TPS54560DDAR

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1. Description

The TPS54560DDAR is a 60 V, 5 A, step down regulator with an integrated high side MOSFET. The device survives load dump pulses up to 65V per ISO 7637. Current mode control provides simple external compensation and flexible component selection. A low ripple pulse skip mode reduces the no load supply current to 146 μA. Shutdown supply current is reduced to 2 μA when the enable pin is pulled low. Undervoltage lockout is internally set at 4.3 V but can be increased using the enable pin. The output voltage start up ramp is internally controlled to provide a controlled start up and eliminate overshoot. A wide switching frequency range allows either efficiency or external component size to be optimized. Output current is limited cycle-by-cycle. Frequency foldback and thermal shutdown protects internal and external components during an overload condition. The TPS54560 is available in an 8-terminal thermally enhanced HSOP PowerPAD™ package.

2. Features

    1. High Efficiency at Light Loads with Pulse Skipping Eco-mode™

    2. 92-mΩ High-Side MOSFET

    3. 146 μA Operating Quiescent Current and 2 μA Shutdown Current

    4. 100 kHz to 2.5 MHz Fixed Switching Frequency

    5. Synchronizes to External Clock

    6. Low Dropout at Light Loads with Integrated BOOT Recharge FET

    7. Adjustable UVLO Voltage and Hysteresis

    8. 0.8 V 1% Internal Voltage Reference

    9. 8-Terminal HSOP with PowerPAD™ Package

  10. –40°C to 150°C TJ Operating Range

  11. Create a Custom Design using the TPS54560 with the WEBENCH® Power Designer

3. Applications

    1. Industrial Automation and Motor Control

    2. Vehicle Accessories: GPS, Entertainment

    3. USB Dedicated Charging Ports and Battery Chargers

    4. 12 V, 24 V and 48 V Industrial, Automotive and Communications 

4. Pin Configuration 

5. Pin Functions

6. Feature Description

1. Fixed Frequency PWM Control

The TPS54560 uses fixed frequency, peak current mode control with adjustable switching frequency. The output voltage is compared through external resistors connected to the FB terminal to an internal voltage reference by an error amplifier. An internal oscillator initiates the turn on of the high side power switch. The error amplifier output at the COMP terminal controls the high side power switch current. When the high side MOSFET switch current reaches the threshold level set by the COMP voltage, the power switch is turned off. The COMP terminal voltage will increase and decrease as the output current increases and decreases. The device implements current limiting by clamping the COMP terminal voltage to a maximum level. The pulse skipping Eco-mode is implemented with a minimum voltage clamp on the COMP terminal.

2. Slope Compensation Output Current

The TPS54560 adds a compensating ramp to the MOSFET switch current sense signal. This slope compensation prevents sub-harmonic oscillations at duty cycles greater than 50%. The peak current limit of the high side switch is not affected by the slope compensation and remains constant over the full duty cycle range.

3. Pulse Skip Eco-mode

The TPS54560 operates in a pulse skipping Eco-mode at light load currents to improve efficiency by reducing switching and gate drive losses. If the output voltage is within regulation and the peak switch current at the end of any switching cycle is below the pulse skipping current threshold, the device enters Eco-mode. The pulse skipping current threshold is the peak switch current level corresponding to a nominal COMP voltage of 600 mV. When in Eco-mode, the COMP terminal voltage is clamped at 600 mV and the high side MOSFET is inhibited. Since the device is not switching, the output voltage begins to decay. The voltage control loop responds to the falling output voltage by increasing the COMP terminal voltage. The high side MOSFET is enabled and switching resumes when the error amplifier lifts COMP above the pulse skipping threshold. The output voltage recovers to the regulated value, and COMP eventually falls below the Eco-mode pulse skipping threshold at which time the device again enters Eco-mode. The internal PLL remains operational when in Eco-mode. When operating at light load currents in Eco-mode, the switching transitions occur synchronously with the external clock signal. During Eco-mode operation, the TPS54560 senses and controls peak switch current, not the average load current. Therefore the load current at which the device enters Eco mode is dependent on the output inductor value. The circuit in Figure 33 enters Eco-mode at about 25.3 mA output current. As the load current approaches zero, the device enters a pulse skip mode during which it draws only 146 μA input quiescent current.

4. Low Dropout Operation and Bootstrap Voltage (BOOT)

The TPS54560 provides an integrated bootstrap voltage regulator. A small capacitor between the BOOT and SW terminals provides the gate drive voltage for the high side MOSFET. The BOOT capacitor is refreshed when the high side MOSFET is off and the external low side diode conducts. The recommended value of the BOOT capacitor is 0.1 μF. A ceramic capacitor with an X7R or X5R grade dielectric with a voltage rating of 10 V or higher is recommended for stable performance over temperature and voltage. When operating with a low voltage difference from input to output, the high side MOSFET of the TPS54560 will operate at 100% duty cycle as long as the BOOT to SW terminal voltage is greater than 2.1 V. When the voltage from BOOT to SW drops below 2.1V, the high side MOSFET is turned off and an integrated low side MOSFET pulls SW low to recharge the BOOT capacitor. To reduce the losses of the small low side MOSFET at high output voltages, it is disabled at 24 V output and re enabled when the output reaches 21.5 V. Since the gate drive current sourced from the BOOT capacitor is small, the high side MOSFET can remain on for many switching cycles before the MOSFET is turned off to refresh the capacitor. Thus the effective duty cycle of the switching regulator can be high, approaching 100%. The effective duty cycle of the converter during dropout is mainly influenced by the voltage drops across the power MOSFET, the inductor resistance, the low side diode voltage and the printed circuit board resistance.