SC618ULTRT

SC618 SEMTECH | Alldatasheet

Document overview

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Technical content

Features

Flash and spotlight — two selectable modes Flash mode — up to 700mA output Flash mode — 500mA max output (over rated voltage, temperature, and load conditions) Flash mode safety timer shut-off — 1 second Spotlight mode set to 40% of fl ash current Spotlight mode — up to 280mA output Spotlight mode —1x mode (under most conditions) for best efficiency Input range — 3.0V to 5.25V External fl ash control pin for synchronization to a cam- era module or graphics controller Short-circuit, over-voltage, and over-temperature pro- tection Soft-start functionality Separate fl ash and spotlight control inputs for maxi- mum versatility Ultra-thin package MLPD-UT-10 — 3mm x 3mm x 0.6mm

Applications

PDAs with built-in cameras

Description

The SC618 is a high-current charge pump designed spe- cifically for use with white LEDs used in camera flash applications. Only two small bucket capacitors are required to develop the output drive, providing a low EMI solution compared to inductive boost regulators. The SC618 has two modes of operation: fl ash mode and spotlight mode. In fl ash mode, the SC618 is capable of delivering 500mA of regulated current for a duration of 500ms or up to 700mA for a reduced duration. A safety timer is also included to ensure the LED cannot be left on indefi nitely and overheat. In spotlight mode the SC618 outputs 40% of the fl ash mode current and can remain enabled continuously. An external resistor is connected in series with the LED to set the current. In fl ash mode, this resistor can dissipate up to 175mW, reducing the power dissipation require- ment of the SC618. The fl ash input overrides the control input to make sure the fl ash function is activated . The SC618 ultra-thin package provides both a low profi le and high thermal effi ciency. SC618 VIN C2- C2+ C1- C1+ VOUT FLASH CTRL GND ISET 1μF 1μF FLASH CTRL 1μF RSET 10μF VBAT White LED Typical Application Circuit August 2, 2007

Ordering Information

SC618ULTRT(1)(2) MLPD-UT-10 3×3 SC618EVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Lead-free package only. Device is WEEE and RoHS compliant. TOP VIEW T

10 C2+1VIN

9 VOUT

8 C1+

7 CTRL

6 ISET

MLPD-UT-10; 3x3, 10 LEAD θJA = 49°C/W yyww = Date code xxxx = Semtech Lot Number

Exceeding the above specifi cations may result in permanent damage to the device or device malfunction. Operation outside of the parameters specifi ed 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. Absolute Maximum Ratings OUT + 0.3) Recommended Operating Conditions Thermal Information Thermal Resistance, Junction to Ambient(2) (°C/W) . . . . 49 Parameter Symbol Conditions Min Typ Max Units Output Current IOUT FLASH high, RSET = 0.357Ω 3.7V < VIN < 4.2V, VOUT = 3.7V(1) 700 mA FLASH high, RSET = 0.5Ω 3.3V < VIN < 4.2V 2.8V < VOUT < 4.25V 460 500 540 FLASH low, CTRL high, RSET = 0.357Ω 3.7V < VIN < 4.2V, VOUT = 3.4V(1) 280 FLASH low, CTRL high, RSET = 0.5Ω 3.0V < VIN < 4.5V 2.8V < VOUT < 4.5V 170 200 230 ISET Reference Voltage VISET FLASH high, RSET = 0.5Ω 3.3V < VIN < 4.2V 2.8V < VOUT < 4.25V 230 250 270 mV FLASH low, CTRL high, RSET = 0.5Ω 3.0V < VIN < 4.5V 2.8V < VOUT < 4.5V 85 100 115 Quiescent Current I Q FLASH high 3.4 5.0 mA FLASH low, CTRL high 2.0 4.5 mA FLASH low, CTRL low 0.1 2.0 μA

Electrical Characteristics

Parameter Symbol Conditions Min Typ Max Units Flash Mode Pulse Duration(2) tFLASH 3.3V < VIN < 4.2V IOUT = 500mA, VOUT > 2.8V 500 ms Flash Mode Start-Up Time(2) tF-SU t = 0 when FLASH goes high to IOUT = 90% of fi nal value 1m s Flash Mode Safety Timer(2) tSAFE FLASH high 0.90 1.25 s Spotlight Mode Start-Up Time(2,3) tS-SU VIN = 4.2V, VOUT = 3.2V; t = 0 when CTRL goes high to IOUT = 90% of fi nal value 1m s Oscillator Frequency f OSC Device enabled 250 kHz Oscillator Frequency Accuracy ΔfOSC -15 15 % Short-Circuit Output Current Limit ISC Steady State with VOUT shorted to GND 600 mA Input Current Limit I LIMIT 2x mode, 3.3V < VIN < 4.2V 1.0 2.1 A 2x mode, VIN = 3.7V, VOUT = 3.7V, TA = 25°C 1.38 1.53 Over-Temperature Protection(2) TOT Rising threshold 150 TOT -HYS Hysteresis 10 Logic Input High Threshold V IH FLASH, CTRL 1.5 V Logic Input Low Threshold V IL FLASH, CTRL 0.4 V Logic Input High Current I IH FLASH 1 20 35 μA CTRL 2 40 70 Logic Input Low Current I IL FLASH, CTRL 0.1 2.0 μA ISET Ripple Voltage V ISET(P-P) Spotlight mode — IOUT = 200mA 25 mV FLASH mode — IOUT = 500mA 100 Electrical Characteristics (continued) Notes: 1) V OUT required by the typical LED at this current. 2) Guaranteed by design - not tested in production. 3) If conditions force 2x mode operation, this start-up time will increase by approximately 32ms due to the timer that is enabl ed to ensure 2x mode is needed.

Flash Current at 10ms, RISET = 500mΩ, VOUT = 3.75V 485 490 495 500 505 510 515 VIN (V) LED Current (mA) Flash Current at 500ms, RISET = 500mΩ, VOUT = 3.58V 485 490 495 500 505 510 515 VIN (V) LED Current (mA) Spotlight Current, RISET = 500mΩ, VOUT = 3.16V 180 188 196 204 212 220 VIN (V) LED Current (mA) 1x Mode Transition to 2x Mode Flash Duration, RISET = 500mΩ, VOUT = 3.75V (start), 3.58V (LED Heated 500ms) 485 491 497 503 509 515 0 100 200 300 400 500 Pulse Duration (ms) LED Current (mA) VIN=4.2VVIN=3.7V VIN=3.3V Flash Duration, RISET = 350mΩ, VOUT = 3.86V (start), 3.61V (LED Heated 500ms) 675 695 715 735 755 0 100 200 300 400 500 Pulse Duration (ms) LED Current (mA) VIN=4.2V VIN=3.7V VIN=3.3V VIN=3.4V Flash Current at 100ms, RISET = 500mΩ, VOUT = 3.68V 485 490 495 500 505 510 515 VIN (V) LED Current (mA)

Typical Characteristics (continued) Flash Mode Ripple, RISET = 500mΩ Time (200ms/div) Safety Timer Shut-Off Time (40μs/div) Start-Up Flash Mode, 500mA Ch 1: 100mV/DIV Ch 2: 200mV/DIV Ch 3: 200mV/DIV Time (4μs/div) Ch 1: 100mV/DIV Ch 2: 2V/DIV Ch 3: 2V/DIV Ch1: 100mV/DIV Ch2: 2V/DIV Ch3: 5V/DIV Spotlight 1x Mode Ripple, RISET = 500mΩ Time (4μs/div) Ch1: 50mV/DIV Ch2: 50mV/DIV Ch3: 50mV/DIV Short Circuit Current Limiting, VIN = 5.25V, VOUT = 0V Time (400ms/div) Ch1: 2V/DIV Ch4: 100mA/DIV Spotlight 2x Mode Ripple, RISET = 500mΩ Time (4μs/div) Ch1: 50 mV/DIV Ch2: 100 mV/DIV Ch3: 100 mV/DIV

Pin# Pin Name Pin Function

1 VIN Input voltage

2 C2- Negative terminal of bucket capacitor 2

3 GND Ground— connect to ground plane using multiple vias

4 C1- Negative terminal of bucket capacitor 1

5 FLASH Flash mode enable pin— puts the device in active fl ash mode when high and also overrides CTRL. 6 ISET Current-setting reference pin — connect to the LED cathode and the current setting resistor. 7 CTRL Control input bit — used to enable and set the output current in spotlight mode when high.

8 C1+ Positive terminal of bucket capacitor 1

9 VOUT Output pin — connect to the LED anode

10 C2+ Positive terminal of bucket capacitor 2

T Thermal Pad Pad for heat sinking purposes — not connected internally. Connect to ground plane using multiple vias.

The SC618 is a powerful dual-mode charge pump designed to drive a high-intensity white LED. A constant current spotlight mode or a pulsed current with higher intensity is used for camera fl ash. The device operates in 2x mode while operating in fl ash mode. In spotlight mode it can operate in either 2x or 1x mode depending on the load current, load voltage, and input voltage levels. In fl ash mode the SC618 output can drive 500mA at 4.25V into an LED for a minimum duration of 500ms under all temperature and input conditions. The FLASH pin is used to trigger this mode (active high). In spotlight mode the SC618 regulates the output current to 40% of the fl ash mode current setting, when the CTRL pin is pulled high and the FLASH pin is low. Flash mode has priority over spotlight mode, i.e., the FLASH pin triggers fl ash mode regardless of the state of the CTRL pin. Output current is regulated by attaching the ISET pin to the cathode(s) of the LED package and a low resistance sense resistor (typically 0.5Ω). The ISET pin monitors the voltage at the cathode and signals the charge pump to increase or decrease the output current until the ISET voltage reaches the programmed setting. The resistor value is chosen to set the current through the LED based on this reference voltage. The resistor can be chosen to set either the flash mode current or spotlight mode current, but it should not be less than 0.35Ω due to output current limitations of the device. Flash Mode Flash mode is enabled whenever the FLASH pin is pulled high and remains active until the FLASH pin is released. This mode has higher priority than spotlight mode, so the state of the CTRL pin is overridden whenever the FLASH pin is activated. While in fl ash mode the reference voltage on the ISET pin is set to 250mV. The duration of the pulse is limited by the amount of power that can be dissipated in the SC618 before it exceeds the maximum operating temperature. If an output current less than the rated 500mA is desired, the duration of the pulse can increase proportionally. Extending fl ash mode beyond the 500ms pulse limit could adversely affect the long term reliability of the SC618. Flash duration must be derated at higher currents. For example, 700mA derates to a maximum of 350ms. In fl ash mode, I OUT = 250mV/RISET. Figure 1 shows maximum fl ash mode current for extended duration times. 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 900 1000 Flash Duration [ms] Flash Current [mA] Figure 1 — Maximum Flash Duration Flash Mode Safety Timer The SC618 provides a time-out protection function when in fl ash mode. The output is disabled if the FLASH pin is held high for longer than 1 second to protect the LED. Once this time-out has occurred, the output will stay dis- abled until the FLASH pin has been pulled low and then re-enabled. Spotlight Mode Spotlight mode is enabled by setting the CTRL pin high and keeping the FLASH pin low. When in spotlight mode, the SC618 can maintain a constant current indefi nitely to drive an LED or bank of LEDs. The ISET reference voltage is set to 100mV so that the output current is maintained at 200mA when a 0.5Ω resistor is used. Spotlight current is always 40% of fl ash current for any given value of R ISET. In spotlight mode, IOUT = 100mV/RISET. To maximize power efficiency, the SC618 has been designed to operate in 1x mode when conditions do not require the charge pump to be active. When fi rst enabled the SC618 attempts to regulate the voltage on the ISET pin in 1x mode. If the voltage on the ISET pin cannot be maintained and this condition persists for longer than 32ms, then the charge pump will change to 2x mode operation. In a typical application, the SC618 will operate in 1x mode until the supply voltage decreases suffi ciently Applications Information

Applications Information (continued) that the voltage on the ISET pin can no longer be main- tained. After a 32ms delay (included to prevent false transitions) the charge pump will convert to 2x mode. After the charge pump switches from 1x mode to 2x mode, the device remains in 2x mode until the part is turned off . If the part is re-enabled in spotlight mode, it will begin operation in 1x mode and determine the appropriate mode of operation as previously described. Protection Circuitry The SC618 provides several protection features to safe- guard the device from catastrophic failures. These features include: Input Over-Voltage Protection (IOVP) Output Over-Voltage Protection (OVP) Over-Temperature Protection (OTP) Over-Current Protection (OCP) Short-Circuit Current Protection (SCCP) Input Over-Voltage Protection IOVP is included to prevent operation at high input volt- ages that could damage the device. The IOVP circuit senses the input voltage and determines when the supply exceeds 6V. Hysteresis is included in this circuit to avoid chattering between states. When the voltage rises above this threshold, the device is disabled until the input voltage drops to a level within the specifi ed range. Output Over-Voltage Protection Output OVP prevents the SC618 from generating an output voltage that could damage other devices con- nected to it such as load LEDs and bypass capacitors. When the output voltage exceeds 5.5V, the OVP circuit disables the charge pump until the voltage decreases to a level within the acceptable range. This circuit allows the device to drive LEDs with high forward voltages at a reduced level without exceeding the output voltage limits specifi ed for the device. Over-Temperature Protection The OTP circuit prevents the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 150°C the device is disabled. It remains disabled until the junction temperature drops below this threshold. Hysteresis is included to prevent toggling between modes. Over-Current Protection When the SC618 is in 2x mode, the input current will be approximately double the required output. When the steady-state load requires the maximum current avail- able in 2x mode, the OCP circuit prevents the device from overheating from excessive power dissipation. This feature protects the device when in 1x mode. The current limit is set lower in the 1x mode due to lower current requirements. Short-Circuit Current Protection SSCP is provided to limit the current that can be sourced when the output is shorted to ground. When a short circuit forces V OUT to drop below 2V, the SCCP detects the condition and limits the output current. Resistor Selection The ISET resistor selection is critical in generating the correct current. The value can be chosen to set the spot- light mode current or the fl ash mode current, and the two current settings are dependent on the same resistor. It is recommended that the resistor be selected to match the desired LED current for fl ash mode. This allows the designer to set the SC618’s maximum current and select the resistor package size necessary for the power dissi- pation required in fl ash mode. The typical application uses a 0.5Ω resistor to set a fl ash mode current of 500mA and spotlight mode current of 200mA. A high precision resistor should be used to ensure the specifi ed accuracy for LED current. To avoid malfunction of the charge pump, it is recom- mended that the resistance seen at the ISET pin remain constant while the device is active (flash or spotlight mode). Changing the resistance value or the load current while the device is active could cause instability. Capacitor Selection The SC618 is designed to use low-ESR ceramic capacitors for the input and output bypass capacitors as well as the charge pump bucket capacitors. Ideal performance is achieved when C1 is exactly equal to C2. It is recom- mended that X5R or X7R ceramic capacitors be used for best performance.

The following layout is suggested for a two-layer design. The capacitors C1 and C2 are the bucket capacitors and each conducts the full load current of up to 500mA pulsed for one half clock cycle. C3 is the output decoupling capacitor placed near the VOUT pin. C4 is the input decoupling capacitor placed near the VIN pin. Multiple vias should be used whenever it is necessary to change layers on nets connecting to pins VIN, VOUT, GND, C1-, C1+, C2- and C2+. The load current return path is from the ISET sense point through the resistor and back to the ground pins. Resistance in this path adds to the total resistance and has the eff ect of reducing the LED current by about 4% per 10mV of DC drop across the return copper trace in fl ash mode. For this reason, it is crucial to have a low resis- tance return path. Place and ground the resistor as close as possible to the ground pin of the SC618. The trace from the ISET pin has virtually no current. The ISET trace should make contact at the pad of the power sense resistor to minimize the effect of voltage drop between the LED cathode and the resistor. Resistor R1 is routed with a very low resistance connec- tion between R1 and GND pin 3. The sense trace between Pin 6 and R1 is routed around the ground vias, allowing the shortest ground return path possible. The sense trace is connected to R1 at the positive terminal pad for the most accurate output possible. The bottom copper layer is mostly a ground plane with no obstructions between the ground vias. The smaller rectangle to the left con- nects the input power to VIN pin 1 and input capacitor C4. The two traces at the lower left are for logic inputs FLASH and CTRL. The trace to the right is the ISET pin sense trace. The sense trace is routed out of the path of the returning ground current. Thermal Resistance Considerations The SC618 package is thermally effi cient when the circuit board layout connects the thermal pad through multiple vias to the ground plane. The thermal resistance is rated at 49°C/W, and this rating is dependent on the connec- tion between the thermal pad and the ground plane. The layout should keep the junction temperature below the OTP limit while operating the SC618 within the specifi ed electrical conditions for I OUT and VISET. A poor layout may allow the junction temperature to reach the OTP limit Applications Information (continued) while in fl ash or spotlight mode. It is critical to maintain adequate ground plane around the device to maximize heat transfer and avoid over-temperature shutdown.

(LASER MARK) INDICATOR PIN 1 N MIN aaa bbb b e L N D C E A DIM MILLIMETERS NOM DIMENSIONS MAXNOM INCHES MIN MAX NOTES: CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.2. .003 .007 .042 .009 .048 .000 .018 (.006) 0.08 0.23 .011 .052 0.18 1.06 .024 .002 0.00 0.45 1.31 0.30 1.21 0.05 0.60 (0.1524) .004 0.10 0.50 BSC.020 BSC aaa C SEATING PLANE A bbb C A B B e C E E C A2 LxN bxN D A Outline Drawing — MLPD-UT-10

Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com Contact Information SC618 Land Pattern — MLPD-UT-10 THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FUNCTIONAL PERFORMANCE OF THE DEVICE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR Y ZG(C) P .087 .055 2.20 1.40 .150 .020 .012 .037 3.80 0.30 0.95 0.50 (.112) .075 1.90 (2.85) K H X THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: INCHES DIMENSIONS G K H X Y P Z C DIM MILLIMETERS