LD8926AA1 LEADTREND | Alldatasheet
Document overview
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Technical content
Features
Suited for low side and high side flyback synchronous rectification in CCM, DCM and QR(valley lock) mode Suited for forward freewheeling rectification in CCM and DCM Self-supplying for operation with low output voltage and/or high–side rectification without an auxiliary winding Suited for primary side with peak load function (max. frequency 130kHz) Suited for PD application, VCC range from 3V to 6V Programmable turn-off level Fast turn-off total delay of 30ns 200A ultra-low green mode operation current
Applications
Switching AC/DC adaptor and battery charger Open frame switching power supply
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Typical Application DC Output GND DET DRN VCC LD8926AA1 DRN 3
5 GND
Fig. 1 Flyback Low Side Synchronous Rectification GND DET DRN VCC LD8926AA1 DC Output DRN3 5GND DRN DRN Fig. 2 Flyback High Side Synchronous Rectification
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Pin Configuration GS: SOP-8 YY: Year code WW: Week code PP: Production code SOP-8 (TOP VIEW) 2 3 4 6 5 TOP MARK GSYYWWPP YYWWPP DET VCC GND GND DRN DRN DRN
7 DRN
Ordering Information
Part number Package Top Mark Shipping LD8926AA1 GS SOP-8 Green Package LD8926AA1 2500 / tape & reel The LD8926AA1 is ROHS compliant/ green packaged. Protection Mode Part number Int. OTP LD8926AA1 Auto-Restart Pin Description PIN NAME FUNCTION
1 DET Synchronous rectification detection
2 VCC Supply voltage pin
3~4 GND Ground pin 5~8 DRN MOS Drain Pin
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Block Diagram GND VCC Int. OTP DET VDET_OFF S Q R Minimum on/off time Green Mode Detect Driver Stage SR_ON Logic VBIAS IDET_OFF DRN LDO Int. DRV
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Absolute Maximum Ratings DET -1V ~ 200V DRN -0.3V ~ 100V VCC -0.3V ~ 7V DRN Continuous Current (at TC=25C/100C) 25A / 15A DRN Peak Current @ T=100us (at TC=25C/100C) 45A / 25A Maximum Junction Temperature 150C Storage Temperature Range -65C to 150C Package Thermal Resistance (SOP-8, JA) 106C/W Package Thermal Resistance (SOP-8, JC) 20C/W Power Dissipation (SOP-8, at Ambient Temperature = 85C) 377mW Lead temperature (Soldering, 10sec) 260C ESD Voltage Protection, Human Body Model (VCC) 2.5KV ESD Voltage Protection, Human Body Model (DET) 1KV ESD Voltage Protection, Human Body Model (DRN) 2.5KV ESD Voltage Protection, Machine Model 250V *Note1: The value of θJA is measured with the device mounted on 1 inch2 FR-4 board with 2oz. Copper, in a still air environment (Forced heat conduction K=3W/mK) with TA =25°C. The value in any given application depends on the user's specific board design. 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 implied. Recommended Operating Conditions Item Min. Max. Unit Operating Junction Temperature -40 125 C Supply Voltage VCC 3 6 V Operating Frequency 130 KHz VCC capacitor 2.2 F RDET 600 Ω Notes: 1. When MOSFET Ciss is the maximum value, turn-off RGATE must be the minimum value. On the contrary, when MOSFET Ciss is the minimum, turn-off RGATE must be the maximum.
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=5V) PARAMETER CONDITIONS SYMBOL MIN TYP MAX UNITS MOSFET drain (DRN Pin) Drain-Source Breakdown Voltage IDS=500µA BVDS 100 110 V Drain to Source On Resistance IDS=6A; VGS=4.5V RDS_ON 12 16 m Supply Voltage (VCC Pin) VCC UVLO (on) VCC_ON 2.8 3 3.2 V VCC UVLO (off) VCC_OFF 2.8 V UVLO Hysteresis VCC_HYS 0.2 V Operating Current VCC=5V, DET=65kHz IVCC_OP1 2 2.9 mA Green mode IVCC_OP2 200 250 µA Operating Current UVLO_OFF mode(option) VCC=2.5v IVCC_OFF 25 µA Detection Reference (DET Pin) Turn-on voltage VDET_ON -400 -300 -150 mV Turn-off voltage (2) VDET_OFF 10 20 30 mV Turn-off Compensation Current IDET_OFF 85 100 115 µA Ring Reject Threshold VDET_R 1.3 1.6 1.8 V Ring Reject Threshold Hysteresis VDET_RHY 1.1 V Ring Reject Window TDET_WD 50 70 100 ns Leakage Current VDET=200V IDET_LK 10 µA Max. Operating Limit (1) FSW_MAX 150 180 230 kHz On Chip OTP (Over Temperature) Auto-Recovery OTP Level (1) TOTP 150 C OTP Hysteresis (1) TOTP_HYS 30 C Notes: 1. Guaranteed by design. 2. For avoiding SR being too late to turn off in CCM, RDET must be adjusted from 600R down to appropriate value.
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Typical Performance Characteristics
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019
Application Information
The LD8926AA1 is a secondary side synchronous rectification driver IC for CCM and DCM operation. The LD8926AA1 not only has excellent dead time control function for safet y in load transie nt, but also only needs very low operation current in green mode. In addition, LD8926AA1 can generate its own supply voltage through low output voltage or high side rectification applications to charge battery. Hence, LD8926AA1 is suitable for PD application. To reduce assembly process, layout area, and production cost, SR MOSFET and LD8926AA1 control core are packaged in SOP-8. LDO Charge Function No matter LD8926AA1 is applied in high side or low side, there is a LDO (low drop -out regula tor) used to provide VCC power, and a capacitor must exist from VCC to GND to store the energy. Under Voltage Lockout (UVLO) and Enable Function An UVLO comparator is implemented to detect the voltage on the VCC pin. It will assure the supply voltage enough to turn on the LD8926AA1 controllers and further to drive the synchronous rectifier. As shown in Fig. 11, the UVLO(ON) and UVLO(OFF) are 3V and 2.8V respectively. To enable synchronous rectifier, the following conditions must be met: 1. VCC > UVLO(ON) 2. Exit green mode 3. DET > VDET_ON With these restrictions , synchronous rectifier always operates in stable condition. Therefore, some unstable transient, which are like turn -on, turn -off, output short, surge, ESD …etc., will not make synchronous rectifier unsafe when it works. UVLO(ON) UVLO(OFF) VCC Int. DRV t t DET t VDET_ON Fig. 11 Green Mode Operation For improving the efficiency in light load conditions , LD8926AA1 stops SR MOSFET driving function to reduce operation current, as shown in Fig. 12. DET pin detects system behavio r, and the internal logic circuit sets Int. DRV to high or low . Hence, LD8926AA1 can enter/exit green mode normally, even under dynamic load.
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 Pri. PWM Int. DRV t t >1.2ms 16cycle <1.1msGreen mode detection pulse Enter Green Mode Leave Green Mode Leave Green Mode >1.1ms <1.1ms Fig. 12 Turn-on Phase After a negative voltage (-300 mV typical) is sensed on the DET pin, the driver output voltage (Int. DRV, see Block Diagram) is made high and the internal MOSFET is switched on. After switch-on of the SR MOSFET, the input signal on the DET pin is blanked for 1.5s (typical). This will eliminate false switch-off due to high frequency ringing at the start of the secondary stroke. Turn-off Phase The DET pin has detection gate on time to do prediction gate pre-drop method (TON x 0.5 = TPREDICT), and adjusting VDS decreases gate driver voltage to 4V (typical). As soon as the DET voltage is above VDET_OFF, the driver output is pulled to ground. For avoiding SR being too late to turn off in CCM, the following condition must be met, as shown in Fig. 13. 10mV- X RI - V DETDET_OFFDET_OFF Where I DET_OFF = 100A, V DET_OFF = +20mV, X= thermal effect and parasitic inductance from trace & electronic components. Hence RDET must be from 600Ω down to find the appropriate turn-off time. The behavior of Int. DRV in DCM & CCM are shown separately in Fig. 14. DET Green Mode Detect SR_ ON Logic VBIAS SR_ MOS Drain RDET IDET_OFF VDET_OFF Fig. 13 ISD DET t t Int. DRV t ISD DET t t Int. DRV t VDET_OFF DCM CCM TPREDICT VDET_OFF TON TON TPREDICT Fig. 14 On-Chip OTP - Auto Recovery An internal OTP circuit is embedded inside the LD8926AA1 to provide the worst -case protection for this controller. When the chip temperature rises and is higher than the OTP trip level, the output will be disabled until the chip is cooled down below the hysteresis window. Recommended Layout Guide In order for the system to work properly, layout must pay attention to the following points: 1. Keep the DET and GND loops as small as possible. 2. The power loop needs to be separated from the DET detection loop.
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019 3. Place VCC capacitor as close to IC as possible. 4. Keep the GND of IC and the source pin of MOS as short as possible. 5. To let MOS be turned OFF in time, keep 5nH~20nH inductance of PCB trace as shown in Fig.15 & Fig. 16 in red lines. The suggested trace configurations are listed below: a. 3.5mm*18mm*2oz b. 4mm*20mm*2oz c. 3.5mm*9mm*1oz d. 4mm*10mm*1oz e. 6mm*15mm*1oz In high side application, DET detection point needs to be close to the output capacitor , and in low side application, DET detection point needs to be close to the transformer. Fig. 15 Fig. 16 GND DET DRN VCC LD8926AA1 DC Output DRN3 5GND DRN DRN DC Output GND DET DRN VCC LD8926AA1 DRN 3
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019
Package Information
Dimensions in Millimeters Dimensions in Inch MIN MAX MIN MAX A 4.801 5.004 0.189 0.197 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.178 0.254 0.007 0.010 I 0.102 0.254 0.004 0.010 J 5.791 6.198 0.228 0.244 M 0.406 1.270 0.016 0.050 θ 0° 8° 0° 8°
Leadtrend Technology Corporation www.leadtrend.com.tw LD8926AA1-DS-00 June 2019
Revision History
REV. Date Change Notice 00 06/14/2019 Original Specification 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.