RT8129AGQW

RT8129A High Efficiency Single Synchronous Buck PWM Controller General Description Features The RT8129A is a high efficiency single phase synchronous buck controller with 5V/12V supply voltage. The RT8129A integrates a Constant-On-Time (COT) PWM controller and a MOSFET drivers with internal bootstrap diodes, which is specifically designed to improve converter efficiency at light load condition. At light load condition, it automatically operates in the diode emulation mode to reduce switching frequency and improve conversion efficiency. Other features include power good indication, enable/disable control and internal soft-start function. The RT8129A also provide protection functions including Over Voltage Protection (OVP), Under Voltage Protection (UVP), current limit and thermal shutdown. This device uses lossless low-side MOSFET RDS(ON) current sense technique for current limit with adjustable threshold set by connecting a resistor between the LGATE/OCSET and GND. With above functions, the RT8129A  Wide Input Voltage Range : 2.5V to 25V  High Light Load Efficiency  Integrated High Driving Capability N-MOSFET Gate  Drivers and Embedded Switching Boot Diode         Single IC Supply Voltage : 4.5V to 13.2V Power-Good Indicator Enable/Disable Control Internal Soft-Start Programmable Current Limit Threshold Under Voltage Protection Over Voltage Protection Thermal Shutdown Applications    Motherboard, Memory/Chip-set Power Graphic Card, GPU/Memory Core Power Low Voltage, High Current DC/DC Regulator Marking Information provides customers a cost-effective solution for high efficiency power conversion. The RT8129A is available in the WDFN-10L 3x3 package. 5N=YM DNN 5N= : Product Code YMDNN : Date Code Simplified Application Circuit VIN RT8129A VCC VCC BOOT UGATE PHASE VPGOOD PGOOD VOUT LGATE/ OCSET EN Enable FB GND Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS8129A-01 October 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8129A Ordering Information Pin Configurations RT8129A Lead Plating System G : Green (Halogen Free and Pb Free) Note : Richtek products are :  BOOT PHASE UGATE LGATE/OCSET GND 1 2 3 4 5 GND (TOP VIEW) Package Type QW : WDFN-10L 3x3 (W-Type) 11 10 9 8 7 6 PGOOD NC FB EN VCC WDFN-10L 3x3 RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.  Suitable for use in SnPb or Pb-free soldering processes. Functional Pin Description Pin No. Pin Name Pin Function BOOT Bootstrap Supply for High Side Gate Driver. Connect this pin to a power source VCC through a bootstrap diode, and connect a 0.1F or greater ceramic capacitor from this pin to the PHASE pin to supply the power for high side gate driver. 2 PHASE Switch Node. Connect this pin to the switching node of Buck converter. Connect this pin to the Source of high-side MOSFET together with the Drain of low-side MOSFET and the inductor. The PHASE voltage is sensed for zero current detection and over current protection when low side MOSFET is on. 3 UGATE High Side MOSFET Gate Driver Output. This pin provides the gate drive for the converter's high-side MOSFET. Connect this pin to the Gate of high-side MOSFET. 4 Low Side MOSFET Gate Driver Output. Connect this pin to the Gate of low side MOSFET. This pin is also used for current limit threshold setting. LGATE/OCSET Connect a resistor (ROCSET) from this pin to the GND pin to set the current limit threshold. 1 5, GND 11 (Exposed Pad) Ground. The Exposed Pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 6 VCC Supply Voltage Input. It is recommended to connect a 4.7F ceramic capacitor from this pin to the GND pin. VCC also powers the low side gate driver. 7 EN Enable Control Input. Drive EN higher than 2V to turn on the controller, lower than 0.8V to turn it off. If the EN pin is open, it will be pulled to high by internal circuit. 8 FB This pin is used for output voltage feedback input and it is also monitored for power good indication, over voltage and under voltage protections. Connect this pin to the converter output through voltage divider resistors for output voltage regulation. 9 NC No Internal Connection. PGOOD Power Good Indication Output. This pin provides an open drain output. Connect this pin to a voltage source through a pull up resistor. The PGOOD voltage goes high to indicate the output voltage is in regulation. This pin can be left open if the power good indication function is not used. 10 Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8129A-01 October 2015 RT8129A Function Block Diagram Trigger TON Generator 1-Shot VREF PHASE BOOT + R COMP S - + 125% VREF 75% VREF PGOOD + PGOOD Monitor ±10% VREF LDO& POR VCC EN UV Latch S1 Q - FB OV Latch S1 Q Thermal Shutdown PHASE Min TOFF 1-Shot Trigger VCC LGATE/OCSET GND ASM 10µA + SS REF UGATE Q - + gm - Sample and Hold VREF Operation The RT8129A integrates a Constant-On-Time (COT) PWM controller and MOSFET driver so that the external circuit is easily designed and the components are reduced. The controller provides the PWM signal which relies on the FB voltage comparing with internal reference voltage. The synchronous UGATE driver is turned on at the beginning of each cycle. After the internal one-shot timer expires, the UGATE driver will be turned off. The pulse width of this one-shot is determined by the controller's input voltage and the output voltage to keep the frequency fairly constant over the input voltage and output voltage range. Another one-shot sets a minimum off-time. The RT8129A remains in shutdown if the EN pin voltage is lower than 0.8V. When the EN pin voltage rises above the2V, the RT8129A will begin a new initialization and soft-start cycle. PGOOD The power good output is an open-drain architecture, and it requires a pull-up resistor. During soft-start Copyright © 2015 Richtek Technology Corporation. All rights reserved. October Soft-Start An internal current source charges an internal capacitor to build the soft-start ramp voltage. The output voltage will track the internal ramp voltage during soft-start interval. The typical soft-start time is 2ms. Current Limit Enable DS8129A-01 process, PGOOD is actively held low and is allowed to be pulled high after soft start process is completed and no protection occur. In addition, if the FB pin voltage is higher than 110% of VREF or lower than 90% of VREF during operation, PGOOD will be pulled low immediately. 2015 The current limit circuit employs a unique “valley” current sensing algorithm. If the magnitude of the current sense signal at PHASE is above the current limit threshold, the PWM is not allowed to initiate a new cycle. Thus, the current to the load exceeds the average output inductor current, the output voltage falls and eventually crosses the under-voltage protection threshold, inducing IC shutdown. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8129A Over Voltage Protection (OVP) Under Voltage Protection (UVP) The FB voltage can be continuously monitored for over voltage protection. When the FB voltage exceeds The output voltage can be continuously monitored for under voltage protection. When the FB voltage is less 125% of the reference voltage, UGATE goes low and LGATE is forced high. The controller is latched until VCC is re-supplied and exceeds the POR rising threshold voltage. than 75% of the reference voltage, under voltage protection is triggered and then both UGATE and LGATE gate drivers are forced low. The controller is latched until VCC or EN pin voltage is re-supplied and exceeds the POR rising threshold voltage. There is a 5s delay built into the under voltage protection circuit to prevent false transitions. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 There is a 3s delay built into the under voltage protection circuit to prevent false transitions. is a registered trademark of Richtek Technology Corporation. DS8129A-01 October 2015 RT8129A Absolute Maximum Ratings (Note 1)  VCC to GND ------------------------------------------------------------------------------------------------------------ 0.3V to 15V  Other Pins --------------------------------------------------------------------------------------------------------------- 0.3V to 6.5V  BOOT to PHASE DC--------------------------------------------------------------------------------------------------------------------------0.3V to 15V