HT7963 LED Backlight Driver Features General Description • Integrated high power boost DC-DC controller The HT7963 is a high efficiency boost converter with a fixed oscillator frequency for LED backlighting and LED lighting application. The white LED current is setup using an external current setting resistor, which has a low feed-back voltage of only 0.3V. The DIM input allows a wide range of dimming control for LED backlighting or LED lighting. The device offers a full range of protection functions such as power MOSFET over current protection (OCP), IC power supply under voltage lockout (UVLO), over-voltage protection (OVP), output voltage short circuit protection (OSP) and over temperature protection (OTP). • Wide input voltage range from 9V to 30V • High Voltage Gate-Drive provides lower RDS(ON) and higher efficiencies • Dimming frequency from 100Hz to 1kHz • 0.3V LED feedback current sensing voltage with ±3% tolerance • Device protection features include: Soft-start, OCP, UVLO, OVP, OTP and output short protection – OSP • LED protection: LED Open/Short Protection • Package type: 8-pin SOP Applications • LED Backlighting for LCD TV/Monitor • LED lighting Typical Application Circuit D1 L VIN = 12V~24V VOUT 47uH CIN 220uF COUT 51Ω 47uF R1 10kΩ PWM RC 47KΩ 1 VIN 8 DIM 6 COMP 3 GND HT7963 DRV 2 CS 4 OVP 7 FB 5 0.1uF RCS 10pF R2 optional 100Ω ILED= 0.3V RFB optional 100Ω RFB CC 33nF CFB 470pF Note: The VOUT/VIN ratio is suggested to be lower than 5 to gain better dimming linearity. Rev. 1.00 1 August 14, 2015 HT7963 Block Diagram VIN OTP UVLO 6V/8.5V VIN VREF Pre-Driver OSC 1.938V DRV PWM Comparator OVP clamped to 13V Control Logic OVP GND OSP OCP OVP IDIM OSP 0.1V UVLO LED Short Slope Compensation Dimming Control DIM LEB OCP IDIM CS 0.5V FB GND EA COMP 1.2V 0.3V Soft-start GND LED Short Pin Assignment VIN 1 8 DIM DRV GND 2 7 OVP 3 6 CS 4 5 COMP FB HT7963 8 SOP-A Pin Description Pin Order Name Type 1 VIN P Power Supply Pin Discription 2 DRV O Boost Converter Gate Drive Output 3 GND G Ground Terminal 4 CS I Boost Converter Current Sense Input 5 FB I LED Current Feedback Input 6 COMP I/O 7 OVP I Over Voltage Protection Input – setup using resistor divider 8 DIM I External PWM Dimming Control / Enable Control Boost Converter Loop Compensation Absolute Maximum Ratings Parameter VIN, DRV, CS, FB and OVP GND Value Unit -0.3 to 33 V +/-0.3 V DIM and COMP -0.3 to +7.0 V Operating Temperature Range -40 to +85 °C +160 °C Maximum Junction Temperature Rev. 1.00 2 August 14, 2015 HT7963 Recommended Operating Range Parameter Value Unit VIN 9~30 V CS, OVP and FB ≤30 V DRV (Internal Voltage Clamped) 13 V DIM and COMP 0~5.5 V Dimming Frequency DC to 1000 Hz Dimming Duty Cycle 1 to 100 % ≤125 °C Operating Junction Temperature Note that Absolute Maximum Ratings indicate limitations beyond which damage to the device may occur. Recommended Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specified performance limits. Electrical Characteristics Symbol VIN=12V and Ta=25˚C, unless otherwise specified Parameter Test Condition Min. Typ. Max. Unit Supply Voltage VIN Input Voltage VIN 9 — 30 V ICC1 Operating Current DIM=5V — 2.5 3 mA ICC2 Standby Current DIM=0V — 500 650 μA ISHD Shutdown Current DIM=0V, over 50ms — 35 50 μA VDIM_LH DIM High Threshold VIN=9V to 30V — — 2.4 V VDIM_HL DIM Low Threshold VIN=9V to 30V 0.6 — — V RPD_DIM DIM Internal Pull Down Resistance — — 500 — kΩ fDIM Dimming Frequency DIM pin 100 — 1000 Hz fDUTY Dimming Duty Cycle DIM pin 0 — 100 % TSHD Shutdown Mode Entry Period DIM=0V (Figure1) — 50 — ms TRT Recovery Time from Shutdown Mode DIM from "L" to "H" (Figure1) — 30 — ms Dimming Boost Converter fSW Switching Frequency — 175 200 225 kHz DMAX Maximum Duty Cycle — — 95 97.5 % VDRV(CLAMP) DRV Clamp Voltage VIN=24V — 13 14.5 V tr_DRV DRV Rise Time C=0.5nF — 40 — ns tf_DRV DRV Falling Time C=0.5nF — 20 — ns tLEB LEB Time of Current Sense Lead-Edge Blanking — 200 — ns — 200 — mV/ms Protections SRSS Soft Start Slope SS VOVP Output Over Voltage Detect Threshold VOVP ERROVP Tolerance of VOVP VUVLO+ Input Supply Turn ON Level VUVLO– Input Supply Turn OFF Level VOSP Output Short Circuit Threshold OSP VOCP Over Current Protection Threshold VSHORT LED Short Protection Threshold — 1.938 — V -5.0 — +5.0 % UVLO (on) — — 8.5 V UVLO (off) 6 — — V 0.05 0.1 — V OCP, V(CS) — 0.5 0.65 V LED Short, V(FB) — 1.2 1.56 V — 70 — mV — 150 — °C — VSHORT_HYS LED Short Protection Hysteresis THSHD Rev. 1.00 Thermal Shutdown — OTP 3 August 14, 2015 HT7963 Symbol Parameter Test Condition Min. Typ. Max. Unit — — 30 — °C — 0.3 — V — -3.0 — +3.0 % THSHD_HYS Hysteretic Temperature LED Output Current VFB Current Feedback Sensing Voltage ERRFB Tolerance of VFB DIM VFB 50ms, TSHD Shutdowm mode 30ms TRT IOUT Figure1 Functional Description Current Limiting The device has a cycle-by-cycle current limit to protect the external power MOSFET. If the inductor current reaches the current limit threshold, which is when the CS pin voltage is greater than 0.5V, the external MOSFET will be switched off. The Rcs value can be calculated from the following formula: General Operation The device is an LED driver operating as a DCDC boost converter in a constant frequency mode. It implements a peak current mode control and has an internal amplifier to accurately control the output current over conditions of wide input voltage and varying load. ILIMIT = Soft Start – SS Dimming Control The device has dedicated protection circuitry running during normal operation. The Soft Start function is set to have an internal time of around 5ms and is used to prevent a large inrush current during the power-on period. The LED brightness control is implemented using a PWM signal on the DIM pin. The PWM duty cycle is proportional to the dimming value. The device can apply an external PWM signal on the DIM pin with a frequency range from 100Hz to 1kHz with the required high/low ratio. Output Gate Drive Stage Output Over Voltage Protection – OVP A CMOS buffer output stage is included to drive a power MOSFET directly. The output voltage is clamped at 13V to protect the MOSFET gate even when the VCC voltage is higher than 13V. The device ����������������������������������������� includes��������������������������������� an������������������������������ ����������������������������� over-voltage protection function. In abnormal conditions, the output voltage may exceed its maximum voltage rating, possibly damaging external components and the LEDs. Protection circuitry turns off the power MOSFET and shuts down the device as soon as the output voltage exceeds the VOVP threshold. As a result, the output voltage falls to the level of the input supply voltage. The device remains in ���������������������������������������� the ������������������������������������ shutdown mode until the power is recycled. The VOUT_OVP value can be calculated from the following formula: Input Under Voltage Lockout – UVLO The device contains an input under-voltage lockout circuit. The purpose of the UVLO circuit is to ensure that the input voltage is high enough for reliable operation. When the input voltage falls below the under voltage threshold, the external FET switch is switched off. If the input voltage rises ���������������������� beyond���������������� the under voltage lockout hysteresis value, the device will restart. The UVLO threshold is set below the minimum input voltage of 6V to avoid any transient VIN drops under the UVLO threshold which may cause the converter to switch off. Rev. 1.00 0.5V RCS VOUT_OVP = 1.938V × R1+R2 R2 Output Short Protection – OSP An output short condition is detected by the voltage on pin OVP. In the period during the fault, if the voltage on the OVP pin drops by less than a threshold of around 0.1V, then the output short protection will be activated and the power MOSFET will be switched off. 4 August 14, 2015 HT7963 Thermal Shutdown MOSFET A thermal shutdown function is implemented to prevent damage due to excessive heat and power dissipation. Typically the thermal shutdown threshold is 150°C. When the thermal shutdown is triggered the device stops switching until the temperature falls below a typical temperature of 125°C, after which the device will again begin operation. Component Selection Guide It is recommended to use a MOSFET with small on resistance to minimi����������������������������������� s���������������������������������� e the power����������������������� ���������������������� dissipation and therefore to maximise the converter efficiency. MOSFETs with small gate capacitance values need to be selected to have high-speed switching. The maximum voltage rating of the MOSFET should be higher than the sum of VOUT and the rectifying diode VF. The maximum current rating must be greater than the over current protection setting and peak inductor current to ensure the best reliability in most applications. Inductor Input Capacitor The selected inductor should have a saturation current that meets the maximum peak current of the converter. Another important inductor parameter is the dc resistance. Lower dc resistance values results in higher converter efficiencies. For most applications, the inductor value can be obtained as below. A low ESR ceramic capacitor is required to be connected between the VIN and GND pins. Use ceramic capacitors with X5R or X7R dielectrics for their low ESRs and small temperature coefficients. This capacitor must be connected very close to the VIN pin and the inductor with short traces for good noise performance. L= VIN × (VOUT - VIN) ∆IL × fSW × VOUT Output Capacitor A higher value of ripple current reduces the inductance value, but increases the conductance loss, core loss and current stress for the inductor and switching devices. A suggested choice is for the inductor ripple current to be 30% of the maximum load current. This requires that the inductor saturation current be above IL(PEAK) . IIN(MAX) = A low ESR ceramic capacitor is suggested for use here as it will result in lower output ripple voltages. The selection of output capacitor is driven by the maximum allowable output voltage ripple. A ceramic capacitor with a low ESR value will provide the lowest voltage ripple and is therefore recommended. A capacitance in the range of 33μF to 47μF is sufficient. Capacitor voltage ratings needs to be selected to have an adequate margin against the highest output voltage. VOUT × IOUT(MAX) VIN × η ∆IL = 30% × IIN(MAX) LED Current Selection 1 IL(PEAK) = IIN(MAX) + ∆IL 2 The LED current is controlled by the current sense feedback resistor RFB, The current sense feedback reference voltage (VFB)���������������������������������� is ������������������������������ 0.3��������������������������� V. In order to ������������ obtain������ accurate LED currents, precision resistors are the preferred type with a 1% tolerance. The LED current (ILED) can be calculated from the following formula. IOUT(MAX) is the maximum load current, ΔIL is the peakto-peak inductor ripple current, η is the converter efficiency, fSW is the switching frequency and IL(PEAK) is the peak inductor current. Schottky Diode ILED = It is recommended to use a Schottky diode with low forward voltage to minimise the power dissipation and therefore to maximise the converter efficiency. The breakdown voltage rating of the diode should be higher than the maximum output voltage. The average and peak current rating must be greater than the maximum output current and peak inductor current to ensure the best reliability in most applications. Rev. 1.00 VFB 0.3V = RFB RFB CS Pin and FB Pin RC Filter Whether an RC low pass filer is employed or not depends upon the design layout and must be considered on a case-by-case basis. 5 August 14, 2015 HT7963 Layout Considerations Circuit board layout is a very important consideration for switching regulators if they are to function properly. Poor circuit layout may result in related noise problems. In order to minimise EMI and switching noise, the following guidelines should be adhered to: • All tracks should be as wide as possible • The input and output capacitors, CIN and COUT, should be placed close to the VIN, VOUT and GND pins • The Schottky diode, D1, and inductor, L, must be placed close to the power MOSFET drain • Feedback resistor, RFB, must be placed close to the FB and GND pins • A full ground plane is always helpful for better EMI performance A recommended PCB layout with component locations is shown below. 57mm 35mm Top Layer Rev. 1.00 Bottom Layer 6 August 14, 2015 HT7963 Typical Performance Characteristics Fig.2 Feedback Voltage VS Temperature Fig.5 Frequency VS Temperature Fig.3 CS Protection Voltage VS Temperature Fig.6 Operating Current VS Temperature Fig.4 FB Protection Voltage VS Temperature Fig.7 OVP Protection Voltage VS Temperature Rev. 1.00 7 August 14, 2015 HT7963 Dimming Linearity Fig.8 VIN=12V, LED=16S5P, VOUT=44.5V, IOUT=453mA, Fig.9 VIN=12V, LED=16S5P, VOUT=45.8V, IOUT=719mA, COUT=47μF, POUT=20W (Ta=25°C) COUT=47μF, POUT=33W (Ta=25°C) Fig.10 VIN=24V, LED=30S5P, VOUT=81.5V, IOUT=245mA, Fig.11 VIN=24V, LED=30S5P, VOUT=84.3V, IOUT=602mA, COUT=47μF, POUT=20W (Ta=25°C) COUT=47μF, POUT=50W (Ta=25°C) Fig.12 VIN=30V, LED=40S5P, VOUT=106.8V, Fig.13 VIN=30V, LED=40S5P, VOUT=110.5V, IOUT=188mA, COUT=47μF, POUT=20W (Ta=25°C) IOUT=451mA, COUT=47μF, POUT=50W (Ta=25°C) Rev. 1.00 8 August 14, 2015 HT7963 Package Information Note that the package information provided here is for consultation purposes only. As this information may be updated at regular intervals users are reminded to consult the Holtek website for the latest version of the Package/ Carton Information. Additional supplementary information with regard to packaging is listed below. Click on the relevant section to be transferred to the relevant website page. • Further Package Information (include Outline Dimensions, Product Tape and Reel Specifications) • Packing Meterials Information • Carton information Rev. 1.00 9 August 14, 2015 HT7963 8-pin SOP (150mil) Outline Dimensions Symbol A Dimensions in inch Min. Nom. Max. — 0.236 BSC — B — 0.154 BSC — C 0.012 — 0.020 C' — 0.193 BSC — D — — 0.069 E — 0.050 BSC — F 0.004 — 0.010 G 0.016 — 0.050 H 0.004 — 0.010 α 0° — 8° Symbol Rev. 1.00 Dimensions in mm Min. Nom. Max. A — 6.00 BSC — B — 3.90 BSC — C 0.31 — 0.51 C' — 4.90 BSC — D — — 1.75 E — 1.27 BSC — F 0.10 — 0.25 G 0.40 — 1.27 H 0.10 — 0.25 α 0° — 8° 10 August 14, 2015 HT7963 Copyright© 2015 by HOLTEK SEMICONDUCTOR INC. The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holtek's products are not authorized for use as critical components in life support devices or systems. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw. Rev. 1.00 11 August 14, 2015