ZHCSPT6D July 2023 – June 2024 TPSM8287A06 , TPSM8287A10 , TPSM8287A12 , TPSM8287A15
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Device Options
- 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 Fixed-Frequency DCS-Control Topology
- 7.3.2 Forced-PWM and Power-Save Modes
- 7.3.3 Precise Enable
- 7.3.4 Start-Up
- 7.3.5 Switching Frequency Selection
- 7.3.6 Output Voltage Setting
- 7.3.7 Compensation (COMP)
- 7.3.8 Mode Selection / Clock Synchronization (MODE/SYNC)
- 7.3.9 Spread Spectrum Clocking (SSC)
- 7.3.10 Output Discharge
- 7.3.11 Undervoltage Lockout (UVLO)
- 7.3.12 Overvoltage Lockout (OVLO)
- 7.3.13 Overcurrent Protection
- 7.3.14 Power Good (PG)
- 7.3.15 Remote Sense
- 7.3.16 Thermal Warning and Shutdown
- 7.3.17 Stacked Operation
- 7.4 Device Functional Modes
- 7.5 Programming
- 8 Device Registers
-
9 Application and Implementation
- 9.1 Application Information
- 9.2 Typical Application
- 9.3 Typical Application Using Four TPSM8287Axx in Parallel Operation
- 9.4 Power Supply Recommendations
- 9.5 Layout
- 10Device and Documentation Support
- 11Revision History
- 12Mechanical, Packaging, and Orderable Information
7.3.2 Forced-PWM and Power-Save Modes
The device can control the inductor current in three different ways to regulate the output:
- Pulse-width modulation with continuous inductor current (PWM-CCM)
- Pulse-width modulation with discontinuous inductor current (PWM-DCM)
- Pulse-frequency modulation with discontinuous inductor current and pulse skipping (PFM-DCM)
During PWM-CCM operation, the device switches at a constant frequency and the inductor current is continuous (see Figure 7-2). PWM operation achieves the lowest output voltage ripple and the best transient performance.
Figure 7-2 Continuous Conduction Mode (PWM-CCM) Current Waveform
During PWM-DCM operation the device switches at a constant frequency and the inductor current is discontinuous (see Figure 7-3). In this mode the device controls the peak inductor current to maintain the selected switching frequency while still being able to regulate the output.
Equation 2 is used to calculate the output current threshold at which the device changes from PWM-CCM to PWM-DCM:
Figure 7-3 Discontinuous Conduction Mode (PWM-DCM) Current Waveform
During PFM-DCM operation the device keeps the peak inductor current constant (at a level corresponding to an approximately 20-ns on-time of the converter) and skips pulses to regulate the output (see Figure 7-4). The switching pulses that occur during PFM-DCM operation are synchronized to the internal clock.
Figure 7-4 Discontinuous Conduction Mode (PFM-DCM) Current WaveformEquation 3 is used to calculate the output current threshold at which the device changes from PWM-DCM to PFM-DCM:
Figure 7-5 through Figure 7-7 show how the PWM-DCM to PFM-DCM threshold typically varies with VIN and VOUT.
| MODE/SYNC = Low |
| MODE/SYNC = Low |
| MODE/SYNC = Low |
| MODE/SYNC = Low |
| MODE/SYNC = Low |
Configure the device to use either Forced-PWM Mode (FPWM) or Power-Save Mode (PSM):
- In Forced-PWM mode, the device uses PWM-CCM at all times
- In Power-Save Mode, the device uses PWM-CCM at medium and high loads, PWM-DCM at light loads, and PFM-DCM at very light loads. Transitions between the different operating modes are seamless.
Table 7-1 shows the function table of the MODE/SYNC pin and the FPWMEN bit in the CONTROL1 register, which controls the operating mode of the device.
| SSCEN Bit | FPWMEN Bit | MODE/SYNC Pin | OPERATING MODE | REMARK |
|---|---|---|---|---|
0 | 0 | Low | PSM | Do not use in a stacked configuration |
1 | 0 | Low | PSM | |
0 | 1 | X | FPWM | |
0 | X | High | FPWM | |
X | X | Sync Clock | FPWM | see Section 7.3.8 |
1 | 1 | X | FPWM | see Section 7.3.9 |
1 | X | High | FPWM |