ZHCSNK8 March 2021 TPS62810M , TPS62811M , TPS62812M , TPS62813M
PRODUCTION DATA
- 1 特性
- 2 應用
- 3 說明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Parameter Measurement Information
- 9 Detailed Description
- 10Application and Implementation
- 11Power Supply Recommendations
- 12Layout
- 13Device and Documentation Support
- 14Mechanical, Packaging, and Orderable Information
10.3.1 Voltage Tracking
The TPS6281xM device follows the voltage applied to the SS/TR pin. A voltage ramp on SS/TR to 0.6 V ramps the output voltage according to the 0.6-V feedback voltage.
Tracking the 3.3 V of device 1, such that both rails reach their target voltage at the same time, requires a resistor divider on SS/TR of device 2 equal to the output voltage divider of device 1. The output current of 2.5 μA on the SS/TR pin causes an offset voltage on the resistor divider formed by R5 and R6. The equivalent resistance of R5 // R6, so it must be kept below 15 kΩ. The current from SS/TR causes a slightly higher voltage across R6 than 0.6 V, which is desired because device 2 switches to its internal reference as soon as the voltage at SS/TR is higher than 0.6 V.
In case both devices need to run in forced PWM mode, it is recommended to tie the MODE pin of device 2 to the output voltage or the power good signal of device 1, the main device. The TPS6281xM device has a duty cycle limitation defined by the minimum on time. For tracking down to low output voltages, device 2 cannot follow once the minimum duty cycle is reached. Enabling PFM mode while tracking is in progress allows the user to ramp down the output voltage close to 0 V.
Figure 10-58 Scope Plot for Output Voltage Tracking