCRIPTION

Refer to the Functional Block Diagram in Figure 1, Page 7.

The Reference block provides the reference voltage, bias current and low voltage supply to the other internal blocks.

The HFOSC (High-Frequency Oscillator) block generates a constant frequency for OZ9998A operation.

The LED Current Balance block circuitry compensates the current variation among the 8-strings of LEDs and selects the lowest feedback current value for the normal operation of the system.

The Drive block provides the drive signals to drive an external N-Channel MOSFET. The N-Channel MOSFET current is detected at pin ISW and performs the current mode control.

The Protection block provides the circuitry for various protection features. Refer to Section 7, Page 9 for more information.

Refer to the Typical Application Circuit in Figure 3, Page 10 for the operation of the DC/DC converter.

1. Enable

OZ9998A is enabled when the voltage to ENA is greater than approximately 2.4V. A voltage of less than approximately 0.7V disables the IC.

An under-voltage lockout protection feature is provided and will disable the IC. When the voltage at VIN decreases, thus forcing the voltage at VREF to drop to approximately 3.6V, the IC output is disabled. The IC will resume normal operation once the voltage at VIN increases the voltage at VREF to a threshold of approximately 3.8V. VREF has a maximum external source capability of 30mA.

2. High Frequency Oscillator

The user-defined constant operation frequency is set by external resistor R28 connected to RT. Resistor R28 sets the charging current for the internal oscillator. The approximate operating frequency can be calculated by the following equation.

fop [MHz] = -------------- R RT [k ?]

3. LED String Selection

The following is a guideline to set the number of active strings.

? ISEN1~8 Active: SEL = GNDA ? ISEN1~6 Active: SEL = VREF ? ISEN1~4 Active: SEL = NC

4. Setting and Regulation of LED Current

Once the operating frequency is selected, the next step is to determine the LED current. The LED current is determined by the following equation:

600

I LED [mA] = -------------- R ISET [k ?]

This setting is the reference for the LED current at pins ISEN1-8 and represents the sensed LED current for each string. The DC-DC converter regulates the LED current according to the setting. During normal operation, the minimum current among the 8 strings, ISEN1-8, is controlled and determines the current for all other strings.

5. External PWM Dimming

External PWM dimming is set by applying a signal of 100Hz to 20kHz to pin PWM. Varying the PWM duty cycle from 0% to 100% controls the panel brightness from minimum to maximum brightness respectively.

To reduce audible noise and ripple stresses, OZ9998A provides a time-shift PWM phase dimming feature. Referring to Figure 2, Page 9, every two ISEN rising and falling edges are phase-shifted by one drive (LDR) operation period.

The minimum “on/off” time of the LED strings is approximately two operation periods of the drive (LDR) output.

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

ISEN7/8 currents

1 switching period

Figure 2

If the voltage at pin PWM is less than approximately 0.7V (logic low) for a period of approximately 20,000 drive (LDR) periods, the IC will be disabled and will enter standby mode. For example, 20,000 drive periods equates to 20ms at a 1MHz switching frequency. Once the voltage at PWM pin is greater than approximately 2.4V, the IC will resume normal operation. Therefore, the turn on/off sequence of PWM and ENA is free.

6. Multi-Chip Parallel Operation

For applications using more than 8 strings, several OZ9998A ICs can be implemented and share a single power train. Refer to Figure 4, Page 11.

When using more than 1 OZ9998A IC, the COMP pin for each IC must be shorted together. The external N-MOSFET drive signal for the multi chip application is controlled by the LDR pin on the Master IC. The setting for the Slave IC(s) is the same as the Master, except for the following:

? LDR pin is floating

? ISW pin is shorted to GNDA

? OVP setting is ~10% lower than Master

7. Protection Features

A. MOSFET Over-Current Protection

OZ9998A monitors the MOSFET drain current and provides an over-current protection. During the MOSFET turn-on period, when the voltage on ISW rises above approximately 0.5V, the drive output, LDR, will shut “off”. The drive output will turn “on” when the next cycle begins. until the voltage at pin OVP reaches an approximate 2.0V threshold. The IC will automatically ignore the open string(s) and the remaining string(s) will continue operation.

If all the strings are open and the voltage at OVP reaches a threshold of approximately 2.0V, the MOSFET drive output (LDR) will turn ”off” and the IC will shut down and latch.

D. Output Short-circuit to ground/ Open Schottky Diode Protection

When OVP pin voltage is less than ~0.1V, MOSFET drive output (LDR) will turn off. This protects the converter from damage if the output schottky diode (D1) is open (defective or poor solder contact), or Vout is shorted to ground.

E. Over-Temperature Protection

If IC temperature is higher than 140°C, all blocks, with the exception of the Reference block, are turned “off”. The IC resumes normal operation when temperature falls below 110°C.

F. Shutdown Under Abnormal Condition

When the voltage at pin OVP is greater than approximately 3.0V, the IC will shut down and latch. Toggle ENA to restart the IC. This feature can be used for any other protection feature to shut down the IC, by pulling up OVP above approximately 3.0V, if the protection condition is satisfied.

G. Status Output

After the IC is enabled, STATUS will output a logic low if any of the following conditions exists:

1) Any string is open

2) LED short circuit protection 3) Over voltage protection

4) Over temperature protection

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

REFERENCE APPLICATION CIRCUIT USING 24 PIN QFN

PWM1

VOUT

Figure 4: Application Circuit Using 2-OZ9998A Driving 16 LED Strings

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

PACKAGE INFORMATION – 24-PIN SOP: OZ9998AGN (300 mil)

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

PACKAGE INFORMATION– 24 PIN E-TSSOP (173mil): OZ9998ARN

C o n t r o l l e d R e c i p i e n t #137395 p r i n t e d o n 3/9/2010. U p d a t e s w i l l b e p r o v i d e d t o r e g i s t e r e d r e c i p i e n t s .

IMPORTANT NOTICE

No portion of O 2Micro specifications/datasheets or any of its subparts may be reproduced in any form, or by any means, without prior written permission from O 2Micro.

O 2Micro and its subsidiaries reserve the right to make changes to their datasheets and/or products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability.

O 2Micro warrants performance of its products to the specifications applicable at the time of sale in accordance with O 2Micro’s standard warranty. Testing and other quality control techniques are utilized to the extent O 2Micro deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.

Customer acknowledges that O 2Micro products are not designed, manufactured or intended for incorporation into any systems or products intended for use in connection with life support or other hazardous activities or environments in which the failure of the O 2Micro products could lead to death, bodily injury, or property or environmental damage (“High Risk Activities”). O 2Micro hereby disclaims all warranties, and O 2Micro will have no liability to Customer or any third party, relating to the use of O 2Micro products in connection with any High Risk Activities.

Any support, assistance, recommendation or information (collectively, “Support”) that O 2Micro may provide to you (including, without limitation, regarding the design, development or debugging of your circuit board or other application) is provided “AS IS.” O 2Micro does not make, and hereby disclaims, any warranties regarding any such Support, including, without limitation, any warranties of merchantability or fitness for a particular purpose, and any warranty that such Support will be accurate or error free or that your circuit board or other application will be operational or functional. O 2Micro will have no liability to you under any legal theory in connection with your use of or reliance on such Support.