SC623A LED Light Management Unit Charge Pump, 4 LEDs, 400mA Flash LED, and I2C Interface POWER MANAGEMENT Features Description The SC623A is a high efficiency charge pump LED driver using Semtech’s proprietary mAhXLifeTM technology. Performance is optimized for use in single-cell Li-ion battery applications. Input supply voltage range — 3.0V to 5.5V Charge pump modes — 1x, 1.5x and 2x Four programmable current sinks with 32 steps from 0.5mA to 25mA Flash LED — 400mA max in flash mode, 250mA max continuous for spotlight Charge pump frequency — 250kHz I2C compatible interface — up to 400kHz Backlight current accuracy ±1.5% typical Backlight current matching ±0.5% typical Programmable fade-in/fade-out for main backlight External flash control pin to sync with camera Optional 1s flash time out Automatic sleep mode (LEDs off ) — IQ = 100μA Low shutdown current — 0.1μA (typical) Ultra-thin package — 3mm x 3mm x 0.6mm Fully WEEE and RoHS compliant The charge pump provides backlight current in conjunction with four matched current sinks. It also can supply continuous or bursted current to a flash LED using the dedicated flash driver current sink. The load and supply conditions determine whether the charge pump operates in 1x, 1.5x, or 2x mode. An optional fading feature that gradually adjusts the backlight current is provided to simplify control software. A flash-timeout feature disables the flash if active for longer than 1 second. The SC623A uses an I2C compatible serial interface. The interface controls all functions of the device, including backlight and flash currents. The flash/spotlight output is triggered via either the I2C interface or a dedicated pin. Applications Cellular phone backlighting and flash PDA backlighting and flash Camera I/O and core power In sleep mode, the device reduces quiescent current to 100μA while continuing to monitor the serial interface. Total current reduces to 0.1μA in shutdown. Typical Application Circuit MAIN BACKLIGHT VIN VBAT CIN 2.2μF VOUT I2C Data SDA I2C Clock SCL Flash Control Enable Control SC623A FLEN FLASH COUT 4.7μF BL 1 BL 2 BL 3 BL 4 EN FL AGND PGND C1+ C1 2.2μF C1- C2+ C2C2 2.2μF US Patents: 6,504,422; 6,794,926 June 27, 2007 © 2007 Semtech Corporation 1 SC623A C2- VIN C1+ C2+ VOUT Ordering Information C1- Pin Configuration 20 19 18 17 16 1 TOP VIEW 15 NC 14 NC PGND 2 FL 3 13 NC BL1 4 12 EN BL2 5 11 SDA 6 7 8 9 10 BL3 BL4 AGND SCL FLEN T Device Package SC623AULTRT(1)(2) MLPQ-UT-20 3×3 SC623AEVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Available in lead-free package only. Device is WEEE and RoHS compliant. MLPQ-UT-20; 3x3, 20 LEAD θJA = 35°C/W Marking Information 623A yyww xxxx yyww = Date Code xxxx = Semtech Lot No. 2 SC623A Absolute Maximum Ratings Recommended Operating Conditions VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0 Ambient Temperature Range (°C) . . . . . . . . -40 < TA < +85 VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0 VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 < VIN < 5.5 C1+, C2+ (V) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to (VOUT + 0.3) VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 < VOUT < 5.25 Pin Voltage — All Other Pins (V) . . . . . . . . . -0.3 to (VIN + 0.3) Voltage Difference between any two LEDs (V) . . . . . . < 1.2 VOUT Short Circuit Duration . . . . . . . . . . . . . . . . Continuous ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Thermal Information Thermal Resistance, Junction to Ambient(2) (°C/W) . . . . 35 Maximum Junction Temperature (°C) . . . . . . . . . . . . . . +150 Storage Temperature Range (°C) . . . . . . . . . . . . -65 to +150 Peak IR Reflow Temperature (10s to 30s) (°C) . . . . . . . +260 Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. NOTES: (1) Tested according to JEDEC standard JESD22-A114-B. (2) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. Electrical Characteristics Unless otherwise noted, TA = +25°C for Typ, -40ºC to +85°C for Min and Max, TJ(MAX) = 125ºC, VIN = 3.0V to 4.2V, CIN= C1= C2= 2.2μF, COUT = 4.7μF (ESR = 0.03Ω), ΔVF ≤ 1.2V(1) Parameter Symbol Conditions IQ(OFF) Min Typ Max Units Shutdown, VIN = 4.2V 0.1 2 μA Sleep, EN = VIN 100 160 μA Charge pump in 1x mode, 4 backlights on 3.8 4.65 Charge pump in 1.5x mode, 4 backlights on 4.6 5.85 Charge pump in 2x mode, 4 backlights on 4.6 5.85 VOUT pin shorted to GND 300 mA 160 °C Supply Specifications Shutdown Current Total Quiescent Current IQ mA Fault Protection Output Short Circuit Current Limit Over-Temperature Flash Mode Safety Timer(2) IOUT(SC) TOTP tFL(MAX) Flash sink active 0.75 1.00 1.25 s 3 SC623A Electrical Characteristics (continued) Parameter Symbol Conditions Min Typ Max Units VOVP VOUT pin open circuit, VOUT = VOVP rising threshold 5.3 5.7 6.0 V VUVLO Decreasing VIN Fault Protection (continued) Charge Pump Over-Voltage Protection 2.4 V 300 mV Undervoltage Lockout VUVLO-HYS Charge Pump Electrical Specifications Maximum Total Output Current IOUT(MAX) VIN > 3.4V, sum of all active LED currents, VOUT(MAX) = 4.0V 500 Backlight Current Setting IBL Nominal setting for BL1 thru BL4 0.5 25 mA Flash Current Setting IFL Nominal setting for FL 50 400 mA Backlight Current Accuracy IBL_ACC VIN = 3.7V, IBL = 12mA, TA = 25°C -8 ±1.5 +8 % Backlight Current Matching IBL-BL VIN = 3.7V, IBL = 12mA(3) -3.5 ±0.5 +3.5 % Flash Current Accuracy IFL_ACC VIN = 3.7V, IFL = 400mA, TA = 25°C -15 +15 % 1x Mode to 1.5x Mode Falling Transition Voltage V TRANS1x IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V 3.27 V 1.5x Mode to 1x Mode Hysteresis VHYST1x IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V 250 mV 1.5x Mode to 2x Mode Falling Transition Voltage V TRANS1.5x IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4) 2.92 V 2x Mode to 1.5x Mode Hysteresis VHYST1.5x IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4) 300 mV Current Sink Off-State Leakage Current IBLn VIN = VBLn = 4.2V 0.1 fPUMP VIN = 3.2V 250 Pump Frequency mA 1 μA kHz Digital I/O Electrical Specifications (FLEN, EN) Input High Threshold VIH VIN = 5.5V Input Low Threshold VIL VIN = 3.0V Input High Current IIH VIN = 5.5V Input Low Current IIL VIN = 5.5V 1.6 V 0.4 V -1 +1 μA -1 +1 μA 4 SC623A Electrical Characteristics (continued) Parameter Symbol Conditions Min Typ Max Units 0.4 V I2C Interface Interface complies with slave mode I2C interface as described by Philips I2C specification version 2.1 dated January, 2000. VB-IL Digital Input Voltage 1.6 VB-IH SDA Output Low Level V IDIN (SDA) ≤ 3mA -0.2 0.4 V 0.2 μA Digital Input Current IB-IN Hysteresis of Schmitt Trigger Inputs VHYS 0.1 V Maximum Glitch Pulse Rejection tSP 50 ns I/O Pin Capacitance CIN 10 pF Clock Frequency fSCL 400 SCL Low Period(5) tLOW 1.3 μs SCL High Period(5) tHIGH 0.6 μs Data Hold Time(5) tHD_DAT 0 μs Data Setup Time(5) tSU_DAT 100 μs Setup Time for Repeated START Condition(5) tSU_STA 0.6 μs Hold Time for Repeated START Condition(5) tHD_STA 0.6 μs Setup Time for STOP Condition(5) tSU_STO 0.6 μs Bus-Free Time Between STOP and START(5) tBUF 1.3 μs Interface Start-up Time(5) tEN I2C Timing Bus Start-up Time After EN Pin is Pulled High 440 1 kHz ms Notes: (1) ΔVF is the voltage difference between any two LEDs. (2) Once tripped, flash output will remain disabled until FLEN pin is cycled or reset via serial interface. (3) Current matching equals ± [IBL(MAX) - IBL(MIN] / [IBL(MAX) + IBL(MIN)]. (4) Test voltage is VOUT = 4.0V — a relatively extreme LED voltage — to force a transition during test. Typically VOUT = 3.2V for white LEDs. (5) Guaranteed by design 5 SC623A Typical Characteristics Battery Current (4 LEDs) — 25mA Each 160 Battery Current (4 LEDs) — 12mA Each VOUT=3.66V, IOUT=100mA, 25°C 80 73 Battery Current (mA) Battery Current (mA) 150 140 130 120 66 59 52 110 100 4.2 4.0 3.8 3.6 VIN (V) 3.4 3.2 45 4.2 3.0 Backlight Efficiency (4 LEDs) — 25mA Each 100 100 % Efficiency % Efficiency 3.8 3.6 VIN (V) 3.4 3.2 3.0 VOUT=3.50V, IOUT=48mA, 25°C 90 80 70 80 70 60 60 50 4.2 4.0 3.8 3.6 VIN (V) 3.4 3.2 50 4.2 3.0 3.8 3.6 3.4 3.2 3.0 Backlight Efficiency (4 LEDs) — 5.0mA Each VOUT=3.33V, IOUT=20mA, 25°C 100 35 VOUT=3.33V, IOUT=20mA, 25°C % Efficiency 90 30 25 80 70 60 20 15 4.2 4.0 VIN (V) Battery Current (4 LEDs) — 5.0mA Each Battery Current (mA) 4.0 Backlight Efficiency (4 LEDs) — 12mA Each VOUT=3.66V, IOUT=100mA, 25°C 90 40 VOUT=3.50V, IOUT=48mA, 25°C 4.0 3.8 3.6 VIN (V) 3.4 3.2 3.0 50 4.2 4.0 3.8 3.6 VIN (V) 3.4 3.2 3.0 6 SC623A Typical Characteristics (continued) Flash Current — 300mA 390 Flash Current — 400mA VOUT=3.58V at 25°C 490 460 Flash Current (mA) Flash Current (mA) 360 VOUT=3.39V at 25°C 330 300 270 240 430 400 370 340 210 4.2 4.0 3.8 3.6 VIN (V) 3.4 3.2 310 4.2 3.0 Spotlight Current — 50mA 53 340 52 3.6 VIN (V) 3.4 3.2 3.0 VOUT=3.50V at 25°C 310 Spotlight Current (mA) Spotlight Current (mA) 3.8 Spotlight Current — 250mA VOUT=3.02V at 25°C 51 50 49 48 47 4.2 4.0 280 250 220 190 4.0 3.8 3.6 VIN (V) 3.4 3.2 3.0 160 4.2 4.0 3.8 3.6 VIN (V) 3.4 3.2 3.0 7 SC623A Typical Characteristics (continued) Output Short Circuit Current Limit Flash Mode Safety Timer VOUT=0V, VIN=4.2V, 25°C VOUT (1V/div) VIN=3.7V, 25°C VFLEN (5V/div) VOUT (2V/div) IOUT (100mA/div) IFL (200mA/div) Time (1ms/div) Time (200ms/div) Output Open Circuit Protection Flash Current Pulse IFL=400mA, VIN=3.7V, VOUT=3.7V, 25°C VIN=3.7V, 25°C VFLEN (5V/div) VBL1 (500mV/div) VOUT (2V/div) VOUT (2V/div) IBL1 (20mA/div) IFL (200mA/div) Time (200μs/div) Time (40ms/div) 8 SC623A Pin Descriptions Pin # Pin Name Pin Function 1 C2- 2 PGND 3 FL Current sink output for flash LED(s) 4 BL1 Current sink output for main backlight LED 1 — leave this pin open if unused 5 BL2 Current sink output for main backlight LED 2 — leave this pin open if unused 6 BL3 Current sink output for main backlight LED 3 — leave this pin open if unused 7 BL4 Current sink output for main backlight LED 4 — leave this pin open if unused 8 AGND 9 SCL I2C clock input pin 10 FLEN Control pin for flash LED(s) — high = ON, low = OFF 11 SDA I2C bi-directional data pin — used for read and write operations for all internal registers (refer to Register Map and I2C Interface sections) 12 EN Chip enable — active high — low state resets all registers (see register map table) 13 NC Unused pin — do not terminate 14 NC Unused pin — do not terminate 15 NC Unused pin — do not terminate 16 VOUT 17 C2+ Positive connection to bucket capacitor 2 — requires a 1μF capacitor connected to C2- 18 C1+ Positive connection to bucket capacitor 1 — requires a 1μF capacitor connected to C1- 19 VIN Battery voltage input — connect with a 2.2μF capacitor to PGND 20 C1- Negative connection to bucket capacitor 1 — requires a1μF capacitor connected to C1+ T THERMAL PAD Negative connection to bucket capacitor 2 — requires a 1μF capacitor connected to C2+ Ground pin for high current charge pump and Flash LED driver Analog ground pin — connect to ground and separate from PGND current Charge pump output — all LED anode pins should be connected to this pin — requires a 4.7μF capacitor to PGND Thermal pad for heatsinking purposes — connect to ground plane using multiple vias — not connected internally 9 SC623A Block Diagram VIN 19 EN 12 SDA 11 FLEN 10 SCL 9 NC VIN C1+ C1- C2+ C2- 18 20 17 1 mAhXLifeTM Fractional Charge Pump (1x, 1.5x, 2x) 16 VOUT 2 PGND 4 BL1 5 BL2 6 BL3 7 BL4 3 FL 15 NC 14 NC Oscillator I2 C Compatible Interface and Logic Control Current Setting DAC 13 Bandgap Reference AGND VOUT 8 10 SC623A Applications Information General Description This design is optimized for handheld applications supplied from a single Li-Ion cell and includes the following key features: • • • • A high efficiency fractional charge pump that supplies power to all LEDs Four matched current sinks that control LED backlighting current, with 0.5mA to 25mA per LED An LED flash output that provides up to 400mA of momentary current or up to 250mA of continuous spotlight current An I2C compatible interface that provides control of all device functions High Current Fractional Charge Pump The backlight and flash outputs are supported by a high efficiency, high current fractional charge pump output at the VOUT pin. The charge pump multiplies the input voltage by 1, 1.5, or 2 times. The charge pump switches at a fixed frequency of 250kHz in 1.5x and 2x modes and is disabled in 1x mode to save power and improve efficiency. The mode selection circuit automatically selects the 1x, 1.5x or 2x mode based on circuit conditions. Circuit conditions such as low input voltage, high output current, or high LED voltage place a higher demand on the charge pump output. A higher numerical mode may be needed momentarily to maintain regulation at the VOUT pin during intervals of high demand, such as the high current of an LED flash or the droop at the VIN pin during a supply voltage transient. The charge pump responds to these momentary high demands, setting the charge pump to the optimum mode (1x, 1.5x or 2x), as needed to deliver the output voltage and load current while optimizing efficiency. Hysteresis is provided to prevent mode toggling. The charge pump requires two bucket capacitors for low ripple operation. One capacitor must be connected between the C1+ and C1- pins and the other must be connected between the C2+ and C2- pins as shown in the typical application circuit diagram. These capacitors should be equal in value, with a minimum capacitance of 2.2μF to support the charge pump current requirements. The device also requires a 2.2μF capacitor on the VIN pin and a 4.7μF capacitor on the VOUT pin to minimize noise and support the output drive requirements. Capacitors with X7R or X5R ceramic dielectric are strongly recommended for their low ESR and superior temperature and voltage characteristics. Y5V capacitors should not be used as their temperature coefficients make them unsuitable for this application. LED Backlight Current Sinks The backlight current is set via the I2C compatible interface. The current is regulated to one of 32 values between 0.5mA and 25mA. The step size varies depending upon the current setting. Between 0.5mA and 12mA, the step size is 0.5mA. The step size increases to 1mA for settings between 12mA and 15mA and 2mA for settings greater than 15mA. This feature allows finer adjustment for dimming functions in the low current setting range and coarse adjustment at higher current settings where small current changes are not visibly noticeable in LED brightness. All backlight current sinks have matched currents, even when there is variation in the forward voltages (ΔVF ) of the LEDs. A ΔVF of 1.2V is supported when the input voltage is at 3.0V. Higher ΔVF LED mis-match is supported when VIN is higher than 3.0V. All current sink outputs are compared and the lowest output is used for setting the voltage regulation at the VOUT pin. This is done to ensure that sufficient bias exists for all LEDs, including the flash LED. The backlight LEDs default to the off state upon powerup. For backlight applications using less than four LEDs, any unused output must be left open and the unused LED driver must remain disabled. When writing to the Backlight Enable Control register, a zero (0) must be written to the corresponding bit of any unused output. 11 SC623A Applications Information (continued) Backlight Quiescent Current The quiescent current required to operate all four backlights is reduced by 1.5mA when backlight current is set to 4.0mA or less. This feature results in higher efficiency under light-load conditions. Further reduction in quiescent current will result from using fewer than four LEDs. timer may be reset by either forcing the FLEN pin low or by resetting the Flash/Spotlight control bits via the interface. Shutdown State The device is disabled when the EN pin is low. All registers are reset to default condition when EN is low. Fade-In and Fade-Out Sleep Mode Backlight brightness can be set to automatically fade-in when current is set to increase and fade-out when current is set to decrease. When enabled with a new current setting, the current will step through each incremental setting between the old and new values. The result is a visually smooth change in brightness with a rate of fade that can be set to 8, 16, 24, or 32 ms per step. When all LEDs are off, sleep mode is activated. This is a reduced current mode that helps minimize overall current consumption by turning off the clock and the charge pump while continuing to monitor the serial interface for commands. LED Flash and Spotlight Current Sink A single output current sink is provided to drive both flash and spotlight functions. In flash mode, this current sink provides up to 400mA for a flash LED or array of parallel LEDs. Flash current settings are in 50mA increments from 50mA to 400mA. The FLEN pin directly triggers the FLASH function when pulled high, or it can be wired to VIN to enable software control via the serial interface. In spotlight mode, the output can be set for up to 250mA of continuous current. Settings are available in 50mA increments from 50mA to 250mA. Continuous operation above 250mA is not recommended due to high power dissipation. Flash and Spotlight Safety Timer A safety timer disables the flash and spotlight output current sink if the sink remains active for an extended period. The timer protects the SC623A and the LED from high power dissipation that can cause overheating. The timer’s default state is on, but the timer may be disabled via the serial interface to allow continuous output current in spotlight mode. The safety timer affects only the FL pin and will turn off the sink after a period of 1 second. The I2C Compatible Interface Functions All device functions can be controlled via the I2C compatible interface. The interface is described in detail in the Serial Interface section of the datasheet. Protection Features The SC623A provides several protection features to safeguard the device from catastrophic failures. These features include: • • • • Output Open Circuit Protection Over-Temperature Protection Charge Pump Output Current Limit LED Float Detection Output Open Circuit Protection Over-Voltage Protection (OVP) is provided at the VOUT pin to prevent the charge pump from producing an excessively high output voltage. In the event of an open circuit at VOUT, the charge pump runs in open loop and the voltage rises up to the OVP limit. OVP operation is hysteretic, meaning the charge pump will momentarily turn off until VOUT is sufficiently reduced. The maximum OVP threshold is 6.0V, allowing the use of a ceramic output capacitor rated at 6.3V with no fear of over-voltage damage. 12 SC623A Applications Information (continued) Over-Temperature Protection The Over-Temperature (OT) protection circuit helps prevent the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 160°C, the device goes into thermal shutdown with all outputs disabled until the junction temperature is reduced. All register information is retained during thermal shutdown. Charge Pump Output Current Limit The device also limits the charge pump current at the VOUT pin. When VOUT is shorted to ground, the typical output current is 300mA. The current limiting is triggered by an output under-voltage lockout below 2V. The output returns to normal when the short is removed and VOUT is above 2.5V. Above 2.5V, a typical current limit of 300mA applies when the FL current sink is off and a typical current limit of 1A applies when the FL current sink is on. LED Float Detection Float detect is a fault detection feature of the LED current sink outputs. If an output is programmed to be enabled and an open circuit fault occurs at any current sink output, that output will be disabled to prevent a sustained output OVP condition from occurring due to the resulting open loop. Float detect ensures device protection but does not ensure optimum performance. Unused LED outputs must be disabled to prevent an open circuit fault from occurring. 13 SC623A Applications Information (continued) • PCB Layout Considerations The layout diagram in Figure 1 illustrates a proper two-layer PCB layout for the SC623A and supporting components. Following fundamental layout rules is critical for achieving the performance specified in the Electrical Characteristics table. The following guidelines are recommended when developing a PCB layout: GND CIN C1 • VOUT VIN GND COUT C2 VOUT C1+ C2+ C1- Figure 2 — Layer 1 C2- NC PGND NC SC623A FL NC FLEN SDA SCL EN BL2 BL3 BL1 AGND • VIN • Place all bypass and decoupling capacitors — C1, C2, CIN, and COUT, as close to the device as possible. All charge pump current passes through VIN, VOUT, and the bucket capacitor connection pins. Ensure that all connections to these pins make use of wide traces so that the resistive drop on each connection is minimized. The thermal pad should be connected to the ground plane using multiple vias to ensure proper thermal connection for optimal heat transfer. BL4 • • Make all ground connections to a solid ground plane as shown in the example layout (Figure 3). If a ground layer is not feasible, the following groupings should be connected: PGND — CIN, COUT AGND — Ground Pad If no ground plane is available, PGND and AGND should be routed back to the negative battery terminal as separate signals using thick traces. Joining the two ground returns at the terminal prevents large pulsed return currents from mixing with the low-noise return currents. Figure 1 — Recommended PCB Layout Figure 3 — Layer 2 14 SC623A Register Map Address D7 D6 D5 D4 D3 D2 D1 D0 Reset Value Description 0x00 FADE_1 FADE_0 FADE_EN BL_4 BL_3 BL_2 BL_1 BL_0 0x00 Backlight Current Control 0x01 0(1) 0(1) 0(1) 0(1) BLEN_4 BLEN_3 BLEN_2 BLEN_1 0x00 Backlight Enable Control 0x02 0(1) 0(1) 0(1) FLTO FL_2 FL_1 FL_0 FL/SPLB 0x10 Flash/Spotlight Control Notes: (1) 0 = always write a 0 to these bits Register and Bit Definitions Backlight Current Control Register (0x00) This register is used to set the currents for the backlight current sinks, as well as to enable and set the fade step rate. These current sinks need to be enabled in the Backlight Enable Control register to be active. FADE[1:0] These bits are used to set the rise/fall rate between two backlight currents as follows: FADE_1 FADE_0 Fade Feature Rise/Fall Rate (ms/step) 0 0 32 0 1 24 1 0 16 1 1 8 during an ongoing fade operation, but an ongoing fade operation may be cancelled by resetting the fade bit. Clearing the fade bit during an ongoing fade operation changes the backlight current immediately to the value of BL[4:0]. The number of counts to complete a fade operation equals the difference between the old and new backlight values to increment or decrement the BL[4:0] bits. If the fade bit is cleared, the current level will change immediately without the fade delay. The rate of fade may be changed dynamically, even while a fade operation is active, by writing new values to the FADE_1 and FADE_0 bits. The total fade time is determined by the number of steps between old and new backlight values, multiplied by the rate of fade in ms/step. The longest elapsed time for a full scale fade-out of the backlight is nominally 1.024 seconds when the default interval of 32ms is used. The number of steps in changing the backlight current will be equal to the change in binary count of bits BL[4:0]. FADE_EN This bit is used to enable or disable the fade feature. When the fade function is enabled and a new backlight current is set, the backlight current will change from its current value to a new value set by bits BL[4:0] at a rate of 8ms to 32ms per step. A new backlight level cannot be written 15 SC623A Register and Bit Definitions (continued) BL[4:0] These bits are used to set the current for the backlight current sinks. All enabled backlight current sinks will sink the same current, as shown in Table 1. Table 1 — Backlight Current Control Bits BL_4 BL_3 BL_2 BL_1 BL_0 Backlight Current (mA) 0 0 0 0 0 0.5 0 0 0 0 1 1.0 0 0 0 1 0 1.5 0 0 0 1 1 2.0 0 0 1 0 0 2.5 0 0 1 0 1 3.0 0 0 1 1 0 3.5 0 0 1 1 1 4.0 0 1 0 0 0 4.5 0 1 0 0 1 5 0 1 0 1 0 5.5 0 1 0 1 1 6 0 1 1 0 0 6.5 0 1 1 0 1 7 0 1 1 1 0 7.5 0 1 1 1 1 8 1 0 0 0 0 8.5 1 0 0 0 1 9 1 0 0 1 0 9.5 1 0 0 1 1 10 1 0 1 0 0 10.5 1 0 1 0 1 11 1 0 1 1 0 11.5 1 0 1 1 1 12 1 1 0 0 0 13 1 1 0 0 1 14 1 1 0 1 0 15 1 1 0 1 1 17 1 1 1 0 0 19 1 1 1 0 1 21 1 1 1 1 0 23 1 1 1 1 1 25 BL Enable Control Register (0x01) This register is used to enable the backlight current sinks. BLEN[4:1] These bits are used to enable current sinks (active high, default low). BLEN_4 — Enable bit for backlight BL4 BLEN_3 — Enable bit for backlight BL3 BLEN_2 — Enable bit for backlight BL2 BLEN_1 — Enable bit for backlight BL1 When enabled, the current sinks will carry the current set by the backlight current control bits BL[4:0], as shown in Table 1. Flash/Spotlight Control Register (0x02) This register is used to configure the flash time-out feature, the flash or spotlight current, and select flash or spotlight current ranges. FLTO This bit is used to enable the flash safety time-out feature. The default state is enabled with FLTO = 1. If this bit is set, the device will turn off the flash after a nominal period of 1s. Two ways to re-enable the flash function after a safety time-out are: Pull the FLEN pin low to re-enable the flash function Clear and re-write FL[2:0] • • 16 SC623A Register and Bit Definitions (continued) FL[2:0] These bits are used to set the current for the flash current sink when configured for flash or spotlight by the FL/SPLB bit. Bits FL[2:0] set the flash or spotlight current, as shown in Table 2. Table 2 — Flash/Spotlight Control Bits FL_2 FL_1 FL_0 FL/ SPLB Flash/Spotlight Current (mA) 0 0 0 0 OFF 0 0 1 0 50 0 1 0 0 100 0 1 1 0 150 1 0 0 0 200 1 0 1 0 250 1 1 0 0 250 1 1 1 0 250 0 0 0 1 OFF 0 0 1 1 300(1) 0 1 0 1 350(1) 0 1 1 1 400(1) 1 0 0 1 400(1) 1 0 1 1 400(1) 1 1 0 1 400(1) 1 1 1 1 400(1) FL/SPLB This bit is used to select either the flash or spotlight current ranges. If this bit is set, the FL current sink can be used to drive a flash of maximum duration 500ms and the current range will be the high (flash) current range. If this bit is cleared, the FL current sink can be used to drive a continuous spotlight at a lower current and the current range will be the lower (spotlight) current range, as shown in Table 2. Note: (1) When on continuously, the device may reach the temperature limit with 300mA and higher. 17 SC623A Serial Interface The I2C General Specification 2 The SC623A is a read-write slave-mode I C device and complies with the Philips I2C standard Version 2.1, dated January 2000. The SC623A has four user-accessible internal 8-bit registers. The I2C interface has been designed for program flexibility, supporting direct format for write operation. Read operations are supported on both combined format and stop separated format. While there is no auto increment/decrement capability in the SC623A I2C logic, a tight software loop can be designed to randomly access the next register independent of which register you begin accessing. The start and stop commands frame the data-packet and the repeat start condition is allowed if necessary. SC623A Limitations to the I2C Specifications The SC623A only recognizes seven bit addressing. This means that ten bit addressing and CBUS communication are not compatible. The device can operate in either standard mode (100kbit/s) or fast mode (400kbit/s). Slave Address Assignment The seven bit slave address is 0110 111x. The eighth bit is the data direction bit. 0x6E is used for a write operation, and 0x6F is used for a read operation. Supported Formats The supported formats are described in the following subsections. Direct Format — Write The simplest format for an I2C write is direct format. After the start condition [S], the slave address is sent, followed by an eighth bit indicating a write. The SC623A I2C then acknowledges that it is being addressed, and the master responds with an 8 bit data byte consisting of the register address. The slave acknowledges and the master sends the appropriate 8 bit data byte. Once again the slave acknowledges and the master terminates the transfer with the stop condition [P]. Combined Format — Read After the start condition [S], the slave address is sent, followed by an eighth bit indicating a write. The SC623A I2C then acknowledges that it is being addressed, and the master responds with an 8 bit data byte consisting of the register address. The slave acknowledges and the master sends the repeated start condition [Sr]. Once again, the slave address is sent, followed by an eighth bit indicating a read. The slave responds with an acknowledge and the previously addressed 8 bit data byte; the master then sends a non-acknowledge (NACK). Finally, the master terminates the transfer with the stop condition [P]. Stop Separated Reads Stop-separated reads can also be used. This format allows a master to set up the register address pointer for a read and return to that slave at a later time to read the data. In this format the slave address followed by a write command are sent after a start [S] condition. The SC623A then acknowledges it is being addressed, and the master responds with the 8-bit register address. The master sends a stop or restart condition and may then address another slave. After performing other tasks, the master can send a start or restart condition to the SC623A with a read command. The device acknowledges this request and returns the data from the register location that had previously been set up. 18 SC623A Serial Interface (continued) I2C Direct Format Write S Slave Address W A Register Address S – Start Condition W – Write = ‘0’ A – Acknowledge (sent by slave) P – Stop condition A Data A P Slave Address – 7-bit Register address – 8-bit Data – 8-bit I2C Stop Separated Format Read Master Addresses other Slaves Register Address Setup Access S Slave Address W A Register Address A P S S – Start Condition W – Write = ‘0’ R – Read = ‘1’ A – Acknowledge (sent by slave) NAK – Non-Acknowledge (sent by master) Sr – Repeated Start condition P – Stop condition Slave Address B Register Read Access S/Sr Slave Address R A Data NACK P Data NACK P Slave Address – 7-bit Register address – 8-bit Data – 8-bit I2C Combined Format Read S Slave Address W A Register Address S – Start Condition W – Write = ‘0’ R – Read = ‘1’ A – Acknowledge (sent by slave) NAK – Non-Acknowledge (sent by master) Sr – Repeated Start condition P – Stop condition A Sr Slave Address R A Slave Address – 7-bit Register address – 8-bit Data – 8-bit 19 SC623A Outline Drawing — MLPQ-UT-20 3x3 A D PIN 1 INDICATOR (LASER MARK) DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX B E A2 A SEATING PLANE aaa C A A1 A2 b D D1 E E1 e L N aaa bbb .020 .000 - .024 .002 (.006) .006 .008 .010 .114 .118 .122 .061 .067 .071 .114 .118 .122 .061 .067 .071 .016 BSC .012 .016 .020 20 .003 .004 0.50 0.00 - 0.60 0.05 (0.1524) 0.15 0.20 0.25 2.90 3.00 3.10 1.55 1.70 1.80 2.90 3.00 3.10 1.55 1.70 1.80 0.40 BSC 0.30 0.40 0.50 20 0.08 0.10 C A1 D1 e LxN E/2 E1 2 1 N D/2 bxN bbb C A B NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS . 3. DAP is 1.90 x 190mm. 20 SC623A Land Pattern — MLPQ-UT-20 3x3 H R (C) DIMENSIONS K G Y X P Z DIM INCHES MILLIMETERS C G H K P R X Y Z (.114) (2.90) .083 .067 .067 .016 .004 .008 .031 .146 2.10 1.70 1.70 0.40 0.10 0.20 0.80 3.70 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com 21