5

6

7

8

9

10

11

12

13

1

5

9

13

17

70

80

90

100

110

120

−50

−25

0

25

50

75

100

125

150

VIN = 12 V

IOUT = 2A

2.0

2.1

2.2

−50

−25

0

25

50

75

100

125

150

3.0

4.0

5.0

6.0

−50

−25

0

25

50

75

100

125

150

RT = 100 k

Ω

VIN =12 V

IOUT = 2 A

OVERVIEW

TPS54620

TYPICAL CHARACTERISTICS (continued)

HIGH-SIDE CURRENT LIMIT THRESHOLD vs INPUT

VOLTAGE

MINIMUM CONTROLLABLE ON TIME vs TEMPERATURE

Figure 13.

Figure 14.

MINIMUM CONTROLLABLE DUTY RATIO vs JUNCTION

TEMPERATURE

BOOT-PH UVLO THRESHOLD vs TEMPERATURE

Figure 15.

Figure 16.

The device is a 17-V, 6-A, synchronous step-down (buck) converter with two integrated n-channel MOSFETs. To

improve performance during line and load transients the device implements a constant frequency, peak current

mode control which also simplifies external frequency compensation. The wide switching frequency of 200 kHz to

1600 kHz allows for efficiency and size optimization when selecting the output filter components. The switching

frequency is adjusted using a resistor to ground on the RT/CLK pin. The device also has an internal phase lock

loop (PLL) controlled by the RT/CLK pin that can be used to synchronize the switching cycle to the falling edge

of an external system clock.

The device has been designed for safe monotonic startup into pre-biased loads. The default start up is when VIN

is typically 4.0V. The EN pin has an internal pull-up current source that can be used to adjust the input voltage

under voltage lockout (UVLO) with two external resistors. In addition, the EN pin can be floating for the device to

operate with the internal pull up current. The total operating current for the device is approximately 600

µA when

not switching and under no load. When the device is disabled, the supply current is typically less than 2

µA.

The integrated MOSFETs allow for high efficiency power supply designs with continuous output currents up to 6

amperes. The MOSFETs have been sized to optimize efficiency for lower duty cycle applications.

Copyright © 2009, Texas Instruments Incorporated

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