LD7835 LEADTREND | Alldatasheet
Document overview
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Technical content
Features
High Power Factor Controller Integrated High Efficiency Transition Mode Operation Good Accurate Current Regulation Current Ripple Reduction (CRR) Function Wide Range of UVLO Built in OVP on VCC pin LED Open Protection LED Short Protection OCP (Cycle by cycle current limit) OTP (Over Temperature Protection) 250mA/-250mA Driving Capability
Applications
LED Lamp、LED bulb Application Typical Application GATE COMP VCC ZCD Rs GND EMI Filter AC Input CS RUP RDOWNLD7835 RF (Option) CF (Option) Fig. 1 Application circuit
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 Pin Configuration SOT-26 (TOP VIEW) YY, Y : Year code (D: 2004, E: 2005…..) WW, W : Week code PP : Production code S35 : LD7835 1 2 3 4 5 6 COMP GND ZCD CS OUT VCC YWS 35 pp
Ordering Information
Part number Package Top Mark Shipping LD7835 GL SOT-26 YWS/35 3000 /tape & reel The LD7835 is ROHS compliant/ green packaged. Pin Descriptions Pin NAME FUNCTION
1 COMP Compensation pin for internal error amplifier
2 GND Ground
3 ZCD
Over voltage protection setting, Quasi resonance detector, support programmable maximum on-time.
4 VCC Power Supply to VCC
5 OUT Gate Signal Output
Connecting a sense resistor to ground, support CRR function setting.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 Block Diagram CSLEB PWM Comparator R S OCP 0.6V/1V Ramp Generator 1.2V Comparator COMP Q gm Fmax Limit Time Out Vref ZCD Driver Stage UVLO (ON)/ (OFF) UVLO Comparator internal bias & VREF VREF OK VCC OK All Block VCC VOVP /28V VCC OVP VCC OVP R S Q GND FB PG ZCD OVP PG Max On Limit OUT
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 Absolute Maximum Ratings VCC -0.3V ~ 30V CS -1V ~ 6V ZCD -0.3V ~ 6V COMP -0.3V ~ 6V ZCD Source/ Sink Current -2mA ~ 1mA OUT -0.3V ~ 30V Operating Junction Temperature 150C Storage Temperature Range -65C to 150C Package Thermal Resistance (SOT-26, JA) 200C/W Power Dissipation (SOT-26, TJ=125oC, TA=85C) 200mW Lead temperature (Soldering, 10sec) 260C ESD Voltage Protection, Human Body Model 2.5KV ESD Voltage Protection, Machine Model 250 V Caution: Stress exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stress above Recommended Operating Conditions may affect device reliability. Recommended Operating Conditions Item Min. Max. Unit VCC 13 24 V VCC pin capacitor 4.7 22 F COMP 0.8 5 V COMP pin capacitor 0.47 2.2 F Operating Junction Temperature Range -20 125 C Note: 1. It’s essential to connect VCC pin with a SMD ceramic capacitor (0.1 F~0.47F) to filter out the undesired switching noise for stable operation. This capacitor should be placed close to IC pin as possible 2. Connecting a capacitor to COMP pin is also essential to filter out the undesired switching noise for stable operation. 3. The small signal components should be placed close to IC pin as possible.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015
Electrical Characteristics
( VCC =14.0V, TA = 25C unless otherwise specified.) PARAMETER CONDITIONS Symbol MIN TYP MAX UNITS Supply Voltage (VCC Pin) Startup Current VCC=10V IVCC_ST - - 10 A Operating Current (with 1nF load on OUT pin) COMP=3V, ZCD=2V IVCC_14 - 1 - mA Protection Tripped (OVP, OTP) IVCC_PRO - 2 - mA UVLO (OFF) VUV_OFF 7.7 8.2 8.7 V UVLO (ON) VUV_ON 15 16 17 V VCC OVP Threshold VCC_OVP 27 28 29 V Compensation(COMP Pin) COMP Pin Open Voltage VCMP 5 5.5 6 V Programmable Max-On Time Level 1, COMP =5V TON_MAX1 - 15 - s Level 2, COMP =5V TON_MAX2 - 21 - s Level 3, COMP =5V TON_MAX3 - 29 - s Pre-charge voltage during soft-start(1) VCMP_PRE - 0.6 - V Current Sensing (CS Pin) Reference voltage Vref 0.194 0.2 0.206 V OCP Threshold (Cycle by Cycle) VOCP 1.1 1.2 1.3 V During soft-start VOCP_SS - 0.45 - V Soft-Start Time TSS 12 16 20 ms LEB time TLEB - 250 - ns Zero Current Detector (ZCD Pin) Lower Clamp Voltage VZCD_LC - 0 - V ZCD OVP Threshold VZCD_OVP 3.8 4 4.2 V ZCD OVP Comparator De-bounce TDEB_OVP - 1.6 - s Input Voltage Threshold VZCD - 0.6 - V Hysteresis VZCD_HYS - 0.4 - V ZCD Blanking Time TZCD_BLK 1.5 2 2.5 s Minimum (ON+OFF)-Time, FMAX Minimum ON+OFF-Time FS, MAX(150kHz) TMIN 5.34 6.67 8 s During Soft-Start TMIN_SS - 11 - s
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 PARAMETER CONDITIONS Symbol MIN TYP MAX UNITS Gate Drive Output (OUT Pin) Output Low Level VCC=15V, ISINK=20mA VOUT_L - - 0.5 V Output High Level VCC=15V, ISOURCE=5mA VOUT_H 8 - VCC V Output High Clamp Level VCC=15V VOUT_CL 12 13 14 V Rising Time(1) VCC=15V, CL=1nF - - 120 - ns Falling Time(1) VCC=15V, CL=1nF - - 30 - ns Time out Time out Period during Soft start TOUT_SS - 80 - s Time out Period after soft start TOUT 120 160 200 s OTP (Over Temp. Protection) OTP Trip level(1) - - 140 - C OTP Hysteresis(1) - - 30 - C Note: (1) Guaranteed by Design.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 Typical Performance Characteristics UVLO (ON) (V) Fig. 2 UVLO (ON) vs. Temperature Temperature (C) 15.0 15.5 16.0 16.5 17.0 17.5 -40 0 40 80 120 125 UVLO (OFF) (V) Temperature (C) Fig. 3 UVLO (OFF) vs. Temperature 7.6 8.0 8.2 8.6 7.8 -40 0 40 80 120 125 8.4 Operating Current (mA) Temperature (C) Fig. 4 Operating Current vs. Temperature -40 0 40 80 120 125 1.05 1.10 1.15 1.20 1.25 1.00 Start-up Current (uA) Temperature (C) Fig. 5 Start-up Current vs. Temperature -40 0 40 80 120 125 OCP Threshold (V) Temperature (C) Fig. 6 OCP Threshold vs. Temperature 1.10 1.15 1.20 1.25 1.30 1.35 -40 0 40 80 120 125 Reference Voltage (V) Temperature (C) Fig. 7 Reference Voltage vs. Temperature -40 0 40 80 120 125 0.18 0.19 0.20 0.21 0.22 0.17
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 ZCD OVP Threshold (V) Temperature (C) Fig. 8 ZCD OVP Threshold vs. Temperature -40 0 40 80 120 125 3.95 4.00 4.05 4.10 4.15 3.90 VCC OVP Threshold (V) Temperature (C) Fig. 9 VCC OVP Threshold vs. Temperature 27.0 27.5 28.0 28.5 29.0 29.5 -40 0 40 80 120 125 COMP Pin Open Voltage (V) Temperature (C) Fig. 10 COMP Pin Open Voltage vs. Temperature -40 0 40 80 120 125 5.0 5.2 5.4 5.6 5.8 6.0 Time out (us) Temperature (C) Fig. 11 Time out vs. Temperature -40 0 40 80 120 125 120 140 160 180 200 100 Max-On Time1 (us) Temperature (C) Fig. 12 Max-On Time1(COMP=5V) vs. Temperature -40 0 40 80 120 125 ZCD Input Threshold (us) Temperature (C) Fig. 13 ZCD Input Threshold vs. Temperature -40 0 40 80 120 125 0.58 0.60 0.62 0.64 0.66 0.56
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015
Application Information
LD7835 is an LED controller for lighting application. The transition mode (TM) technique meets the requirements for high power factor and high efficiency. It minimizes the external component counts and the PCB size for compact application. The control mechanism of LD7835 is a voltage -mode operation. The switch turn -on time is fixed while the turn-off time varies in steady state. Therefore, the switch frequency changes in response to the different voltages. The affected frequency reduces EMI noise. LD7835 also features LED open protection, LED short protection, over current protection, and over temperature protection. No extra mains voltage sensing is required as what the traditional current mode PFC controllers behaves for power saving. Ramp Generator Block, Zero Current Detection (ZCD) and ZCD OVP Fig. 14 shows typical ramp generator block and ZCD block. The COMP pin voltage and the output of the ramp generator block are compared to determine the MOSFET On-time, as shown in Fig. 15. The LD7835 features transition mode (TM) operation. The zero current detection block circuit detects the ZCD signal to turn on the MOSFET soon after the voltage across ZCD falls to 0.6V and also the current through the inductor reaches zero. Instead, if there’s no signal detected within 160 s, t he time -out will generate a signal to turn on MOSFET to ensure the system operate properly. PWM Comparator R S 0.6V/1V Ramp Generator 1.2VOCP ComparatorCOMP Q GM Fmax Limit Time Out Vref ZCD FB Max On Limit CS Fig. 14 During the delay time as shown in Fig. 15, the junction capacitor of the MOSFET resonates with the inductor and the drain-source voltage (VDS) decreases accordingly. So, the MOSFET consumes less voltage and the power dissipation will be minimized. IPEAK TON TDIS Inductor Current Inductor Voltage VDS -(VIN-VOUT) Delay Time VOUT VIN Minimum Voltage Turn-on OUT VCMP RAMP ZCD Voltage 0.6V Rdown/(Rup+Rdown) ∙VOUT Fig. 15 Fig. 16 illustrates the operation of over voltage protection, where ZCD divider resist ors continue to detect the output voltage as the gate switches in off state and return the information to ZCD. If the output voltage increases to trip the threshold, it will signal that there may be some LED(s) open. The LD7835 will
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 then discharge VCC wit h a souring current (I CC_PRO) till VCC drops to UVLO (OFF) level. LD7835 will shut down its operation until VCC rises up to next UVLO (ON) level. If the open situation remains still, the system will enter to hiccup mode. 𝑉𝑍𝐶𝐷_𝑂𝑉𝑃 = 𝑉𝑂𝑉𝑃 × 𝑅𝐷𝑂𝑊𝑁 𝑅𝑈𝑃 +𝑅𝐷𝑂𝑊𝑁 ZCD t ZCD OVP Tripped t OUT Switching Switching Non-Switching Output Voltage t VCC t LED Opened Vout UVLO(ON) UVLO(OFF) OVP Level Fig. 16 Programming Maximum ON-time LD7835 features adjustable maximum ON -time to limit power output in abnormal operation. The selection of maximum ON -time is subject to ZCD resistance as shown in Fig. 17. ZCD resistance can be obtained from below: ZCD RUP RDOWN 𝑅𝑍𝐶𝐷 𝑅𝑈𝑃 ×𝑅𝐷𝑂𝑊𝑁 𝑅𝑈𝑃 +𝑅𝐷𝑂𝑊𝑁 Fig. 17 The following table is a suggestion for maximum ON-time setting. RZCD (Ω) Max. Ton (Typ.) Suggestion (Ω) 44k<RZCD 15s 46k 28k<RZCD<32k 21s 30k RZCD<20k 29s 18k Current Ripple Reduction (C.R.R) Function LD7835 features current ripple reduction function to minimum the output capacitor. The C.R.R rate is subject to RF resistance as shown in Fig. 1. The following table is a suggestion for CRR rate setting. RF (Ω) CRR Effective Rate Suggestion (Ω) 16k<RF Heavy 18k 7k<RF<8k Light 7.5k RF<0.2k Disable 0 The C.R.R effect is dependent on C .R.R rate, AC line and R UP in fixed output capacitance as shown in the following table for tuning reference. C.R.R Rate AC Line Rup Current Ripple Disable NA NA Original Light ↓ ↑ Lightest Heavy ↑ ↓ Heaviest If C.R.R function is enabled, the output capacitance and the saturation knee point of inductor can be minimize . However, power factor and THD will be slightly lower than disabled condition. It’s a trade -off factor between power factor and current ripple. LED Short Protection If some LED is in short condition, VCC will drop to UVLO (OFF) level and disable the LD7835. The LD7835 will not resume operation until VCC rises up to next UVLO (ON) level. If the short condition remains still, the system will enter to hiccup mode.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015 Over Current Protection (OCP) The LD7835 detects the MOSFET current from the CS pin, which is for the pulse -by-pulse current limit and output current feedback. The maximum voltage threshold of the CS pin is set at 1.2V. From above, the MOSFET peak current can be obtained from below. 𝑃𝐸 = 𝑉 𝑅 Over Voltage Protection (VCC OVP) The maximum rating of the VCC pin is limited below 30V. To prevent VCC from damage due to fault condition, the LD7835 is implemented with OVP function on VCC pin , this value is about 28V . As soon as the VCC voltag e is over OVP threshold voltage, the output gate drive circuit will be shutdown simultaneously thus to stop the switching of the power MOSFET until the next UVLO (ON) arrives. The VCC OVP function of the LD7835 is an auto -recovery protection. The Fig. 18 shows its operation. Upon removal of the OVP condition will resume the VCC level and the output operation VCC UVLO(ON) UVLO(OFF) t OVP Tripped t OUT Switching SwitchingNon-Switching OVP Level Fig. 18 Output Drive Stage An output stage of a CMOS buffer, with typical 250mA/-250mA driving capability, is incorporated to drive the power MOSFET directly. The output voltage is clamped at 13V to protect the MOSFET gate even when the VCC voltage rises over 13V.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015
Package Information
Dimension in Millimeters Dimensions in Inches Min Max Min Max A 2.692 3.099 0.106 0.122 B 1.397 1.803 0.055 0.071 D 0.300 0.500 0.012 0.020 F 0.95 TYP 0.037 TYP H 0.080 0.254 0.003 0.010 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 θ 0° 10° 0° 10° Important Notice Leadtrend Technology Corp. reserves the right to make changes or corrections to its products at any time without notice. Cust omers should verify the datasheets are current and complete before placing order.
Leadtrend Technology Corporation www.leadtrend.com.tw LD7835-DS-01 July 2015
Revision History
Rev. Date Change Notice 00 2014/08/28 Original Specification. 01 2015/07/29 Update equation of Fig 17.