FR9708S6

FR9708 24V, 1.5A, 1.2MHz LED Driver with Dimming Control Description Features The FR9708 is a current mode, control LED driver IC. It provides wide 2.8V to 24V input voltage range and 1.5A output current capability.            The FR9708 includes a PWM dimming input that can accept an external control signal with a duty ratio of 5% to 100% and PWM dimming is from 100Hz to 50kHz(Follow EN turn-on delay time). It also supports 0.65V to 1.2V analog dimming input which can be used for linear dimming of the LED current. The FR9708 fault protection includes current limit, input OVP, UVLO and thermal shutdown. The soft-start function prevents inrush current at turn-on. Internal compensation function reduces external compensatory components and simplifies the design process. Input Voltage Range: 2.8V to 24V 1.5A Output Current 1.2MHz Switching Frequency 200mΩ Integrated Power MOSFET 100mV Reference Voltage Analog and PWM Dimming Techniques Cycle-by-Cycle Current Limit Over-Temperature Protection with Auto Recovery Input Under Voltage Lockout Input Over Voltage Protection SOT-23-6 Package Applications    LED Driver IP Camera LED Flashlights Pin Assignments Ordering Information S6 Package: SOT-23-6 FR9708□ Package Type S6: SOT-23-6 Package ISEN VIN EN/D 6 1 5 4 (Marking) 2 3 LX GND NC Figure 1. Pin Assignments of FR9708 FR9708-1.0-NOV-2021 SOT-23-6 Marking Part Number Product Code FR9708S6 FU2 1 FR9708 Typical Application Circuit RSEN VIN C1 10μF PWM or Analog Signal LED 6 ISEN 5 VIN 4 EN/D C2 1μF D1 FR9708 L1 6.8μH LX 1 3 NC LED GND 2 Figure 2. Buck Application Circuit L1 6.8μH D1 VIN 1 LX C1 10μF PWM or Analog Signal VIN 4 EN/D 5 C3 1μF FR9708 ISEN RSEN C2 1μF RSEN C2 1μF 6 LED 3 NC GND 2 LED Figure 3. Boost Application Circuit L1 6.8μH D1 VIN 1 LX C1 10μF PWM or Analog Signal VIN 4 EN/D 5 C3 1μF FR9708 ISEN 6 LED 3 NC GND 2 LED Figure 4. Buck-Boost Application Circuit Note 1: LED dimming control can be done from either analog or PWM signal at the EN/D pin. FR9708-1.0-NOV-2021 2 FR9708 Functional Pin Description Pin Name Pin No. Pin Function LX 1 Power switching node. Connect an external inductor to this switching node. GND 2 Ground pin. NC 3 No connection. Keeps this pin floating. EN/D 4 Enable control input and dimming control input. Logic high enables operation. This pin can select analog or PWM dimming controls the brightness of LEDs. VIN 5 Power supply input pin. Placed input capacitors as close as possible from VIN to GND to avoid noise influence. ISEN 6 Current sense input pin. Connect an external resistor from VIN to ISEN to set the LED current. Block Diagram VIN UVLO & POR EN/D 1M Internal Regulator VCC Input OVP OTP Oscillator Analog & PWM Dimming Control LX S ISEN ISEN VIN Current Comp R Control Logic Driver Logic Internal MOSFET OTP UVLO Current Limit GND Figure 5. Block Diagram of FR9708 FR9708-1.0-NOV-2021 3 FR9708 Absolute Maximum Ratings (Note 2) ● Supply Voltage VIN ------------------------------------------------------------------------------------------- -0.3V to +28V ● Enable Voltage VEN/D ---------------------------------------------------------------------------------------- -0.3V to +28V ● ISEN VISEN ----------------------------------------------------------------------------------------------------- -0.3V to +28V ● LX Voltage VLX ------------------------------------------------------------------------------------------------ -0.3V to VIN +0.3V ● All Other Pins Voltage -------------------------------------------------------------------------------------- -0.3V to +6V ● Maximum Junction Temperature (TJ) ------------------------------------------------------------------- +150°C ● Storage Temperature (TS) --------------------------------------------------------------------------------- -65°C to +150°C ● Lead Temperature (Soldering, 10sec.) ----------------------------------------------------------------- +260°C ● Package Thermal Resistance, (θJA) (Note 3) SOT-23-6 ------------------------------------------------------------------------------------------ 250°C/W ● Package Thermal Resistance, (θJC) SOT-23-6 ------------------------------------------------------------------------------------------ 110°C/W Note 2: Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device. Note 3: θJA is measured at 25°C ambient with the component mounted on a high effective thermal conductivity 4-layer board of JEDEC-51-7. The thermal resistance greatly varies with layout, copper thickness, number of layers and PCB size. Recommended Operating Conditions ● Supply Voltage VIN ------------------------------------------------------------------------------------------ +2.8V to +24V ● Operation Temperature Range --------------------------------------------------------------------------- -40°C to +85°C FR9708-1.0-NOV-2021 4 FR9708 Electrical Characteristics (VIN=12V, TA=25°C, unless otherwise specified.) Parameter Symbol Conditions VIN Quiescent Current IDDQ VEN/D=1.2V, VISEN=0.3V VIN Shutdown Supply Current ISD VEN/D=0V Reference Voltage VREF MOSFET RDS(ON) RDS(ON) MOSFET Leakage Current ILX(leak) Min 96 Typ Max Unit 100 200 μA 10 μA 104 mV 100 mΩ 200 VEN/D=1.2V, VLX=24V 10 LX Current Limit ILIMIT Oscillation Frequency FOSC 1.2 MHz Maximum Duty Cycle DMAX 100 % TMIN 100 ns 2.5 V 200 mV Minimum On Time (Note 4) Input Supply Voltage UVLO Threshold VUVLO(Vth) Input Supply Voltage UVLO Threshold Hysteresis VUVLO(HYS) 1.7 μA VIN Rising EN/D High-Level Input Voltage VEN/D VEN/D Rising EN/D Low-Level Input Voltage VEN/D VEN/D Falling EN Turn On Delay 0.65 VEN_DELAY Analog Dimming Range A V 12 VEN/D 0.65 0.3 V 35 us 1.2 V Analog Dimming Scale VEN/D = 0.65V 5 % Analog Dimming Scale VEN/D = 1.2V 100 % VIN_OVP 26.7 V TSD 150 °C THYS 20 °C Input Over Voltage Protection Thermal Shutdown Temperature Thermal Shutdown Hysteresis (Note 4) (Note 4) Note 4: Not production tested. FR9708-1.0-NOV-2021 5 FR9708 Typical Performance Curves VIN=12V, IOUT=1.0A, 1S2P LED VIN=15V, IOUT=1.0A, 2S2P LED SW SW 5V/div. 5V/div. VLED 1V/div. IL 500mA/div. VLED IL 2V/div. 500mA/div. 1μs/div. 1μs/div. Figure 6. Switching Waveform Figure 7. Switching Waveform VIN=24V, IOUT=1.0A, 5S2P LED SW VLED IL VIN=12V, IOUT=1.0A, 1S2P LED 10V/div. VIN 5V/div. SW 5V/div. VLED 2V/div. ILED 500mA/div. 5V/div. 1A/div. 1μs/div. 10ms/div. Figure 8. Switching Waveform Figure 9. Power On Through VIN Waveform VIN=12V, IOUT=1.0A, 1S2P LED VIN=12V, IOUT=1.0A, 1S2P LED VIN 5V/div. SW 5V/div. VLED 2V/div. ILED 500mA/div. 20ms/div. Figure 10. Power Off Through VIN Waveform FR9708-1.0-NOV-2021 VEN 1V/div. SW 5V/div. VLED 2V/div. ILED 500mA/div. 2ms/div. Figure 11. Power On Through EN Waveform 6 FR9708 Typical Performance Curves (Continued) VIN=12V, IOUT=1.0A, 1S2P LED VEN 1V/div. SW 5V/div. VLED ILED 2V/div. 500mA/div. 100ms/div. Figure 12. Power Off Through VEN Waveform Figure 13. Efficiency vs. Input Voltage (IOUT=1.0A) Figure 14. Switching Frequency vs. Input Voltage (IOUT=0.5A) Figure 15. Switching Frequency vs. Ambient Temperature (IOUT=0.5A, 2S2P LED) Figure 16. Quiescent Current vs. Ambient Temperature Figure 17. Reference Voltage vs. Ambient Temperature (IOUT=0.5A, 2S2P LED) FR9708-1.0-NOV-2021 7 FR9708 Typical Performance Curves (Continued) Figure 18. EN/D Voltage vs. Ambient Temperature (IOUT=0.5A, 2S2P LED) Figure 19. LED Current vs. EN Voltage (VIN=12V) Figure 20. LED Current vs. PWM Duty (VIN=12V, 3S2P LED) Figure 21. LED Current vs. PWM Duty (VIN=12V, 3S2P LED) FR9708-1.0-NOV-2021 8 FR9708 Function Description The FR9708 is constant frequency and current mode control LED driver IC. It has integrated 200mΩ power MOSFET, and provides 1.5A output current. It regulates input voltage from 2.8V to 24V. Over Current Protection The stability of the ISEN circuit is controlled through internal compensation circuits. This internal compensation function is optimized for most applications and this function can reduce external R, C components. The FR9708 over current protection function is implemented using cycle-by-cycle current limit architecture. The inductor current is monitored by measuring the MOSFET series sense resistor voltage. When the load current increases, the inductor current also increases. When the inductor current reaches the current limit threshold, the output voltage starts to drop. When the over current condition is removed, the output voltage returns to the regulated value. Enable and Dimming Control Over Temperature Protection The FR9708 EN/D pin provides digital control to enable and disenable the converter. When the voltage of EN/D exceeds the threshold voltage, the FR9708 will operate enables. If the EN/D pin voltage is below than the shutdown threshold voltage, the FR9708 will turn into the shutdown mode and the shutdown current is around 10μA (typ). This pin includes a 0.65V to 1.2V analog dimming input which can be used for linear dimming of the LED current. It includes a PWM dimming input that can accept an external control signal with a duty ratio of 5% to 100% and PWM dimming is from 100Hz to 50kHz (Follow EN turn-on delay time). The FR9708 incorporates an over temperature protection circuit to protect itself from overheating. When the junction temperature exceeds the thermal shutdown threshold temperature, the regulator will be shutdown. And the hysteretic of the over temperature protection is 20°C (typ). Internal Compensation Function Input Under Voltage Lockout When the FR9708 is power on, the internal circuits are held inactive until VIN voltage exceeds the input UVLO threshold voltage. And the regulator will be disabled when VIN is below the input UVLO threshold voltage. The hysteretic of the UVLO comparator is 200mV (typ). Input Over Voltage Protection When the VIN pin voltage exceeds 26.7V, the output over voltage protection function will be triggered and turn off the MOSFET. FR9708-1.0-NOV-2021 9 FR9708 Application Information Setting LED Current The LED current ILED is set using a resistor from the VIN to ISEN. The ISEN pin regulated voltage is 100mV. Thus the LED current is: The following figures show the form of the ripple contributions. VRIPPLE(ESR)(t) m R Input Capacitor Selection The use of the input capacitor is filtering the input voltage ripple and the MOSFETS switching spike voltage. Because the input current to the step-down converter is discontinuous, the input capacitor is required to supply the current to the converter to keep the DC input voltage. The capacitor voltage rating should be 1.25 to 1.5 times greater than the maximum input voltage. The input capacitor ripple current RMS value is calculated as: (RM (t) + VRIPPLE(ESL) (t) + VRIPPLE(C) (t) (t) + VNOISE (t) (t) T T Where D is the duty cycle of the power MOSFET. A low ESR capacitor is required to keep the noise minimum. To select the X7R (-55°C to 125°C) or X5R (-55°C to 85°C) ceramic capacitors are better, but tantalum or low ESR electrolytic capacitors may also suffice. When using tantalum or electrolytic capacitors, a 0.1μF ceramic capacitor should be placed as close to the IC as possible. = VRIPPLE(t) (t) Output Capacitor Selection The output capacitor is used to keep the DC output voltage and supply the load transient current. When operating in constant current mode, the output ripple is determined by four components: R PP t t R PP R PP ( FR9708-1.0-NOV-2021 t R PP R t R PP ( R PP ( R PP ( R T T F R t T F T T 10 FR9708 Application Information (Continued) Where FOSC is the switching frequency, L is the inductance value, VIN is the input voltage, ESR is the equivalent series resistance value of the output capacitor, ESL is the equivalent series inductance value of the output capacitor and the COUT is the output capacitor. Low ESR capacitors are preferred to use. Ceramic, tantalum or low ESR electrolytic capacitors can be used depending on the output ripple requirement. When using the ceramic capacitors, the ESL component is usually negligible. It is important to use the proper method to eliminate high frequency noise when measuring the output ripple. The figure shows how to locate the probe across the capacitor when measuring output ripple. Removing the scope probe plastic jacket in order to expose the ground at the tip of the probe. It gives a very short connection from the probe ground to the capacitor and eliminating noise. Probe Ground That will lower ripple current and result in lower output ripple voltage. The Δ L is inductor peak-to-peak ripple current: T T F A good compromise value between size and efficiency is to set the peak-to-peak inductor ripple current Δ L equal to 30% of the maximum load current. But setting the peak-to-peak inductor ripple current Δ L between 20%~50% of the maximum load current is also acceptable. Then the inductance can be calculated with the following equation: . T(MA T To guarantee sufficient output current, peak inductor current must be lower than the FR9708 high-side MOSFET current limit. The peak inductor current is as below: GND Load Current P A VOUT T F T(MA IPEAK IOUT(MAX) ∆IL Time Ceramic Capacitor Inductor Selection The output inductor is used for storing energy and filtering output ripple current. But the trade-off condition often happens between maximum energy storage and the physical size of the inductor. The first consideration for selecting the output inductor is to make sure that the inductance is large enough to keep the converter in the continuous current mode. FR9708-1.0-NOV-2021 11 FR9708 Outline Information SOT-23-6 Package (Unit: mm) SYMBOLS UNIT DIMENSION IN MILLIMETER MIN MAX A 0.90 1.45 A1 0.00 0.15 A2 0.90 1.30 B 0.30 0.50 D 2.80 3.00 E 2.60 3.00 E1 1.50 1.70 e 0.90 1.00 e1 1.80 2.00 L 0.30 0.60 Note: Followed From JEDEC MO-178-C. Carrier Dimensions Life Support Policy Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems. FR9708-1.0-NOV-2021 12