SLUSDW9A June 2020 – June 2020 TPS51215A
PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Switch Mode Power Supply Control
- 7.3.2 VREF, V0, V1, V2, V3 and Output Voltage
- 7.3.3 Soft-Start and Power Good
- 7.3.4 SLEW and VID Function
- 7.3.5 MODE Pin Configuration
- 7.3.6 Light-Load Operation
- 7.3.7 Out-of-Bound Operation
- 7.3.8 Current Sensing and Overcurrent Protection
- 7.3.9 Overvoltage and Undervoltage Protection
- 7.3.10 V5IN Undervoltage Lockout Protection
- 7.3.11 Thermal Shutdown
- 7.4 D-CAP2 Control Mode
- 8 Application and Implementation
-
9 Typical Applications
- 9.1 Design Requirements
- 9.2
Detailed Design Procedure
- 9.2.1 Step One: Determine the Specifications
- 9.2.2 Step Two: Determine System Parameters
- 9.2.3 Step Three: Determine Inductor Value and Choose Inductor
- 9.2.4 Step Four: Set the Output Voltages
- 9.2.5 Step Five: Calculate SLEW Capacitance
- 9.2.6 Step Six
- 9.2.7 Step Seven: Determine the Output Capacitance
- 9.2.8 Step Eight: Select Decoupling and Peripheral Components
- 9.3 Application Examples
- 9.4 Application Curves of Design 1
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
- RUK|20
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- RUK|20
訂購信息
7.3.8 Current Sensing and Overcurrent Protection
In order to provide both cost effective solution and good accuracy, TPS51215A supports MOSFET RDS(on) sensing. For RDS(on) sensing scheme, TRIP pin should be connected to GND through the trip voltage setting resistor, RTRIP. In this scheme, TRIP terminal sources 10µA of ITRIP current (at TJ = 25°C) and the trip level is set to 1/8 of the voltage across the RTRIP. The inductor current is monitored by the voltage between the GND pin and the SW pin so that the SW pin is connected to the drain terminal of the low-side MOSFET. ITRIP has a 4700ppm/°C temperature slope to compensate the temperature dependency of the RDS(on). GND is used as the positive current sensing node so that GND should be connected to the sense resistor or the source terminal of the low-side MOSFET.
TPS51215A has cycle-by-cycle overcurrent limiting protection. The inductor current is monitored during the off-state and the controller maintains the off-state when the inductor current is larger than the overcurrent trip level. The overcurrent trip level, VOCTRIP, is determined by Equation 4.
Because the comparison is made during the off-state, VOCTRIP sets the valley level of the inductor current. The load current OCL level, IOCL, can be calculated by considering the inductor ripple current.
Overcurrent limiting using RDS(on) sensing is shown in Equation 5.
where
- IIND(ripple) is inductor ripple current
In an overcurrent condition, the current to the load exceeds the current to the output capacitor, thus the output voltage tends to fall down. Eventually, it crosses the undervoltage protection threshold and shuts down.