ZHCS826C January 2012 – November 2023 TPS40170-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 4 Pin Configuration and Functions
- 5 Specifications
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3
Feature Description
- 6.3.1 LDO Linear Regulators and Enable
- 6.3.2 Input Undervoltage Lockout (UVLO)
- 6.3.3 Equations for Programming the Input UVLO
- 6.3.4 Overcurrent Protection and Short-Circuit Protection (OCP and SCP)
- 6.3.5 Oscillator and Voltage Feed-Forward
- 6.3.6 Feed-Forward Oscillator Timing Diagram
- 6.3.7 Soft-Start and Fault-Logic
- 6.3.8 Overtemperature Fault
- 6.3.9 Tracking
- 6.3.10 Adaptive Drivers
- 6.3.11 Start-Up Into Pre-Biased Output
- 6.3.12 31
- 6.3.13 Power Good (PGOOD)
- 6.3.14 PGND and AGND
- 6.3.15 Bootstrap Capacitor
- 6.3.16 Bypass and Filtering
- 6.4 Device Functional Modes
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Application
- 7.2.1 Design Requirements
- 7.2.2
Detailed Design Procedure
- 7.2.2.1 Select A Switching Frequency
- 7.2.2.2 Inductor Selection (L1)
- 7.2.2.3 Output Capacitor Selection (C9)
- 7.2.2.4 Peak Current Rating of Inductor
- 7.2.2.5 Input Capacitor Selection (C1, C6)
- 7.2.2.6 MOSFET Switch Selection (Q1, Q2)
- 7.2.2.7 Timing Resistor (R7)
- 7.2.2.8 UVLO Programming Resistors (R2, R6)
- 7.2.2.9 Bootstrap Capacitor (C7)
- 7.2.2.10 VIN Bypass Capacitor (C18)
- 7.2.2.11 VBP Bypass Capacitor (C19)
- 7.2.2.12 SS Timing Capacitor (C15)
- 7.2.2.13 ILIM Resistor (R19, C17)
- 7.2.2.14 SCP Multiplier Selection (R5)
- 7.2.2.15 Feedback Divider (R10, R11)
- 7.2.2.16 Compensation: (R4, R13, C13, C14, C21)
- 7.2.3 Application Curves
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
7.2.2.13 ILIM Resistor (R19, C17)
The TPS40170-Q1 controller uses the negative drop across the low-side FET at the end of the OFF time to measure the inductor current. Allowing for 30% over the minimum current limit for transient recovery and a 20% rise in RDS(on)Q2 for self-heating of the MOSFET, the voltage drop across the low-side FET at the current limit is given by Equation 39.
Equation 39. 
The internal current-limit temperature coefficient helps compensate for the MOSFET RDS(on) temperature coefficient, so the current-limit programming resistor is selected by Equation 40.
Equation 40. 
A 1000-pF capacitor is placed in parallel to improve noise immunity of the current-limit set-point.