Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - lighting/front end device controller CCFL controller SSOP 20 Surface-mount

General Description

The MAX1739/MAX1839 fully integrated controllers are

optimized to drive cold-cathode fluorescent lamps

(CCFLs) using the industry-proven Royer oscillator

inverter architecture. The Royer architecture provides

near sinusoidal drive waveforms over the entire input

range to maximize the life of CCFLs. The MAX1739/

MAX1839 optimize this architecture to work over a wide

input voltage range, achieve high efficiency, and maxi-

mize the dimming range.

The MAX1739/MAX1839 monitor and limit the trans-

former center-tap voltage when required. This ensures

minimal voltage stress on the transformer, which

increases the operating life of the transformer and

eases its design requirements. These controllers also

provide protection against many other fault conditions,

including lamp-out and buck short faults.

These controllers achieve 50:1 dimming range by

simultaneously adjusting lamp current and “chopping”

the CCFL on and off using a digitally adjusted pulse-

width modulated (DPWM) method. CCFL brightness is

controlled by an analog voltage or is set with an

SMBus

-compatible two-wire interface (MAX1739).

The MAX1739/MAX1839 drive an external high-side

N-channel power MOSFET and two low-side N-channel

power MOSFETs, all synchronized to the Royer oscilla-

tor. An internal 5.3V linear regulator powers the MOS-

FET drivers and most of the internal circuitry. The

MAX1739/MAX1839 are available in space-saving

20-pin QSOP packages and operate over the -40°C to

+85°C temperature range.

________________________Applications

Notebook/Laptop Computers

Car Navigation Displays

LCD Monitors

Point-of-Sale Terminals

Portable Display Electronics

Features

♦ Fast Response to Input Change

♦ Wide Input Voltage Range (4.6V to 28V)

♦ High Power-to-Light Efficiency

♦ Minimizes Transformer Voltage Stress

♦ Lamp-Out Protection with 2s Timeout

♦ Buck Switch Short and Other Single-Point Fault

Protection

♦ Integrated Royer MOSFET Drivers Reduce

Transformer Pin Count

♦ Buck Operation Synchronized to Royer Oscillator

♦ Synchronizable DPWM Frequency

♦ Pin-Selectable Brightness Control Interface

♦ SMBus Serial Interface (MAX1739)

♦ Analog Interface (MAX1739/MAX1839)

MAX1739/MAX1839

†

Wide Brightness Range

CCFL Backlight Controllers

________________________________________________________________ Maxim Integrated Products 1

BATT

BSTCCV

CCI

MINDAC

REF

TOP VIEW

GND

DL1MODE

CTL/SCL

CRF/SDA

SH/SUS

DL2

SYNCCTFB

CSAV

MAX1739

QSOP

Pin Configuration

19-1755; Rev 1; 3/01

EVALUATION KIT

AVAILABLE

†

SMBus is a trademark of Intel Corp.

PART TEMP. RANGE PIN-PACKAGE

MAX1739EEP -40°C to +85°C 20 QSOP

MAX1839EEP -40°C to +85°C 20 QSOP

Ordering Information

Pin Configurations continued at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim's website at www.maxim-ic.com.

Summary of content (26 pages)

PAGE 1
9-1755; Rev 1; 3/01 KIT ATION EVALU E L B AVAILA Wide Brightness Range CCFL Backlight Controllers The MAX1739/MAX1839 fully integrated controllers are optimized to drive cold-cathode fluorescent lamps (CCFLs) using the industry-proven Royer oscillator inverter architecture. The Royer architecture provides near sinusoidal drive waveforms over the entire input range to maximize the life of CCFLs.
PAGE 2
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers ABSOLUTE MAXIMUM RATINGS VBATT to GND ...........................................................-0.3V to 30V VBST, VSYNC to GND.................................................-0.3V to 34V VBST to VLX .................................................................-0.3V to 6V VDH to VLX .................................................-0.3V to (VBST + 0.3V) VLX to GND...................................................-6V to (VBST + 0.
PAGE 3
Wide Brightness Range CCFL Backlight Controllers (V+ = 8.2V, V SH/SUS = V SH = 5.5V, MINDAC = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS DAC AND ERROR AMPLIFIER DAC Resolution Guaranteed monotonic MINDAC Input Voltage Range MINDAC Input Bias Current MINDAC Digital PWM Disable Threshold CSAV Input Voltage Range CSAV Regulation Point Bits 0 2 V 0 < VMINDAC < 2V -1 1 μA MINDAC = VL 2.4 4 V 0.8 V 2.
PAGE 4
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers ELECTRICAL CHARACTERISTICS (continued) (V+ = 8.2V, V SH/SUS = V SH = 5.5V, MINDAC = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNIT 5.5 V ANALOG INTERFACE BRIGHTNESS CONTROL (MODE connected to REF or GND ) CRF/SDA, CRF Input Range 2.7 20 µA VCRF/SDA = VCRF = 5.
PAGE 5
Wide Brightness Range CCFL Backlight Controllers (V+ = 8.2V, V SH/SUS = V SH = 5.5V, MINDAC = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 6) PARAMETER CONDITIONS MIN TYP MAX UNITS SUPPLY AND REFERENCE VBATT Input Voltage Range VL = VBATT 4.6 5.5 VL = open 6 28 VBATT Quiescent Current, Shutdown SH/SUS = SH = GND VL Output Voltage, Normal Operation 6V < VBATT < 28V, 0 < ILOAD < 15mA VL Undervoltage Lockout Threshold 5.0 VL rising (leaving lockout) V 20 µA 5.6 V 4.
PAGE 6
Typical Operating Characteristics (VIN = 12V, VCTL = VCRF, VMINDAC = 1V, MODE = GND, Circuit of Figure 8.) WIDE INPUT RANGE (VBATT = 20V) MAX1739/1839 toc02 MAX1739/1839 toc01 WIDE INPUT RANGE (VBATT = 8V) VCTAP 5V/div VCSAV 500mV/div VDH 20V/div VDH 20V/div WIDE INPUT RANGE (VBATT = 20V, DPWM = 9%, VCTL = 0) MAX1739/1839 toc04 WIDE INPUT RANGE (VBATT = 8V, DPWM = 9%, VCTL = 0) MAX1739/1839 toc03 4μs/div VCTAP 10V/div VCCV VCCV VCCV, VCCI 200mV/div VCCI VCCI VCCI VCCV VCCV 1.
PAGE 7
Wide Brightness Range CCFL Backlight Controllers (VIN = 12V, VCTL = VCRF, VMINDAC = 1V, MODE = GND, Circuit of Figure 8.
PAGE 8
Typical Operating Characteristics (continued) (VIN = 12V, VCTL = VCRF, VMINDAC = 1V, MODE = GND, Circuit of Figure 8.) VL vs. BATT VOLTAGE MAX1739/1839 toc13 4.6 6 4.5 5 NORMAL OPERATION 4.4 3 5.25 4.3 5.20 4.2 5.15 4.1 1 4.0 0 5.10 0.01 0.1 1 10 SHUTDOWN 4 VL (V) SHUTDOWN 5.30 SHUTDOWN VL (V) NORMAL OPERATION 5.35 2 0 100 5 10 15 20 VBATT (V) IVL (mA) VL vs. TEMPERATURE MAX1739/1839 toc15 5.36 4.60 5.35 4.55 5.34 4.50 NORMAL OPERATION 5.33 4.45 5.32 4.40 5.
PAGE 9
Wide Brightness Range CCFL Backlight Controllers PIN NAME FUNCTION MAX1739 MAX1839 1 REF REF 2V Reference Output. Bypass to GND with 0.1μF. Forced low during shutdown. 2 MINDAC MINDAC DAC Zero-Scale Input. VMINDAC sets the DAC’s minimum scale output voltage. Disable DPWM by connecting MINDAC to VL. 3 CCI CCI GMI Output. Output of the current loop GMI amplifier that regulates the CCFL current. Typically bypass to GND with 0.1μF . 4 CCV CCV GMV Output.
PAGE 10
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers Detailed Description detect. Figure 1 shows the current and voltage waveforms for the three operating modes with the brightness control set to 50% of full scale. The MAX1739/MAX1839 regulate the brightness of a CCFL in three ways: The MAX1739/MAX1839 include a 5.3V linear regulator to power most of the internal circuitry, drivers for the buck and Royer switches, and the synchronizable DPWM oscillator.
PAGE 11
Wide Brightness Range CCFL Backlight Controllers With MINDAC between REF and GND, DPWM is enabled and the MAX1739/MAX1839 begin pulsing the lamp current. During the on-cycle, VCCV is at 150mV above VCCI. After the on-cycle, VCCV is forced down to 1.2V to provide soft-start at the beginning of the next on-cycle. Also, VCCI retains its value until the beginning of the next on-cycle. When VCCV increases, it causes the buck regulator duty cycle to increase and provides soft-start.
PAGE 12
REF VL VL 0.6V SYNC CS CTFB CCV CCI CSAV MODE GND CTL/SCL CRF/SDA GMV GMI 500mV 450mV CCV CLAMP PK_DET_CLAMP SUPPLY BUCK ENABLE MINDAC = VL? Y = 1, N = 0 ROYER OSC BUCK REGULATOR PWM CONTROL PWM RAMP GENERATOR PEAK DETECTOR DPWM OSC SMBus LAMP CURRENT AND DPWM CONTROL CS CS DL2 DL1 LX DH BST REF SH/SUS VL BATT MINDAC REF MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers Figure 2.
PAGE 13
Wide Brightness Range CCFL Backlight Controllers Buck Regulator The buck regulator uses the signals from the PWM comparator, the current-limit detection on CS, and DPWM signals to control the high-side MOSFET duty cycle. The regulator uses voltage-mode PWM control and is synchronized to the Royer oscillator. A falling edge on SYNC turns on the high-side MOSFET after a 375ns minimum off-time delay. The PWM comparator or the CS current limit ends the on-cycle.
PAGE 14
brightness code of ob00000 corresponds to a 9.375% DPWM duty cycle, and a brightness code of ob11111 corresponds to a 100% DPWM duty cycle. The duty cycle changes by 3.125% per step, except codes ob00000 to ob00011 all produce 9.375% (Figure 3). To disable DPWM and always use 100% duty cycle, set VMINDAC to VL. Note that with DPWM disabled, the equations above should assume VMINDAC = 0 instead of VMINDAC = VL.
PAGE 15
Wide Brightness Range CCFL Backlight Controllers BRIGHTNESS POSITIVESCALE ADC NEGATIVESCALE ADC SMBus DAC OUTPUT DPWM DUTY CYCLE (%) COMBINED POWER LEVEL (%) Maximum Brightness MODE = GND, VCTL/SCL = VCRF/SDA MODE = REF, VCTL/SCL = 0 Bright [4:0] = ob11111 Full-scale DAC OUTPUT = 195.
PAGE 16
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers VL REF T1 ADC- L1 10k MODE LX MAX1739 MAX1839 MAX1739 MAX1839 SMBus ADC+ R14 SYNC 500pF GND DPWM SYNCHRONIZATION SIGNAL R15 REF R4 CTFB Figure 6. DPWM Synchronization GND R5 optimized using R14 and R15 as shown in Figure 7. The resistor-divider can be used to force commutation as close to the zero-crossing point as possible. POR and UVLO The MAX1739/MAX1839 include power-on reset (POR) and undervoltage lockout (UVLO) features.
PAGE 17
Wide Brightness Range CCFL Backlight Controllers Both buck-switch short and lamp-out detection will clear the STATUS1 bit in the SMBus interface. STATUS1 does not clear immediately but will clear about 2 seconds after the inverter has been forced off (see Digital Interface). Note that once the inverter board fuse has blown, SMBus communications with the part will cease since the MAX1739 will then be without power.
PAGE 18
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers a proven application that is useful for a wide range of CCFL tubes and power ranges. Table 5 shows the recommended components for a 4.5W application. MOSFETs The MAX1739/MAX1839 require three external switches to operate: N1, N2A, and N2B. N1 is the buck switch; select a logic-level N-channel MOSFET with low RDSON to minimize conduction losses (100mΩ, 30V typ). Also select a comparable-power Schottky diode for D1.
PAGE 19
Wide Brightness Range CCFL Backlight Controllers L1 VCT C6 CCFL N = NS/NP NS T1 NP NP D5A T1 TO CTFB MAX1739/MAX1839† VS = VS(RMS) = N ✕ 1.1 ✕ VCT R4 D5B N2A N2B CSAV IL, RMS, MAX = 0.04304 R13 R5 R13 2π ω -NπVCT 2 IL,PK IL,PK IR13, AVG IL,RMS ILAMP NπVCT 2 IR13 πVCT 2 T1 SECONDARY VOLTAGE (PIN 10–PIN 6) T1 PRIMARY-TAP VOLTAGE (PIN 2) VCT is the average DC voltage at center top -IL,PK 2π ω 2π ω 2π ω Figure 9. Transformer Primary/Secondary Voltage Relationship Figure 10.
PAGE 20
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers transient that CCCV is designed to protect against is open tube at the beginning of DPWM pulses. Large CCCV values reduce transient overshoots, but can cause loss of regulation at low DPWM duty cycles by increasing the delay to strike voltage. Smaller values of C CCV allow quicker DPWM startups and faster response to fault conditions.
PAGE 21
Wide Brightness Range CCFL Backlight Controllers MAX1739/MAX1839† Write-Byte Format S ADDRESS WR ACK COMMAND ACK DATA ACK 7 bits 1b 1b 8 bits 1b 8 bits 1b Slave Address Command Byte: selects which register you are writing to P Data Byte: data goes into the register set by the command byte Read-Byte Format S ADDRESS WR ACK COMMAND ACK 7 bits 1b 1b 8 bits 1b Slave Address Command Byte: selects which register you are reading from Send-Byte Format S S ADDRESS RD ACK DATA /
PAGE 22
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers A tLOW B tHIGH C E D F G I H J K L M SMBCLK SMBDATA tHD:STA tSU:STA tSU:DAT A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE LOW tHD:DAT tHD:DAT tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO MASTER K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION, DATA EXECUTED BY SLAVE M = NEW START CONDITION F = ACKNOWLEDGE BIT CLOCK
PAGE 23
Wide Brightness Range CCFL Backlight Controllers R OR W PROTOCOL DATA REGISTER BIT ASSIGNMENT COMMAND POR BYTE* STATE BIT 7 (MSB) BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 (LSB) Read and Write 0x01 0b0XXX XX01 0x17 0 0 0 BRIGHT4 (MSB) BRIGHT3 BRIGHT2 BRIGHT1 BRIGHT0 (LSB) Read and Write 0x02 0b0XXX XX10 0xF9 STATUS1 STATUS0 1 1 1 SHMD2 SHMD1 SHMD0 Read Only 0x03 0b0XXX XX11 0x96 ChipID7 1 ChipID6 0 ChipID5 0 ChipID4 1 ChipID3 0 ChipID2 1 ChipID1 1 ChipID0 0 Read On
PAGE 24
MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers Status Register [STATUS1–STATUS0] (POR = 0b11) The status register returns information on fault conditions. If a lamp is not connected to the secondary of the transformer, the MAX1739 will detect that the lamp current has not exceeded the CSAV detection threshold and after 2 seconds will clear the STATUS1 bit (see Lamp-Out Detection). The STATUS1 bit is latched; i.e., it will remain 0 even if the lamp-out condition goes away.
PAGE 25
Wide Brightness Range CCFL Backlight Controllers Chip Information TRANSISTOR COUNT: 7194 TOP VIEW REF 1 20 BATT MINDAC 2 19 DH CCI 3 18 LX CCV 4 SH 5 17 BST MAX1839 16 VL CRF 6 15 GND CTL 7 14 CS MODE 8 13 DL1 CSAV 9 12 DL2 CTFB 10 11 SYNC QSOP ______________________________________________________________________________________ 25 MAX1739/MAX1839† Pin Configurations (continued)
PAGE 26
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) QSOP.EPS MAX1739/MAX1839† Wide Brightness Range CCFL Backlight Controllers Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.