Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- ABSOLUTE MAXIMUM RATINGS
- THERMAL INFORMATION
- ELECTRICAL CHARACTERISTICS
- DEVICE INFORMATION
- TYPICAL CHARACTERISTICS
- OVERVIEW
- DETAILED DESCRIPTION
- Fixed Frequency PWM Control
- Slope Compensation Output Current
- Pulse Skip Eco-Mode
- Low Dropout Operation and Bootstrap Voltage (BOOT)
- Error Amplifier
- Voltage Reference
- Adjusting the Output Voltage
- Enable and Adjusting Undervoltage Lockout
- Slow Start/Tracking Pin (SS/TR)
- Overload Recovery Circuit
- Sequencing
- Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
- Overcurrent Protection and Frequency Shift
- Selecting the Switching Frequency
- How to Interface to RT/CLK Pin
- Power Good (PWRGD Pin)
- Overvoltage Transient Protection
- Thermal Shutdown
- Small Signal Model for Loop Response
- Simple Small Signal Model for Peak Current Mode Control
- Small Signal Model for Frequency Compensation
- APPLICATION INFORMATION
- Design Guide — Step-By-Step Design Procedure
- Selecting the Switching Frequency
- Output Inductor Selection (LO)
- Output Capacitor
- Catch Diode
- Input Capacitor
- Slow Start Capacitor
- Bootstrap Capacitor Selection
- Under Voltage Lock Out Set Point
- Output Voltage and Feedback Resistors Selection
- Compensation
- Discontinuous Mode and Eco Mode Boundary
- APPLICATION CURVES
- Power Dissipation Estimate
- Layout
- Revision History
VOUT
(ac)
I
L
PH
TPS54060
www.ti.com
SLVS919A –JANUARY 2009–REVISED JULY 2010
DETAILED DESCRIPTION (continued)
Figure 25. Pulse Skip Mode Operation
Low Dropout Operation and Bootstrap Voltage (BOOT)
The TPS54060 has an integrated boot regulator, and requires a small ceramic capacitor between the BOOT and
PH pins to provide the gate drive voltage for the high side MOSFET. The BOOT capacitor is refreshed when the
high side MOSFET is off and the low side diode conducts. The value of this ceramic capacitor should be 0.1mF.
A ceramic capacitor with an X7R or X5R grade dielectric with a voltage rating of 10V or higher is recommended
because of the stable characteristics overtemperature and voltage.
To improve drop out, the TPS54060 is designed to operate at 100% duty cycle as long as the BOOT to PH pin
voltage is greater than 2.1V. When the voltage from BOOT to PH drops below 2.1V, the high side MOSFET is
turned off using an UVLO circuit which allows the low side diode to conduct and refresh the charge on the BOOT
capacitor. Since the supply current sourced from the BOOT capacitor is low, the high side MOSFET can remain
on for more switching cycles than are required to refresh the capacitor, thus the effective duty cycle of the
switching regulator is high.
The effective duty cycle during dropout of the regulator is mainly influenced by the voltage drops across the
power MOSFET, inductor resistance, low side diode and printed circuit board resistance. During operating
conditions in which the input voltage drops and the regulator is operating in continuous conduction mode, the
high side MOSFET can remain on for 100% of the duty cycle to maintain output regulation, until the BOOT to PH
voltage falls below 2.1V.
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