MAX6948B MAXIM [Maxim Integrated Products], MAX6948B Datasheet
MAX6948B
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MAX6948B Summary of contents
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... The constant-current drivers contain programmable PWM outputs and allow staggering to reduce the input peak-current requirements. The I/O ports also feature ramp-up and ramp-down controls. The MAX6948B features a single input to select from four slave addresses. Programming and functionality for the five GPIO ports is identical to the MAX6946/MAX6947 I/O expanders ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports ABSOLUTE MAXIMUM RATINGS V+ to GND ...............................................................-0. COMP to GND ....................................-0.3V to (V+ + 0.3V) DD PGND to GND ......................................................-0.3V to +0. ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports ELECTRICAL CHARACTERISTICS (continued) (Typical Application Circuit 2.7V to 5.0V 3.3V 2.5V +25NC.) (Note PARAMETER SYMBOL Change ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports ELECTRICAL CHARACTERISTICS (continued) (Typical Application Circuit 2.7V to 5.0V 3.3V 2.5V +25NC.) (Note PARAMETER SYMBOL BOOST ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports TIMING CHARACTERISTICS (Typical Application Circuit 2.7V to 5.0V 3.3V 2.5V +25NC.) (Note PARAMETER SYMBOL Internal Boost-Converter ...
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... STANDBY CURRENT I vs. V+ RST 4 +105NC 3 +25NC 2 +85NC -40NC 1 0 5.00 2.70 3.16 3.62 4.08 V+ (V) SOFT-START V+, V OUT MAX6948B toc02 500mV/div V+ 5V/div V OUT SHUTDOWN RESPONSE (V+, V MAX6948B toc05 STANDBY CURRENT I 5.8 5.7 5.6 5.5 5.4 +25NC, +85NC, +105NC 5.3 5.2 4.54 5.00 2.70 3.16 3.62 4.08 V+ (V) (10/1024) MAX6948B toc03 OUT) MAX6948B toc06 500mV/div V+ 5V/div V OUT GND vs. V+ STBY -40NC 4.54 5.00 ...
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... ON, 10% PWM, FULL CURRENT AND HALF CURRENT) 7 -40NC, +25NC, +85NC, +105NC A 7.1 7.0 6.9 6.8 6.7 6.6 6.5 6.4 6.3 6.2 5.00 2.70 3.16 3.62 4.08 V+ (V) OUTPUT SINKING CURRENT vs. V PORT 40 FULL-CURRENT HALF-CURRENT PO FULL-CURRENT P2 10 HALF-CURRENT (V) PORT STAGGER PWM PORT WAVEFORMS vs. TIME ALL (50% PWM) MAX6948B toc17 1ms/div 4.54 5. ...
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... GPIO Port. Open-drain I/O. P4 can be configured as a 10mA (max) constant sink current output. E2 OUT Output Voltage Sense Input for Boost Converter E3 LEDSW High-Voltage, Constant-Current Input. Connect LEDSW to the cathode-end of the WLED string. E4 Inductor Switch Node 8 TOP VIEW (BUMP IN BOTTOM) MAX6948B RST SCL SDA ...
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... The constant-current drivers contain programmable PWM outputs and allow staggering to reduce the input peak current requirements. The I/O ports also feature ramp-up and ramp-down controls. The MAX6948B features a single input to select from four slave addresses. Programming and functionality for the five GPIO ports is identical to the MAX6946/MAX6947 I/O expanders ...
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... High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports Register Description The MAX6948B contains 25 internal registers (Table 1). Registers 0x00 to 0x15 control ports P0–P4 and remain compatible with the MAX6946/MAX6947 port expanders. Table 1. Register Address Map and Autoincrement Address ...
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... R/W 0x00 0x21 R/W 0x00 0x22 R/W 0x01 On power-up, all control registers are set to power- up values and the MAX6948B is in shutdown mode (Table 3). VALUE FUNCTION 1 Half-boost current set Full-boost current set RST does not change register data 1 RST resets registers to POR values ...
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... The LSB register (0x21) allows for very fine adjustments in LED intensity. The MAX6948B checks the boost converter and indi- cates its status in the boost-converter status register (Table 6). Faults indicated in this register include ther- mal shutdown, overvoltage, and current limit ...
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... Bit D0 of the boost-converter status register (0x22 bit D0 of the configuration register (0x10 (reset), and the device is in shutdown mode. The MAX6948B turns on and begins to quick-start after the junction temperature cools by 10NC. Reading this regis- ter causes the bit to reset. If the fault is still active, the bit Quick Start will be set again ...
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... Phasing section). Use registers 0x0A, 0x0B, and 0x0C to assign the same port setting to multiple ports (Table 1). When powered off, the I/O ports remain in high impedance. Figure 1 shows the I/O port structure of the MAX6948B. I/O ports P0–P4 default to high impedance on power-up, to prevent connected ports from drawing current. Ports used as inputs do not load their source signals ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports Ports Configured as Outputs The global-current register sets the full (maximum) constant-current sink amount for I/O ports configured as an output (Table 8). Power-up sets the global current ...
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... High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports PWM Intensity Control and Phasing The MAX6948B uses an internal 31.25kHz oscillator to generate PWM timing for LED intensity control. A PWM period comprises 256 cycles of the nominal 31.25kHz PWM clock (Figure 2). Each port can have an individual PWM duty cycle between 3/256 and 254/256 ...
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... The input port register returns logic 0 in the appropriate bit position for a port not configured as a logic input. The input ports’ registers are read only. The MAX6948B ignores writes to the input ports register. Standby Mode and Operating Current ...
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... This means that any ports used for GPIOs are still operational in shutdown mode. Put the MAX6948B into shutdown mode by setting the run bit (D0 the configuration register (0x10) (Table 2). Exit shutdown by setting the run bit high through the serial interface or by using the reset-run option (see the Reset-Run Option section) ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports FULL CURRENT/ HALF CURRENT Figure 4. Ramp-Up Behavior ZERO TO 4s HOLD-OFF DELAY BEFORE RAMP-DOWN FULL CURRENT/ HALF CURRENT 0 1/4s 1/2s 1s 1/8s 1/16s Figure 5. Hold-Off ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports Table 11. Port Ramp-Down Register Format (0x11) (continued) REGISTER DESCRIPTION 4.164s ramp-down from full current after ramp-down delay Zero ramp-down delay before fade-off 0.0655s ramp-down delay before fade-off ...
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... PWM clock. After enabling the reset-run option, the MAX6948B uses the rising edge on RST, followed ity to the MAX6948B for 128 to 129 periods of the GPIO PWM clock (32kHz typ) to trigger the reset-run option. If this timeout period elapses without the MAX6948B ...
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... Figure 9. START and STOP Conditions 22 Each transmission consists of a START condition (Figure 9) sent by a master, followed by the MAX6948B 7-bit slave address plus R/W bit, a register address byte more data bytes, and finally a STOP condition. Both SCL and SDA remain high when the interface is not busy ...
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... The bit following a 7-bit slave address is the R/W bit, which is low for a write command and high for a read command. Five bits (A6, A5, A4, A2, and A1), of the MAX6948B slave address are always and 0, respectively. Slave address bits A7 and A3 correspond, by the matrix in Table 13, to the states of the device address input AD0, and A0 corresponds to the R/W bit ...
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... R/W bit set to zero, followed by at least 1 byte of information. The first byte of infor- mation is the command byte. The command byte deter- mines which register of the MAX6948B written by the next byte, if received STOP condition is detected after the command byte is received, the MAX6948B takes no further action (Figure 13) beyond storing the command byte ...
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... The five I/O ports P0–P4 are overvoltage pro- × µ 0.5 s IN(MIN) tected to 5.5V independent × MAX6948B to operate from one supply voltage, such as 3.3V, while driving some of the five I/Os as inputs from a different logic level, such as 5V. L DCR (µH) (mω) 22 570 ...
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... High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports Driving LEDs into Brownout The MAX6948B correctly regulates the constant-current outputs, provided there is a minimum voltage drop across the port output. This port output voltage is the dif- ference between the load (typically LED) supply and the load voltage drop (LED forward voltage) ...
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... Keep traces short, direct, and wide. Keep noisy traces, such as the LX node trace, away from sensitive analog circuitry. For improved thermal per- formance, maximize copper area of the LX and PGND traces. Refer to the MAX6948B EV kit data sheet for an example layout. oper- DD ...
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High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports Chip Information PROCESS: BiCMOS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. ...