ds3988 Maxim Integrated Products, Inc., ds3988 Datasheet
ds3988
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ds3988 Summary of contents
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... The DS3988 is an 8-channel controller for cold-cathode fluorescent lamps (CCFLs) used to backlight liquid crystal displays (LCDs and PC monitor applica- tions. The DS3988 supports configurations lamps, and multiple DS3988 controllers can be cascad support applications requiring more than 8 lamps. ...
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Cold-Cathode Fluorescent Lamp Controller ABSOLUTE MAXIMUM RATINGS Voltage SDA, and SCL CC Relative to Ground.............................................-0.5V to +6.0V Voltage on Leads Other than SDA, and SCL…………………………..-0. Stresses beyond those listed under “Absolute ...
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ELECTRICAL CHARACTERISTICS (continued +4.5V to +5.5V -40°C to +85°C PARAMETER SYMBOL High-Level Output Voltage (GA, GB) UVLO Threshold—V Rising CC UVLO Threshold—V Falling CC UVLO Hysteresis V SVM Threshold SVM Hysteresis LCM and OVD ...
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... Note 3: Voltage with respect to V DCB . Note 4: This is the minimum pulse width guaranteed to generate an output burst, which will generate the DS3988’s minimum burst duty cycle. This duty cycle may be greater than the duty cycle of the PSYNC input. Once the duty cycle of the PSYNC input is greater than the DS3988’ ...
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T = +25°C, unless otherwise noted ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE f = 71kHz LF:OSC 19 DPWM = 100% GATE Q = 3.5nC DPWM = 50% 13 DPWM = 10% 11 ...
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Cold-Cathode Fluorescent Lamp Controller (V = +5.0V +25°C, unless otherwise noted BURST DIMMING AT 150Hz AND 50% 1ms 5. 1ms 5. 1ms 2.0V LCM 1ms 2.0V OVD LAMP STRIKE WITH OPEN ...
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... PSYNC 43 configured as a DPWM receiver. If the DS3988 is configured as a DPWM source (i.e., the DPWM signal is generated internally), the DPWM signal is output on this pin for use by other DPWM receiver DS3988s. DPWM Oscillator Resistor Adjust. A resistor to ground on this lead sets the frequency of the DPWM oscillator (dimming clock) ...
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... EXTERNAL RESISTOR POSC DPWM FREQUENCY SET/ DPWM CLOCK INPUT 22.5Hz TO 440Hz OSCILLATOR (±5%) 8 _____________________________________________________________________ EEPROM CONTROL REGISTERS C- 8-BYTE USER MEMORY ENABLE/POR DS3988 CHANNEL FAULT FAULT HANDLING CHANNEL ENABLE 40kHz TO 80kHz x512 8-PHASE LFSS BIT AT PLL GENERATOR CR1.2 40kHz TO 80kHz OSCILLATOR (±5%) [20 ...
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... TO 40.96MHz] PHASED LAMP FREQUENCY [40kHz TO 80kHz] Figure 1. Per Channel Logic Diagram Detailed Description The DS3988 uses a push-pull drive scheme to convert a DC voltage (5V to 24V) to the high-voltage (600V to 1200V ) AC waveform that is required to power RMS the CCFLs. The push-pull drive scheme uses a minimal ...
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... DPWM signal. The DS3988 can generate its own DPWM signal internally (set DPSS = 0 in CR1), which can then be sourced to other DS3988s if required, or the DPWM signal can be supplied from an external source (set DPSS = 1 in CR1 ...
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... LFSS = 1 in CR1). When the lamp clock is internally generated, the frequency (40kHz to 80kHz) is set by an external resistor at the LOSC. In this case, the DS3988 can act as a lamp frequency source because the lamp clock is output at the LSYNC I/O pin for synchronizing any other DS3988s configured as lamp frequency receivers ...
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... BRIGHT PSYNC LSYNC POSC LOSC Figure 5. Frequency Configuration Options for Designs Using Multiple DS3988s Configuring Systems with Multiple DS3988s The source and receiver options for the lamp frequency clock and DPWM signal allow multiple DS3988s to be synchronized in systems requiring more than 8 lamps. ...
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... A 16 LAMP CYCLE PERIOD RESULTS IN A LINEAR RAMP IN LAMP CURRENT. LAMP CURRENT Figure 6. Digital PWM Dimming and Soft-Start At the beginning of each lamp burst, the DS3988 pro- vides a soft-start that slowly increases the MOSFET gate-driver duty cycle (see Figure 6). This minimizes the possibility of audible transformer noise that could result from current surges in the transformer primary ...
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... POSCR1 bit settings as shown in the Control Register 2 (CR2) table 4 in the Detailed Register Descriptions section. Example: Selecting the resistor values to configure a DS3988 to have a 50kHz lamp frequency and a 160Hz dimming clock frequency: For this configuration, POSCR0 and POSCR1 must be programmed to 1 and 0, respectively, to select 90Hz to 220Hz as the dimming clock frequency range ...
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... Figure 8 shows a flowchart of how the DS3988 controls and monitors each lamp. The steps are as follows: 1) Supply Check—The lamps will not turn on unless the DS3988 supply voltage is ≥4.5V and the voltage at the supply voltage monitor (SVM) input is ≥2V. 2) Strike Lamp—When both the DS3988 and the DC ...
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... Figure 6) at the begin- ning of each DPWM burst. Table 2 shows the duty cycles that correspond to each code. Selecting the Most Recent Value instructs the DS3988 to use the MOSFET duty cycle that was used for the last lamp cycle of the previous burst. ...
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Table 3. Control Register 1 (CR1) BIT NAME FUNCTION Lamp Overcurrent Lamp overcurrent detection disabled. 0 LOC 1 = Lamp overcurrent detection enabled. Note: Gate duty cycle changes during soft-start larger than 5% can cause false LOC fault. ...
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Cold-Cathode Fluorescent Lamp Controller Table 4. Control Register 2 (CR2) BIT NAME User Memory Write Protect. 0 UMWP 0 = User Memory Write Access Blocked 1 = User Memory Write Access Permitted DPWM Oscillator Range Select. When using an ...
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The following terminology is commonly used to 2 describe I C data transfers. Master Device: The master device controls the slave devices on the bus. The master device generates SCL clock pulses, start, and stop conditions. Slave Devices: Slave devices ...
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... DS3988, which allows the next byte of data to be written as soon as the DS3988 is ready to receive the data. The alternative to acknowl- edge polling is to wait for a maximum period of t elapse before attempting to write again to the DS3988. ...
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... The transformer should be able to operate in the 40kHz 80kHz frequency range of the DS3988, and the turns ratio should be selected so the MOSFET drivers run at 28% to 35% duty cycle during steady state operation. The transformer must be able to withstand the high open-circuit voltage that will be used to strike the lamp. ...
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... TYP MAX UNITS 40 80 kHz 200 mΩ Ω 500 12 µH 185 mH 70 µH 500 RMS NOTES to r each i ts nor ati nt each i ts nor ati nt. and GND on DS3988. CC ...
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... Fluorescent Lamp Controller SUPPLY VOLTAGE (5V ±10 DUAL POWER R1 SVM MOSFET GAn DS3988 GBn OVDn LCMn C1 GND For the latest package outline information www.maxim-ic.com/DallasPackInfo. Printed USA is a registered trademark of Maxim Integrated Products, Inc. Typical Operating Circuit SUPPLY VOLTAGE (5V ± ...