ZHCSL68C April 2017 – December 2020 TPS7A84A
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Pin Configuration and Functions
-
6 Specifications
- 6.1 Absolute Maximum Ratings
- 6.2 ESD Ratings
- 6.3 Recommended Operating Conditions
- 6.4 Thermal Information
- 6.5 Electrical Characteristics: General
- 6.6 Electrical Characteristics: TPS7A8400A
- 6.7 Electrical Characteristics: TPS7A8401A
- 6.8 Typical Characteristics: TPS7A8400A
- 6.9 Typical Characteristics: TPS7A8401A
- 7 Detailed Description
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8 Application and Implementation
- 8.1
Application Information
- 8.1.1
External Component Selection
- 8.1.1.1 Adjustable Operation
- 8.1.1.2 ANY-OUT Programmable Output Voltage
- 8.1.1.3 ANY-OUT Operation
- 8.1.1.4 Increasing ANY-OUT Resolution for LILO Conditions
- 8.1.1.5 Current Sharing
- 8.1.1.6 Recommended Capacitor Types
- 8.1.1.7 Input and Output Capacitor Requirements (CIN and COUT)
- 8.1.1.8 Feed-Forward Capacitor (CFF)
- 8.1.1.9 Noise-Reduction and Soft-Start Capacitor (CNR/SS)
- 8.1.2 Start-Up
- 8.1.3 AC and Transient Performance
- 8.1.4 DC Performance
- 8.1.5 Sequencing Requirements
- 8.1.6 Negatively Biased Output
- 8.1.7 Reverse Current Protection
- 8.1.8 Power Dissipation (PD)
- 8.1.1
External Component Selection
- 8.2 Typical Applications
- 8.1
Application Information
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
8.1.3.1 Power-Supply Rejection Ratio (PSRR)
PSRR is a measure of how well the LDO control loop rejects signals from VIN to VOUT across the frequency spectrum (usually 10 Hz to 10 MHz). Equation 9 gives the PSRR calculation as a function of frequency for the input signal [VIN(f)] and output signal [VOUT(f)].
Even though PSRR is a loss in signal amplitude, PSRR is shown as positive values in decibels (dB) for convenience.
A simplified diagram of PSRR versus frequency is shown in Figure 8-6.
Figure 8-6 Power-Supply Rejection Ratio DiagramAn LDO is often employed not only as a dc-dc regulator, but also to provide exceptionally clean power-supply voltages that exhibit ultra-low noise and ripple to sensitive system components. This usage is especially true for the TPS7A84A.
The TPS7A84A features an innovative circuit to boost the PSRR from 200 kHz to 1 MHz; see Figure 6-1. To achieve the maximum benefit of this PSRR boost circuit, TI recommends using a capacitor with a minimum impedance in the 100-kHz to 1-MHz band.