Description Features The SE3362 is a charge pump operating in either ¾ Drives individually up to 4 LEDs 1x mode or 2x fractional mode regulating current ¾ Output current up to 30mA per LED through each of the 4 LED pins. Operation at a fixed ¾ Digital control On/Off of each LED high frequency of 1MHz typical allows the use of ¾ Compatible with supply voltage of 2.85V to 5.5V very small value ceramic capacitors. ¾ Power efficiency up to 90% The SE3362 drives white light-emitting diodes ¾ 2 modes of operation 1x and 2x (LED’s) connected in parallel and provides tightly ¾ Automatic short circuit detect/disable matched regulated current to achieve uniformity of ¾ High-frequency Operation at 1MHz brightness in LCD backlighting applications. An ¾ Low value ceramic capacitors external resistor RSET controls the output current ¾ Automatically switch to power save mode if no level. LED currents of up to 30mA are supported LED is deteted to be connected to the IC over a range of input supply voltages from 2.85V to ¾ Thin QFN 16-lead package, 3×3mm 5.5V, making the device ideal for battery-powered ¾ 100% Lead (Pb)-Free applications. LED dimming can be accomplished by several methods including using a resistor Rset (the exact Application formula will be provided in the Application ¾ Color LCD and keypad Backlighting Section) to set the RSET pin current, applying a ¾ Cellular Phones PWM signal on the Control signals, or adding a ¾ Handheld Devices switched resistor in parallel with Rset. The Enable ¾ Digital Cameras input pin allows the device to be placed in ¾ PDAs power-down mode with close to "zero” quiescent ¾ Portable MP3 players current. The SE3362 features short circuit and Over Temperature Protection (OTP). The device is available in a 16- lead thin QFN package with a max height of 0.8mm. Application Diagram Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 1 Pin Configuration Note: The package exposed pad is electrically connected inside the package to AGND. Functional Pin Description Pin Number Name Function 1 EN Chip Enable (Active High). Note that this pin is high impedance. There should be a pull low 100kΩ resistor connected to GND when the control signal is floating. 2 CTR0 Output Control Bit 0. (See Table 1) 3 CTR1 Output Control Bit 1. (See Table 1) 4 AGND Analog Ground 5 RSET LED current is set by the value of the resistor RSET connected from the RSET pin to ground. Do not short the RSET pin. VISET is typically 1.1V. All external capacitance at this pin, including board parasitic capacitance, must be less than or equal to 30pF. 6 VOUT Output Voltage Source for connection to the LED anodes. 7 VIN Input Voltage 8 C1+ Positive Terminal of Bucket Capacitor 1 9 C1- Negative Terminal of Bucket Capacitor 1 10 NC No Connection 11 NC No Connection 12 PGND Power Ground. This ground should be connected to Power GND on PCB. 13 to16 LED 4 to 1 Current Sink for LED. (If not in use, pin should be connected to VOUT) Exposed Pad GND Exposed pad should be soldered to PCB board and connected to GND. Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 2 Absolute Maximum Rating (1) Parameter Value Units VIN, VOUT, LEDx voltage -0.3～7V V EN, CTRx,RSET voltage -0.3 to VIN V RSET current ±1 mA Lead Temperature (Soldering, 5 sec.) 260 °C Junction Temperature 0 to +150 °C Storage Temperature -40 to +150 °C Operating Rating (2) Parameter Symbol Value Units Supply Input Voltage Range VIN 5.5 V Junction Temperature Range TJ 0 to +125 °C 0to 30 mA I LED per LED pin Electrical Characteristics VIN = 3.5V; C1＝1.0μF; TJ = 25°C; unless otherwise noted Parameter Symbol Input Supply Voltage Min Typ Max Unit VIN 2.85 -- 5.5 V RSET Regulated Voltage VRSET 1.22 1.25 1.28 V Current into LEDs ILED RSET=100K -- 5 -- mA RSET=25.0 K -- 20 -- mA RSET=16.7 K -- 30 -- mA EN=Low, Shutdown Mode -- 1 -- uA 1x Mode , No Load -- 170 -- uA 2x Mode, No Load -- 2.5 -- mA Quiescent Current IQ Conditions ILED Accuracy ILED-ERR 2mA<ILED<30mA -- 2 7.5 % Current Matching(3) ILED-LED-ERR 2mA<ILED<30mA -- 1 5 % VTRANS VLED=3.5V,IOUT=80mA,ILED=20mA -- 3.8 -- V Oscillator Frenquency FOSC VLED=3.5V,IOUT=80mA,ILED=20mA -- 1.0 -- MHz Input High Threshold VIH Input high logic threshold 1.5 -- -- V Input Low Threshold VIL Input low logic threshold -- -- 0.4 V Input Leakage Current IIN -- -- 1 μA x1 mode to x2 mode Transition Voltage(VIN falling) TPROTECTION Thermal Thermal Protection Temperature -- 150 -- Protection Protection Hysterisys -- 20 -- Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 3 °C Control Inputs Output Status CTRL1 CTRL0 LED4 LED3 LED2 LED1 0 0 OFF OFF ON ON 0 1 OFF ON ON ON 1 0 ON ON ON ON 1 1 OFF OFF OFF OFF Table1 Note 1: Exceeding the absolute maximum rating may damage the device. Note 2: The device is not guaranteed to function outside its operating rating. Note 3: Current Matching refers to the difference in current from on LED to the next. ILED Current Matching = ± I LED ( MAX ) − I LED ( MIN ) I LED ( MAX ) + I LED ( MIN ) × 100% Operations Thermal Shutdown The SE3362 is a high efficiency charge pump white The SE3362 provides a high current capability to drive 4 LED driver. It provides 4 channels low drop-out voltage white LEDs. A thermal shutdown circuit is needed to current source to regulated 4 white LED’s current. For protect the chip from thermal damage. When the chip high efficiency, the SE3362 implements x1/x2 mode reaches the shutdown temperature 150°C, the thermal charge pump. An external RSET is used to set the shutdown circuit turns off the chip to prevent the thermal current of white LED. accumulation in the chip. Dimming Control Short Circuit Protection CTRL0 and CTRL1 are used to control the on/off of The SE3362 provides short circuit protection function. White LED. When an external PWM signal is connected When output Voltage is shorted to GND, short circuit to the control pin, brightness of white LED is adjusted by protection cell shutdown ChargePump and current the duty cycle. The SE3362 supports the dimming source, and consequently the IC and the related LED’s control frequency up to 1KHz. are protected. LED Current Setting The current of white LED connected to SE3362 can be set by RSET. The channel current that flows through the white LED is 400 times greater than the current of RSET. The white LED can be estimated by following equation: ⎛ V RSET ⎝ RSET ILED = 400× ⎜⎜ ⎞ ⎟⎟ ⎠ where VRSET = 1.25V, and RSET is the resistance connected from RSET to GND. Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 4 Applications Information Selecting Capacitors ILED(A) = To get the better performance of SE3362, the selecting of 500(V ) RSET (Ω) peripherally appropriate capacitor and value is very LED current and Table 2 shows the values of RSET for a important. These capacitors determine some parameters fixed LED current. such as input and output ripple, power efficiency, maximum ILED(mA) RSET (KΩ) supply current by charge pump, and start-up time. To 5 100 reduce the input and output ripple effectively, the low ESR 10 50 15 33.3 reduce the output ripple, increasing the output capacitance 20 25.0 COUT is necessary. However, this will increase the start-up 25 20 time of output voltage. 30 16.7 ceramic capacitors are recommended. Generally, to Table 2 For LED driving applications, the input voltage ripple is more important than output ripple. Input ripple is controlled by input capacitor CIN, increasing the value of input LED current setting with NMOS capacitance can further reduce the ripple. Practically, the LED current setting control can also be achieved by using input voltage ripple depends on the power supply’s the external NMOS to change equivalent resister of RSET impedance. If a single input capacitor CIN cannot satisfy the pin. Figure 2 shows this application circuit of method. For requirement of application, it is necessary to add a this example, a 3 bit signals can set 8 kinds of different low-pass filter as shows in Figure 1. equivalent resister of RSET pin, i.e. produce 8 kinds of LED current level. Table 3 shows the relation between equivalent resister of RSET pin and control signal. Figure1. C-R-C filter used to reduce input ripple The flying capacitor C1 determines the supply current capability of the charge pump and to influence the overall efficiency of system. The lower value will improve efficiency, but it will limit the LED’ s current at low input voltage. Setting the LED Current The SE3362 can be set a fixed LED’s current by a resister RSET connected from RSET to GND. RSET establishes the reference current and mirrors the current into LED1, LED2, Figure 2. The application circuit of setting LED current LED3, and LED4. The current into LED is about 400 times which using a NMOS to set RSET. of the current flows through the RSET, the approximate setting formula is given as follows: Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 5 Table 3. The relation between control signal and equivalent resister of RSET pin S1 S2 S3 Equivalent Resister of RSET pin ( RSET ) 0 0 0 RSET = R4 0 0 1 RSET = R3//R4 0 1 0 RSET = R2//R4 0 1 1 RSET = R2//R3//R4 Figure 3. The PWM dimming application circuit 1 0 0 RSET = R1//R4 for 4WLEDs 1 0 1 RSET = R1//R3//R4 1 1 0 RSET = R1//R2//R4 1 1 1 RSET = R1//R2//R3//R4 LED Dimming Control Methods The SE3362 can use two methods to achieve the LED dimming control. These methods are detailed described Figure 4. The PWM dimming application circuit as following: for 3WLEDs (1) Dimming using PWM signal into CTRL0 and CTRL1 LED current can be controlled by applying a PWM signal to CTRL0 or CTRL1. Table 1 shows the relationship between CTRLx and 4 LED's current states. For an example, as the CTRL1 is pulled logical high and CTRL0 receives a PWM signal, then, four LED’s will be dimmed synchronously. Here, the PWM signal setting the LED's current ON/OFF can achieve the average LED's current which in design. The application circuit is shown in Figure Figure 5. The PWM dimming application circuit for 2WLEDs 3. Figure 4, and Figure 5 show 3WLEDs and 2WLEDs PWM dimming application circuit, respectively. During the time of PWM signal logical low, the current is a fixed value and setting by RSET resistor. So the average LEDs current can be approximated as Equation. ILED(AVG) = Additionally, SE3362 has 100us delay time between mode transfer. This delay time makes different dimming frequency corresponds to TOFF × I LED ( ON ) different maximum duty of CTRLX pin. Please note TPWM that the maximum dimming frequency can not exceed the maximum dimming frequency which is Where: TPWM is the period of PWM dimming signal TOFF is the internally set at 1KHz. time of PWM signal at low. ILED(ON) is LED on state current. Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 6 The following equation shows the relation between 4. The PWM frequency should be in the range of maximum duty of CTRLX pin and PWM dimming 500Hz~1.5kHz or 20kHz~30kHz for audio noise frequency. Table 4 is shown the common dimming consideration. frequency and its corresponding maximum duty. For 5. The PWM duty cycle shall be in the range of 30% to better performance consideration, the maximum PWM 95%. dimming frequency is recommended below 1kHz. 6. The driving capability of the GPIO should be greater D(MAX) = (1-100×10-6×FD) than 2mA @ 2.8V. Table 4. The common dimming frequency and its corresponding maximum duty. Dimming CTRLX RLED Frequency (Hz) Maximum Duty Minimum Duty 1000 0.90 0.10 900 0.91 0.09 800 0.92 0.08 700 0.93 0.07 600 0.94 0.06 500 0.95 0.05 400 0.96 0.04 300 0.97 0.03 200 0.98 0.02 7. The LED current can be obtained by the equation, ILED = 400× V RSET × (1 − DPWM ) RSET (The typical value of VRSET is 1.25V) (2). The PWM dimming by GPIO The PWM dimming by GPIO is shown as Figure 6. DZ shall be a Schottky diode with forward voltage less Figure 6. The GPIO PWM dimming application circuit than 0.3V at IF = 1mA. C3 is a capacitor to keep the enable pin voltage is higher than the threshold voltage. R1 is discharge resister and it should be not too high to prevent the off time too long while turned-off. The recommended conditions are shown as following. 1. The recommended value for R1 and C3 are 200kΩ (±5%) and 0.22μF (X7R, ±10%). 2. The forward voltage of the Schottky diode shall be less than 0.3V at 1mA. 3. The output voltage of GPIO should be greater than 2.8V and keep the voltage on EN pin is higher than 1.5V. Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 7 Outline Drawing for QFN16 3X3 Customer Support Seaward Electronics Incorporated – China Section B, 2nd Floor, ShangDi Scientific Office Complex, #22 XinXi Road Haidian District, Beijing 100085, China Tel: 86-10-8289-5700/01/05 Fax: 86-10-8289-5706 Seaward Electronics Corporation – Taiwan 2F, #181, Sec. 3, Minquan East Rd, Taipei, Taiwan R.O.C Tel: 886-2-2712-0307 Fax: 886-2-2712-0191 Seaward Electronics Incorporated – North America 1512 Centre Pointe Dr. Milpitas, CA95035, USA Tel: 1-408-821-6600 Last Updated - 12/4/2008 Revision 12/4/2008 Preliminary and all contents are subject to change without prior notice © Seaward Electronics, Inc., 2007. • www.seawardinc.com.cn • Page 8