ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter Description The ACE716E is a high efficiency step-up converter with an internally integrated 40V power MOSEFT. It runs with an optimal 0.8MHz frequency that enables use of small external components while still providing best efficiencies. It has an internal current limit as high as 1A, and it can drive up to 10 LEDs at 50mA output current. The incorporated 25-100KHz true PWM-Dimming feature by EN pin can be used to digitally program the LED current. For maximum protection, the ACE716E has an internal OVP protection at 38V to prevent the chip from damages when the LED string is not connected to the output. ACE716E is available in a space-saving SOT23-6 package. Features • • • • • • • • Up to 90% Efficiency (6 LEDs) Drive up to 10 LEDs with 50mA Drive up to 40 LEDs in total 38V OVP protection True PWM Brightness Control 200mV Feedback Voltage 1A current limit SOT23-6 Package Application • • • • • • Cellphone and Smartphone MID or Tablet PC TFT-bias for LCD screen Power for OLED LED torch Satellite Set Top Box Absolute Maximum Rating Parameter Value SW Voltage -0.3V~38V All Other PIN Voltages -0.3V~6.5V SW to ground current Internally limited Operating Temperature Range -40℃~85℃ Storage Temperature Range -55℃~150℃ Thermal Resistance (Θjc) SOT23-6 ΘJA 100 ΘJC 50 ℃/W Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. VER 1.2 1 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter Packaging Type SOT-23-6 Ordering information ACE716E XX + H Halogen - free Pb - free GM: SOT-23-6 PIN NAME DESCRIPTION 1 SW Inductor Connection. Connect an inductor Between SW and IN. 2 GND Ground Pin 3 FB Feedback Input for Current. Connect an external resistor FB to GND to set IOUT 4 EN Control pin for the IC. It is default low. It is a multi-functional pin for enable control, PWM dimming 5 NC Not connected, leave this PIN floating 6 IN Input Supply pin. Bypass with a 4.7μF or larger ceramic capacitor to GND VER 1.1 2 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter BLOCK DIAGRAM Electrical Characteristics (VIN =3.6V, unless otherwise specified.Typical values are at TA=25℃) Parameter Conditions Input Voltage Range FB Feedback Voltage Min Typ 2.7 VIN=VCTRL=3.6V 194 200 FB Input Current Max Unit 6 V 206 mV 2 uA 1.8 mA 5 mA uA Quiescent Current at IN Switching at lout=0 1.0 Quiescent Current at IN Shutdown Supply Current at IN No Switching 0.2 VEN=GND 0 Switching Frequency VIN<4.3V 0.8 MHz 93 % Maximum Duty Cycle 90 NMOS Switch On Resistance lSW=100mA 0.44 Ω NMOS Switch Current Limit VIN*3.6V, 10LEDS 1.0 A SW Leakage Current VSW=0 or 20V, VEN=GND EN Inupt Current 0.1 EN Input Low Voltage EN Input High Voltage 1.2 PWN dimming frequency 25 Thermal Shutdown Rising, Hysteresis=10℃ 10 uA 1 uA 0.6 V V 100 165 KHz ℃ VER 1.1 3 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter Typical Application USB Power Application Circuit VOUT = 0.2x(1+R1/R2) Note: The Pin6, Vin Pin of ACE716E is connected to 5V, not the battery input. Circuit lefthand is only for output than 5.5V! Please connect Pin6 to input if output is to Be larger than 5.5V. VER 1.1 4 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter TFT Bias Application Circuit Typical Application Circuit (Typical values are at TA=25℃ unless otherwise specified) VER 1.1 5 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter VER 1.1 6 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter FUNCTIONAL DECRIPTIONS The ACE716E is a high efficiency boost LED driver with a small package size. The device is ideal for driving 2-25LEDs for backlight application in smartphone and 7-inch tablet PC. The device integrates a 38V/1A switch FET and operates in pulse width modulation (PWM) with a 0.8MHz fixed switching frequency. For operation details, please check the block diagram in the “Block Diagram” chapter. The duty cycle of the converter is set by the error amplifier output and the current signal applied to the PWM control comparator. The feedback loop regulates the FB pin to a low reference voltage (200mV typical), reducing the power dissipation in the current sense resistor. Output Open Circuit Protection Output open circuit protection circuitry prevents IC damage as the result of output open circuit (e.g. LED string absence). The ACE716E monitors the voltage at the SW pin and FB pin during each switching cycle. The circuitry turns off the switch FET and shuts down the IC when both of the following conditions persist for 8 switching clock cycles: (1) the SW voltage exceeds the VOVP threshold, which is 38V and (2) the FB voltage is less than half of regulation voltage. As a result, the output voltage falls to the level of the input supply. The device remains in shutdown mode until it is enabled by toggling the EN pin logic. The output voltage plus the 200mV reference voltage cannot exceed the minimum OVP threshold or OUTPUT VOLTAGE + 200 mV ≤ VOVP(MIN). Shutdown The ACE716E enters shutdown mode when the EN voltage is logic low for more than 3ms. During shutdown, the input supply current for the device is less than 1μA (max). Although the internal FET does not switch in shutdown, there is still a DC current path between the input and the output through the inductor and Schottky diode. For LED driving application, the minimum forward voltage of the LED array must exceed the maximum input voltage to ensure that the LEDs remain off in shutdown. However, in the typical application with two or more LEDs, the forward voltage is large enough to reverse bias the Schottky and keep leakage current low. LED Driving Current Setting The FB voltage is regulated by a low 0.2V reference voltage. The LED current is set externally using a current-sense resistor in series with the LED string. The value of the RSET is calculated using Equation 1.2: ILED =0.2/RSET (1.2) Where ILED = output current of LEDs, RSET = current sense resistor The output current tolerance depends on the FB accuracy and the current sensor resistor accuracy. PWM Dimming Control or Output Voltage Programming When the CTRL pin is constantly high, the FB voltage is regulated to 200mV typically. However, the EN pin allows a PWM signal to reduce this regulation voltage; therefore, it achieves LED brightness dimming or output voltage programming (only to make output voltage lower). The relationship between the duty cycle and FB voltage is given by Equation 2. VER 1.1 7 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter VFB =Duty*200 mV (2) Where Duty = duty cycle of the PWM signal, 200 mV = internal reference voltage This PWM dimming eliminates the audible noise which often occurs when the output current is pulsed in replica of the frequency and duty cycle of PWM control. Unlike other scheme which filters the PWM signal for analog dimming, ACE716E regulation voltage is independent of the PWM logic voltage level which often has large variations For optimum performance, use the PWM dimming frequency in the range of 25kHz to 100kHz. APPLICATION INFORMATION Inductor Selection Using an inductor with a smaller inductance value forces discontinuous PWM when the inductor current ramps down to zero before the end of each switching cycle. This reduces the boost converter’s maximum output current, causes large input voltage ripple and reduces efficiency. Large inductance value provides much more output current and higher conversion efficiency. For these reasons, a 15μH to 22μH inductor value range is recommended. A 15μH inductor optimized the efficiency for most application while maintaining low inductor peak to peak ripple. Below table lists the recommended inductor for the ACE716E. Recommended Inductors for ACE716E L(uH) Saturation Current (mA) 4.7- 15 >1500 Vendor Sunlord Schottky Diode Selection A high-speed rectifying Schottky with low parasitic capacitance is recommended for ACE716E for maximum efficiency due to its high switching frequency. The diode average and peak current rating must be larger than the average output current and peak inductor current to ensure reliability. In addition, the diode’s reverse breakdown voltage must exceed the open LED protection voltage. Input and Output Capacitor Selection The output capacitor is mainly selected to meet the requirements for the output ripple and loop stability. The output requires a capacitor in the range of 2.2μF to 10μF. VER 1.1 8 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter Packing Information SOT-23-6 VER 1.1 9 ACE716E Max 38V, Variable Frequency Step-up DC/DC Converter Notes ACE does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ACE Electronics Co., LTD. As sued herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.1 10