Part No. Package Marking Material Packing SD42530 HSOP SD42530 Pb free Tube SD42530TR HSOP SD42530 Pb free Tape&Reel

Transcription

1 4-CHANNEL 1A HIGH POWER LED DRIVER WITH 6~48V INPUT DESCRIPTION The SD4253 is a step-down PWM control LED driver with a builtin power MOSFET. It achieves 1A continuous output current in 6~48V input voltage range. It provides thermal shutdown circuit, current limit circuit and PWM dimming circuit. The SD4253 adopts current mode control which provides fast transient response, excellent constant current characteristic and simple loop stabilization design. It has high efficiency up to more than 96%, and has excellent constant current characteristic when the input/output voltage changed, with the excellent current accuracy within ±1.5%. HSOP FEATURES * 6-48V input voltage range * Four synchronous PWM dimming function * Synchronous switching for four power MOSFETs * Shutdown mode with Iq=2μA * Voltage on SENSE is set by pin ADJ * Maximum 1A output current *.6Ω built-in power NMOSFET * Frequency jitter * 3kHz fixed frequency * Excellent constant current accuracy ±1.5% * Current accuracy ±3% * High efficiency up to 96% when multiple LEDs connected in series * Thermal shutdown * Over current protection * ADJ low voltage detection * Open circuit detecting protection * 9% maximum duty cycle operation APPLICATIONS * LED building illumination * LED street lamp ORDERING INFORMATION Part No. Package Marking Material Packing SD4253 HSOP SD4253 Pb free Tube SD4253TR HSOP SD4253 Pb free Tape&Reel Page 1 of 11

2 BLOCK DIAGRAM X=1,2,3,4 7 EN VREF 14 VIN LDO 9 VDD SENSE_X SW_X 1.2V ADJ 21 PWM 1 COMP_X OSC IREF OSC ISLOPEX PWM CTRL + - EA PWM Comparator + - SLOPE Compensation S R R Q PGND_X + - ILIMIT VDD DRIVER ILIMIT Comparator ISENSE + - AGND ABSOLUTE MAXIMUM RATING Characteristics Symbol Ratings Unit Supply Voltage V IN 48 V Switch Voltage (1,2,3,4) V SW 6 V PWM Voltage V PWM -.3~6 V Comp Voltage (1,2,3,4) V COMP -.3~6 V VDD Voltage V DD -.3~6 V EN Voltage V EN -.3~6 V ADJ Voltage V ADJ -.3~6 V SENSE Voltage (1,2,3,4) V SENSE -.3~V IN V Junction Temperature Tj 15 C Lead Temperature (1 sec) T L1 26 C Infrared/Convection Reflow (15 sec) T L2 235 C Operating Temperature Range T OPR -4~85 C Storage Temperature Range T STG -65~125 C Page 2 of 11

3 ELECTRICAL CHARACTERISTICS (Unless otherwise specified, V IN =12V, V EN =5V, I OUT =7mA, T amb =25 C) Characteristics Symbol Test Condition Min. Typ. Max. Unit Supply voltage V IN V Quiescent operating current 1 I IN_PWMON V CC =6/48V,V PWM =5V ma Quiescent operating current 2 I IN_PWMOFF V CC =6/48V,V PWM =V ma Off operating current I IN_ENOFF V CC =6/48V,V EN =V μa Upper switch leakage μa I Leakage V SW =6V -- 5 current (1,2,3,4) Peak current limit I LIM Short Rsense A Maximum duty cycle D max V IN drops with Vo fixed % Oscillator frequency F osc khz PWM on voltage V PWMON V PWM is from V to 5V, On voltage V PWM off voltage V PWMOFF V PWM is from 5V to V, Off voltage V PWM pull-up current I PWM1 V PWM =V μa PWM pull-down current I PWM2 V PWM =5V μa EN pull-up current I EN V EN =V μa EN on voltage V ENON V EN is from V to 5V, On voltage V EN off voltage V ENOFF V EN is from 5V to V, Off voltage V COMP clamp voltage V COMP Open without load V Switch transistor on resistance (1,2,3,4) R ON 1LED,I OUT =.5A Ω VDD voltage V DD No load V ADJ threshold voltage ADJ off threshold voltage ADJ on threshold voltage Sense voltage threshold Over temperature protection threshold Over temperature recovery threshold V ADJ V ADJ is from 5V to V and the V output current decreased. V ADJOFF V ADJ is from 1V to V, off voltage mv V ADJON V ADJ is from V to 1V, on voltage mv V IN -V SENSE Voltage drop between V IN and SENSE mv T OVP Rising temperature C T RECOVERY Falling temperature C Page 3 of 11

4 PIN CONFIGURATION PIN DESCRIPTION Pin No. Pin Name I/O Description 1 PWM I PWM dimming input 2,13,16,27 COMP1,2,3,4 I/O Compensation pins, each is connected with an external 3,12,17,26 SW1,2,3,4 I/O Switch nodes 4,11,18,25 PGND1,2,3,4 I Power ground 6,8,15,2,23,28 NC No connection 5,1,19,24 SENSE1,2,3,4 I Current sense input 7 EN I Enable input 9 VDD I/O 5V linear power supply output 14 VIN I Input power 21 ADJ I Analog dimming input 22 AGND I Analog ground Page 4 of 11

5 FUNCTION DESCRIPTION The SD4253 is a current mode LED driver. The voltage on compensation pin COMP is proportional to the current delivered to the load. Four channels are in synchronous mode, which means the power switches are on or off at the same time. When the external working conditions are exactly the same, the operating principle of each channel is the same with that of SD At the beginning of a cycle: the power MOSFET MX is off; the voltage on pin COMP is higher than the current sense amplifier output, and the current comparator s output is low. The falling edge of the CLK signal sets RS Flip-Flop whose output turns on the MX of four-channel thus V IN, R S, LED, inductor and MX comprises a circuit loop and the inductor current increases. The inductor current is sensed and amplified by the current sense amplifier. Ramp compensation is superimposed on the current sense amplifier output and compared to the Gm amplifier output by the current comparator, and when the former exceeds the latter, the RS Flip-Flop is reset and MX is off. Due to the inductor current can not be changed abruptly, the inductor energy storage released via the circuit loop composed by R S, LED, inductor and MX and the current decreases. When next clock cycle arrives, the power MOSFET MX is on to enter next switch cycle. If the current sense amplifier plus slope compensation signal does not exceed the output voltage of Gm amplifier in one cycle, then the Flip-Flop keeps set and MX remains on state. The Gm amplifier compares the output current with the threshold current (threshold current is set by internal). When the output current is higher than threshold current, the voltage on pin COMP reduced. Since the voltage on pin COMP is proportional to the inductor peak current, a decrease in its voltage decreases current delivered to the output. When the output current is lower than threshold current, the voltage on pin COMP rises while the output current increases. The output current is stable at the set value by adjusting the circuit loop. If special situations happen, for example, one channel is short or the quantity of connected LEDs of one channel is less than that of other channels, then the current comparator of this channel will output high in advance which will be selected to set the four RS Flip-Flops. 1. PWM dimming SD4253 has internal PWM dimming function to process the dimming of the four-channel at the same time. When the pin PWM is connected to high level, the chip is working normally; when the pin PWM is open or connected to low level, and pin COMP is disconnected with the chip, the charge of the capacitor is in hold state, the voltage level holds, the output of current comparator is high, and the power MOSFET is off without output current. When PWM signal is high, the pin COMP is connected with the chip to improve the startup speed of the chip. Adjust the output current by control the duty cycle of external PWM signal. The minimum setup time of SD4253 PWM dimming is less than 2μS, and the maximum PWM dimming ratio is up to 5:1. When high dimming ratio is needed, the dimming frequency is recommended 5Hz below; or else the dimming frequency can be up to 2 KHz. 2. Output current setting The output current is determined by the sense resistor and setting voltage. The sense voltage of V IN -V SENSE (Drop voltage on R S ) is 1mV, and the output current can be changed by adjusting the sense resistor R S (refer to Typical Application Circuit). Page 5 of 11

6 I OUT V = IN V R SENSE S 3. Current limiting SD4253 has internal current limiting function, and the voltage on COMP is clamped at about 2.2V, the output current of the power MOSFET is limited at about 2A by the current comparator. 4. Frequency jitter SD4253 has internal frequency jitter function to improve the EMI performance of the system. The internal frequency is hopping in a very small range to reduce the single frequency radiation which simplifies the EMI design. 5. Thermal compensation and linear dimming function SD4253 integrated linear dimming and thermal compensation function. Linear dimming: Set the output current by setting the ratio of R1 and R2. The relation between voltage on pin ADJ and output current I OUT : VA DJ 1.22V,.1 I OUT = R.8V V DJ < A < 1.22V, IOUT = RS S.1 V ADJ <.8V, I = The ADJ voltage is detected automatically and if it is less than.8v, then I OUT =, so the general problem that the LED can not be completely off can be solved. Thermal compensation: See the typical application circuit, R2 can be replaced by NTC resistor for thermal compensation function. The voltage on R2 is more than 1.22V under normal temperature with 1% output current, while the LED temperature detected by R2 is more than the setting value Tth, the voltage on R2 is less than 1.22V with the decreasing current output following the rising temperature. Therefore, different falling curve of LED current can be achieved by connecting NTC resistor R2 with other resistors in series. If ADJ is connected to VDD, thermal compensation and linear dimming functions will not be available. OUT V ADJ 1.22 The relation between LED output current and temperature 6. Thermal shutdown The thermal shutdown function of SD4253 protects the IC when the IC temperature is more than 15 C, and the pin COMP is pulled low while the power MOSFET is off. The thermal shutdown function is working until the IC Page 6 of 11

7 temperature decreased to less than 13 C. 7. Open-circuit detection & protection SD4253 adopts open-circuit detection, and voltage at pin COMP is pulled to V. So the COMP voltage and inductor current increase from zero in operation to decrease overshoot current for the safety. 8. Short-circuit protection SD4253 can protect IC when output is shorted in operation. It adjusts COMP voltage and reduce the switching frequency, also the peak current is limited by the current limiting comparator. 9. Maximum duty cycle operation When SD4253 operates at maximum duty cycle or larger, the switching frequency will fall following that Vin drops, but output current will keep unchanged and decreases until Vin approaches to Vout. The internal switch is on all the time. COMPONENTS SELECTION 1. Input Capacitor Selection The input capacitor provides the pulse current when the power MOSFET is on, and charge the capacitor when the power MOSFET is off, thus to keep the stability of the input voltage. The input capacitor is recommended to be more than 1μF, which can reduce the peak current drawn from input source and the switch noise. The input capacitor should be near to the input pin in real routing. 2. Output Capacitor Selection Parallel connecting a capacitor between the two ends of LED can reduce the output voltage ripple accordingly reduce the ripple current of LED, while this capacitor will not effect the operating frequency and efficiency, but the start time will be longer by reducing the rising speed of the voltage on LED. The larger the output capacitor is, the smaller the current ripple on LED is. It is recommend use the capacitor of 2.2μF or larger. 3. Inductor Selection The inductor is used to keep the output current constant, the bigger the inductance is, the smaller the output current ripple is; while the bigger the physical size is, the bigger the series-wound resistor is. The selected effective current (RMS current rating)of inductor current should be bigger than the maximum output current, and the saturation current should be 3% bigger than maximum output current. In order to improve the efficiency, the series-wound resistor (DCR) of inductor should be smaller than.2ω. The relation between inductance and ripple: VIN VOUT L = VOUT * VIN * f * ΔI Where: L: Inductance value f: Oscillator frequency Page 7 of 11

8 ΔI is ripple current When select inductor, you should consider the combination of various factors to select suitable inductor. 4. Diode Selection SD4253 is a non-synchronous step-down adjuster, so a diode is needed to provide continuous current when the power MOSFET is off. Because the forward voltage of Schottky diode is small, and the reverse continuous current time is short, so it is usually used for continuous current. During the power MOSFET is conducting, the diode will withstand high voltage, so the reverse voltage of selected diode should be bigger than the input voltage. The average current delivered to the diode is I D: I = (1 D) * D I LED I LED is the current of LED. When the input voltage is high with a small duty, I D increases, so the maximum continuous current of the selected diode should be bigger than the output current. TYPICAL APPLICATION CIRCUIT 35mA output current Note: The circuit and parameters are reference only, please set the parameters of the real application circuit based on the real test. Page 8 of 11

9 ELECTRICAL CHARACTERISTICS CURVE (FOR ANY CHANNEL) SD4253 Output 35mA 1 LEDs 12 LEDs 6 LEDs 3 LEDs SD4253 Output 35mA 12 LEDs 1 LEDs 8 LEDs 6 LEDs 3 LEDs 75 1LED LEDs Input voltage(v) Input voltage (V) 1LED Output 35mA efficiency changed following the input voltage Output 35mA current change rate following the input voltage change SD4253 Output 7mA 1 LEDs 12 LEDs 6 LEDs SD4253 Output 7mA 12 LEDs 85 3 LEDs.5 1 LEDs LED LEDs 6 LEDs 3 LEDs 2 LEDs 1LED Input voltage(v) Input voltage (V) Output 7mA efficiency changed following the input voltage Output 7mA current change rate following the input voltage 35mA 3 LED Output current (ma) 35 SD4253 Output current (ma) Input voltage (V) Output current change curve when input voltage is close to output voltage(35ma) Output current change curve when input voltage is close to output voltage(7ma) Page 9 of 11

10 ELECTRICAL CHARACTERISTICS CURVE (continued) LED VIN=36V 5Hz 1Hz 1kHz 2kHz Duty cycle % LEDs VIN=36V 5Hz 1Hz 1kHz 2kHz Duty cycle % PWM dimming behavior of 1 LED(7mA) PWM dimming behavior of 3 LEDs(7mA) LEDs VIN=36V 6 12 LEDs VIN=48V Hz 1Hz 1kHz 2kHz Hz 1Hz 1kHz 2kHz Duty cycle % Duty cycle % PWM dimming behavior of 6 LEDs(7mA) PWM dimming behavior of 12 LEDs(7mA) Page 1 of 11

11 PACKAGE OUTLINE HSOP UNIT: mm MOS DEVICES OPERATE NOTES: Electrostatic charges may exist in many things. Please take following preventive measures to prevent effectively the MOS electric circuit as a result of the damage which is caused by discharge: The operator must put on wrist strap which should be earthed to against electrostatic. Equipment cases should be earthed. All tools used during assembly, including soldering tools and solder baths, must be earthed. MOS devices should be packed in antistatic/conductive containers for transportation. Disclaimer : Silan reserves the right to make changes to the information herein for the improvement of the design and performance without further notice! Customers should obtain the latest relevant information before placing orders and should verify that such information is complete and current. All semiconductor products malfunction or fail with some probability under special conditions. When using Silan products in system design or complete machine manufacturing, it is the responsibility of the buyer to comply with the safety standards strictly and take essential measures to avoid situations in which a malfunction or failure of such Silan products could cause loss of body injury or damage to property. Silan will supply the best possible product for customers! Page 11 of 11