LD7535 11/15/2005 Green-Mode PWM Controller with Integrated Protections Product Spec. (Rev. 00) General Description Features The LD7535 is a low cost, low startup current, current mode z PWM controller with green-mode power-saving operation. High-Voltage CMOS Process with Excellent ESD protection The integrated functions include the leading-edge blanking z Very Low Startup Current (<20µA) of the current sensing, internal slope compensation and the z Current Mode Control tiny package of SOT-26. It would provide the users a z Non-audible-noise Green Mode Control superior AC/DC power application of higher efficiency, low z UVLO (Under Voltage Lockout) external component counts, and lower cost solution for z LEB (Leading-Edge Blanking) on CS Pin applications. z Programmable Switching Frequency z Internal Slope Compensation z OVP (Over Voltage Protection) on Vcc Pin z OLP (Over Load Protection) z 300mA Driving Capability In comparing with the previous generations like LD755X, the LD7535 features more or functions for the following characteristics --z z Add OLP (Over Load Protection) function to provide better protection performance for fault conditions like Applications short circuit or over load. z Switching AC/DC Adaptor and Battery Charger z Open Frame Switching Power Supply z 384X Replacement Modify the OVP (Over Voltage Protection) mechanism from the cycle-by-cycle mode to the hiccup mode. Typical Application 1 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Pin Configuration SOT-26 (TOP VIEW) GND COMP NC RT DIP-8 (TOP VIEW) 8 7 6 5 TOP MARK OUT VCC CS 6 5 4 Y WP 35 1 2 3 GND COMP RT 1 2 3 4 OUT VCC NC CS YYWW## 6 5 Y WP 35 1 2 4 3 Y The PB freed package is identified in embossed font YY, Y : Year code (D: 2004, E: 2005…..) WW, W: Week code P : LD75.. (Product family code) ## : Production code Ordering Information Part number Package LD7535 IL LD7535 IN DIP-8 LD7535 BL SOT-26 (PB free) LD7535 BN DIP-8 (PB free) ( ) * TOP MARK SOT-26 YWP/35 LD7535IN ( ) * YWP/35 LD7535BN Shipping 3000 /tape & reel 3600 /tube /Carton 3000 /tape & reel 3600 /tube /Carton printed in different font Pin Descriptions PIN (SOT-26) NAME 1 GND 2 COMP 3 RT 4 CS FUNCTION Ground Voltage feedback pin (same as the COMP pin in UC384X), By connecting a photo-coupler to close the control loop and achieve the regulation. This pin is to program the switching frequency. By connecting a resistor to ground to set the switching frequency. Current sense pin, connect to sense the MOSFET current 5 VCC Supply voltage pin 6 OUT Gate drive output to drive the external MOSFET 2 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Block Diagram ∑ * Note: OLP delay is 60mS when the switching frequency is set as 65KHz. The OLP delay time is proportional to the period of switching cycle. That is, TOLP _ delay ∝ Ts = 1 . fs 3 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Absolute Maximum Ratings Supply Voltage VCC 30V COMP, RT, CS -0.3 ~7V Junction Temperature 150°C Operating Ambient Temperature -40°C to 85°C Storage Temperature Range -65°C to 150°C Package Thermal Resistance 250°C/W Power Dissipation (SOT-26, at Ambient Temperature = 85°C) 250mW Power Dissipation (DIP-8, at Ambient Temperature = 85°C) 650mW Lead temperature (SOT-26 & DIP-8, Soldering, 10sec) 230°C Lead temperature (All PB Free Packages, Soldering, 10sec) 260°C ESD Voltage Protection, Human Body Model 3KV ESD Voltage Protection, Machine Model 250V Gate Output Current 300mA Caution: Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not limited. Recommended Operating Conditions Item Min. Max. Unit Supply Voltage Vcc 11 25 V Switching Frequency 50 130 KHz 4 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Electrical Characteristics o (TA = +25 C unless otherwise stated, VCC=15.0V) PARAMETER CONDITIONS MIN TYP MAX UNITS 8 20 µA 2.0 3.0 mA Supply Voltage (Vcc Pin) Startup Current Operating Current (with 1nF load on OUT pin) VCOMP=0V VCOMP=3V 2.5 mA Protection tripped (OLP, OVP) 0.5 mA UVLO (off) 9.0 10.0 11.0 V UVLO (on) 15.0 16.0 17.0 V OVP Level 26.5 28.0 29.5 V 1.5 2.2 mA Voltage Feedback (Comp Pin) Short Circuit Current VCOMP=0V Open Loop Voltage COMP pin open Green Mode Threshold VCOMP 6.0 V 2.35 V Current Sensing (CS Pin) Maximum Input Voltage, Vcs(off) 0.80 Leading Edge Blanking Time 0.85 0.90 350 Input impedance nS 1 Delay to Output V MΩ 100 nS Oscillator (RT pin) Frequency RT=100KΩ Green Mode Frequency Fs=65KHz 60 65 70 20 KHz KHz Temp. Stability (-40°C ~105°C) 3 % Voltage Stability (VCC=11V-25V) 1 % Output Low Level VCC=15V, Io=20mA 1 V Output High Level VCC=15V, Io=20mA Rising Time Load Capacitance=1000pF 50 200 nS Falling Time Load Capacitance=1000pF 30 100 nS OLP Trip Level Vcomp(OLP) 5.0 V OLP Delay Time (note) Fs=65KHz 60 mS Gate Drive Output (OUT Pin) 8 V OLP (Over Load Protection) Note: The OLP delay time is proportional to the period of switching cycle. frequency and the shorter OLP delay time. 5 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 So that, the lower RT value will set the higher switching LD7535 18.0 12 17.2 11.2 UVLO (off) (V) UVLO (on) (V) Typical Performance Characteristics 16.4 15.6 9.6 8.8 14.8 14.0 10.4 8 -40 0 40 80 120 125 -40 125 26 Green Mode Frequency (KHz) Frequency (KHz) 120 Fig. 2 UVLO (off ) vs. Temperature 68 66 64 62 24 22 20 18 16 -40 0 40 80 120 125 40 120 125 80 Temperature (°C) Fig. 4 Green Mode Frequency vs. Temperature 25 Green Mode Frequency (KHz) 70 68 66 64 62 60 11 0 -40 Temperature (°C) Fig. 3 Frequency vs. Temperature Frequency (KHz) 80 Temperature (°C) 70 60 40 0 Temperature (°C) Fig. 1 UVLO (on) vs. Temperature 12 14 16 18 20 22 24 23 21 19 17 15 11 25 12 14 16 18 20 22 Vcc (V) Vcc (V) Fig. 5 Frequency vs. Vcc Fig. 6 Green Mode Frequency vs. Vcc 6 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 24 25 LD7535 85 0.90 0.88 VCS (off) (V) Max Duty (%) 80 75 70 65 0.86 0.84 0.82 60 -40 0 40 80 0.80 120 125 -40 Temperature (°C) 0 40 80 120 125 Temperature (°C) Fig. 8 VCS (off) vs. Temperature Fig. 7 Max Duty vs. Temperature 12 35 10 30 VCC OVP (V) Istartup (µA) 8 6 4 25 20 15 2 0 -40 10 0 40 80 120 125 -40 40 0 Temperature (°C) Fig. 10 Startup Current (Istartup) vs. Temperature 7.0 6.0 6.5 5.5 6.0 5.0 OLP (V) VCOMP (V) Fig. 9 5.5 5.0 4.5 80 120 125 120 125 Temperature (°C) VCC OVP vs. Temperature 4.5 4.0 -40 0 40 80 3.5 120 125 -40 0 Temperature (°C) Fig. 11 VCOMP open loop voltage vs. Temperature Fig. 12 7 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 40 80 Temperature (°C) OLP-Trip Level vs. Temperature LD7535 Application Information startup current requirement on the PWM controller will help Operation Overview to increase the value of R1 and then reduce the power The LD7535 meets the green-power requirement and is consumption on R1. By using CMOS process and the intended for the use in those modern switching power special circuit design, the maximum startup current of suppliers and adaptors which demand higher power LD7535 is only 20µA. efficiency and power-saving. It integrated more functions to reduce the external components counts and the size. Its If a higher resistance value of the R1 is chosen, it usually major features are described as below. takes more time to start up. To carefully select the value of R1 and C1 will optimize the power consumption and startup time. Under Voltage Lockout (UVLO) An UVLO comparator is implemented in it to detect the voltage on the VCC pin. It would assure the supply voltage enough to turn on the LD7535 PWM controller and further to drive the power MOSFET. As shown in Fig. 13, a hysteresis is built in to prevent the shutdown from the voltage dip during startup. The turn-on and turn-off threshold level are set at 16V and 10.0V, respectively. Vcc UVLO(on) UVLO(off) t I(Vcc) operating current (~ mA) Fig. 14 Current Sensing and Leading-edge Blanking startup current (~uA) The typical current mode of PWM controller feedbacks both t current signal and voltage signal to close the control loop Fig. 13 and achieve regulation. As shown in Fig. 15, the LD7535 detects the primary MOSFET current from the CS pin, which is not only for the peak current mode control but also for the Startup Current and Startup Circuit pulse-by-pulse current limit. The maximum voltage The typical startup circuit to generate the LD7535 is shown threshold of the current sensing pin is set at 0.85V. From in Fig. 14. During the startup transient, the Vcc is lower above, the MOSFET peak current can be obtained from than the UVLO threshold thus there is no gate pulse below. produced from LD7535 to drive power MOSFET. IPEAK(MAX) = Therefore, the current through R1 will provide the startup current and to charge the capacitor C1. Whenever the Vcc voltage is high enough to turn on the LD7535 and further to deliver the gate drive signal, the supply current is provided from the auxiliary winding of the transformer. Lower 8 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 0.85 V RS LD7535 350ns blanking time VCC OUT LD7535 CS Fig. 15 GND A 350nS leading-edge blanking (LEB) time is included in the input of CS pin to prevent the false-trigger from the current Can be removed if the negative spike is not over spec. (-0.3V). spike. In the low power application, if the total pulse width of Fig. 16 the turn-on spikes is less than 350nS and the negative spike on the CS pin doesn’t exceed -0.3V, it could eliminated the R-C filter (as shown in the figure16). However, the total pulse width of the turn-on spike is decided by the output power, circuit design and PCB layout. It is strongly recommended to adopt a smaller R-C filter (as shown in figure 17) for higher power application to avoid the CS pin being damaged by the negative turn-on spike. Output Stage and Maximum Duty-Cycle An output stage of a CMOS buffer, with typical 300mA driving capability, is incorporated to drive a power MOSFET directly. And the maximum duty-cycle of LD7535 is limited to 75% to avoid the transformer saturation. Oscillator and Switching Frequency Connect a resistor from RT pin to GND according to the equation below to program the normal switching frequency: fSW = 65.0 × 100(KHz ) RT(KΩ ) Fig. 17 The operating frequency range for the LD7535 is Voltage Feedback Loop recommended to set between 50KHz and 130KHz. The voltage feedback signal is provided from the TL431 at the secondary side through the photo-coupler to the COMP pin of the LD7535. Similar to UC3842, the LD7535 would carry 2 diodes voltage offset at the stage to feed the voltage divider at the ratio of 1/3, that is, 9 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 1 V−( PWM COMPARATOR ) = × (VCOMP − 2VF ) 3 A pull-high resistor is embedded internally and can be eliminated externally. Internal Slope Compensation In the conventional application, the problem of the stability is a critical issue for current mode controlling, when it operates in higher than 50% of the duty-cycle. As UC384X, It takes slope compensation from injecting the ramp signal of the ∑ RT/CT pin through a coupling capacitor. It therefore requires no extra design for the LD7535 since it has integrated it Fig. 18 already. The green-mode oscillator will detect the signal of COMP On/Off Control pin to determine if it meets the requirement of operation. The LD7535 can be turned off by pulling COMP pin lower than 1.2V. When the signal of V- is lower than the green-mode The gate output pin of the LD7535 will be threshold VGREEN, the green-mode oscillator will activate. disabled immediately under such condition. The off-mode The green-mode oscillator, implemented by a VCO (voltage can be released when the pull-low signal is removed. controlled oscillator), is a variable frequency oscillator. By using this dual-oscillator control, the green-mode Dual-Oscillator Green-Mode Operation frequency can be well controlled and further to avoid the There are many different topologies has been implemented generation of audible noise. in different chips for the green-mode or power saving requirements such as “burst-mode control”, “skipping-cycle OVP (Over Voltage Protection) on Vcc Mode”, “variable off-time control “…etc. The basic operation The VGS ratings of the nowadays power MOSFETs are often theory of all these approaches intended to reduce the limited up to max. 30V. To prevent the VGS from the fault switching cycles under light-load or no-load condition either condition, LD7535 is implemented an OVP function on Vcc. by skipping some switching pulses or reduce the switching Whenever the Vcc voltage is higher than the OVP threshold frequency. voltage, the output gate drive circuit will be shutdown What LD7535 uses to implement the power-saving operation is Leadtrend Technology’s own IP. simultaneously thus to stop the switching of the power In such MOSFET until the next UVLO(on). approaching, as shown in the block diagram, there are 2 The Vcc OVP function in LD7535 is an auto-recovery type oscillators are implemented in LD7535. The first oscillator is protection. to set the normal switching frequency, which can be set by the RT pin through an external resistor. In such operation the OVP level again and re-shutdown the output. mode, as shown in Fig. 18, the 2nd oscillation (green-mode is working as a hiccup mode. oscillator) does not activate. Therefore, the rising-time and level will get back to normal level and the output will automatically return to the normal operation. switching frequency. 10 LD7535-DS-00-PROMATE November 2005 The figure 19 shows its On the other hand, if the OVP condition is removed, the Vcc Under the normal operation, this oscillator will dominate the Leadtrend Technology Corporation The Vcc operation. the falling-time of the internal ramp will be constant to achieve good stability over all temperature range. If the OVP condition, usually caused by the feedback loop opened, is not released, the Vcc will tripped LD7535 Fig. 19 Over Load Protection (OLP) To protect the circuit from being damaged under over load condition or short condition, a smart OLP function is implemented in the LD7535. The figure 20 shows the Fig. 20 waveforms of the OLP operation. In this case, the feedback system will force the voltage loop proceed toward the Fault Protection saturation and then pull up the voltage on COMP pin There are several critical protections were integrated in the (VCOMP). Whenever the VCOMP trips up to the OLP threshold LD7535 to prevent the power supply or adapter from being 5V and stays longer than 60mS, the protection will activate damaged. Those damages usually come from open or short and then turn off the gate output to stop the switching of condition on the pins of LD7535. Under the conditions listed power circuit. The 60mS delay time is to prevent the false below, the gate output will turn off immediately to protect the trigger from the power-on and turn-off transient. power circuit --- By such protection mechanism, the average input power can be reduced to very low level so that the component temperature and stress can be controlled within the safe operating area. 11 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 y RT pin short to ground y RT pin floating y CS pin floating LD7535 Reference Application Circuit --- 10W (5V/2A) Adapter Schematic 12 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Reference Application Circuit --- 10W (5V/2A) Adapter BOM P/N Component Value Original P/N Component Value Note R1A N/A C1 22µF, 400V R1B N/A C2 10µF, 50V R2A 750KΩ, 1206 C4 1000pF, 1000V, 1206 R2B 750KΩ, 1206 C5 0.01µF, 16V, 0805 R4A 39KΩ, 1206 C51 1000pF, 50V, 0805 R4B 39KΩ, 1206 C52 1000µF, 10V L-tec R6 10Ω, 1206 C54 470µF, 10V L-tec R7 10Ω, 1206 C55 0.01µF, 16V, 0805 R8 10KΩ, 1206 CX1 0.1µF X-cap RS1 2.70Ω, 1206, 1% CY1 2200pF Y-cap RS2 2.70Ω, 1206, 1% D1A 1N4007 RT 100KΩ, 0805, 1% D1B 1N4007 R51A 100Ω, 1206 D1C 1N4007 R51B 100Ω, 1206 D1D 1N4007 R52 2.49KΩ, 0805, 1% D2 PS102R R53 2.49KΩ, 0805, 1% D4 1N4007 R54 220Ω, 0805 Q1 2N60B R55 10KΩ, 0805 CR51 SB540 R56A 510Ω, 1206 ZD51 6V2C R56B N/A IC1 LD7535 IL NTC1 08SP005 IC2 EL817B FL1 20mH IC51 TL431 T1 EI-22 F1 250V, 1A L51 2.7µH Z1 N/A UU9.8 13 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 L-tec Holystone 600V/2A SOT-26 1% LD7535 Reference Application Circuit #2 --- 10W Adapter with 2-Stage Startup Circuit Pin < 0.25W when Pout = 0W AC input F1 R1A R1B NTC1 Z1 FL1 RT 3 CX1 RT 5 VCC 6 4 D1A~D1D C1 IC1 2 1 GND LD7535 COMP R2A R7 D3 R2B C3 OUT CS R4A R4B C5 D2 R6 C2 R8 2-stage Startup Circuit D4 RS2 C4 T1 Q1 RS1 C51 C52 R56A ZD51 R54 C55 R55 L51 R56B R52 R53 C54 LD7535-DS-00-PROMATE November 2005 R51B R51A CR51 IC2 photocoupler CY1 IC51 14 Leadtrend Technology Corporation LD7535 Reference Application Circuit #2 --- 10W Adapter with 2-Stage Startup Circuit BOM P/N Component Value Original P/N Component Value Note R1A N/A C1 22µF, 400V L-tec R1B N/A C2 10µF, 50V L-tec R2A 2.2MΩ, 1206 C3 2.2µF, 50V R2B 2.2MΩ, 1206 C4 1000pF, 1000V, 1206 R4A 39KΩ, 1206 C5 0.01µF, 16V, 0805 R4B 39KΩ, 1206 C51 1000pF, 50V, 0805 R6 2.2Ω, 1206 C52 1000µF, 10V L-tec R7 10Ω, 1206 C54 470µF, 10V L-tec R8 10KΩ, 1206 C55 0.01µF, 16V, 0805 RS1 2.70Ω, 1206, 1% CX1 0.1µF X-cap RS2 2.70Ω, 1206, 1% CY1 2200pF Y-cap RT 100KΩ, 0805, 1% D1A 1N4007 R51A 100Ω, 1206 D1B 1N4007 R51B 100Ω, 1206 D1C 1N4007 R52 2.49KΩ, 0805, 1% D1D 1N4007 R53 2.49KΩ, 0805, 1% D2 PS102R R54 220Ω, 0805 D3 1N4148 R55 10KΩ, 0805 D4 1N4007 R56A 1KΩ, 1206 Q1 2N60B R56B N/A CR51 SB540 NTC1 5Ω, 3A 08SP005 ZD51 6V2C FL1 20mH UU9.8 IC1 LD7535 IL T1 EI-22 IC2 EL817B L51 2.7µH IC51 TL431 F1 250V, 1A Z1 N/A 15 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 Holystone 600V/2A SOT-26 1% LD7535 Package Information SOT-26 A θ M J B D C F I Dimension in Millimeters Dimensions in Inches Symbol Min Max Min Max A 2.692 3.099 0.106 0.122 B 1.397 1.803 0.055 0.071 C ------- 1.450 ------- 0.058 D 0.300 0.550 0.012 0.022 F 0.838 1.041 0.033 0.041 I 0.050 0.150 0.002 0.006 J 2.600 3.000 0.102 0.118 M 0.300 0.600 0.012 0.024 0 10 θ 0 ° 10 16 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 ° LD7535 Package Information DIP-8 A B E J C L I D F Dimension in Millimeters Dimensions in Inches Symbol Min Max Min Max A 9.017 10.160 0.355 0.400 B 6.096 7.112 0.240 0.280 C ----- 5.334 ------ 0.210 D 0.356 0.584 0.014 0.023 E 1.143 1.778 0.045 0.070 F 2.337 2.743 0.092 0.108 I 2.921 3.556 0.115 0.140 J 7.366 8.255 0.290 0.325 L 0.381 ------ 0.015 -------- Important Notice Leadtrend Technology Corp. reserves the right to make changes or corrections to its products at any time without notice. Customers should verify the datasheets are current and complete before placing order. 17 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005 LD7535 Revision History Rev. Date Change Notice P1 11/11/’05 Preliminary (Draft) 00 11/15/’05 1. Page 3, Correction on functional blocks by modifying the AND gate (following the PWM comparator) to OR gate. And add the description for the OLP delay time. 2. Page 5, Correction on OVP level for the typing error. The OVP tolerance range should be 26.5V~29.5V instead of 27.0V~29.0V. 3. Page 10, Correction on figure 18 and the (V+, V-) labeling to match with functional block. 18 Leadtrend Technology Corporation LD7535-DS-00-PROMATE November 2005