LM76005 datasheet(16/51 Pages) TI2

16 / 51 page

Enable

Internal SS Ramp

Ext Tracking Signal to SS pin

VOUT

Figure 7-5. Tracking with Longer Start-up Time than the Internal Ramp

Enable

Internal SS Ramp

Ext Tracking Signal to SS pin

VOUT

Figure 7-6. Tracking with Shorter Start-up Time than the Internal Ramp

The LM76005 is capable of start-up into pre-biased output conditions. During start-up, the device sets the

minimum inductor current to zero to avoid discharging a pre-biased load.

7.3.7 Adjustable Switching Frequency (RT) and Frequency Synchronization

The switching frequency of the LM76005 can be programmed by the impedance RT from the RT pin to ground.

The frequency is inversely proportional to the RT resistance. The RT pin can be left floating, and the LM76005

operates at 400-kHz default switching frequency. The RT pin is not designed to be shorted to ground.

For an desired frequency, RT can be found by:

38400

R (k ) =

Frequency(kHz)

14.33

(6)

Table 7-1. Switching Frequency vs RT

SWITCHING FREQUENCY (kHz)

RT RESISTANCE (kΩ)

200

206.82

300

134.42

400

99.57

500

79.07

The LM76005 switching action can also be synchronized to an external clock from 200 kHz to 500 kHz. TI

recommends connecting an external clock to the SYNC pin with an appropriate termination resistor. Ground the

SYNC pin if not used.

SYNC

TERM

EXT CLOCK

Figure 7-7. Frequency Synchronization

The recommendations for the external clock include high level no lower than 2 V, low level no higher than 0.4 V,

duty cycle between 10% and 90%, and both positive and negative pulse width no shorter than 80 ns. When the

external clock fails at logic high or low, the LM76005 switches at the frequency programmed by the RT resistor

after a time-out period. TI recommends connecting a resistor RT to the RT pin so that the internal oscillator

frequency is the same as the target clock frequency when the LM76005 is synchronized to an external clock.

LM76005

SNVSBK5A – FEBRUARY 2020 – REVISED JULY 2020

www.ti.com

Submit Document Feedback

Product Folder Links: LM76005

LM76005 Datasheet(PDF) 16 Page - Texas Instruments

LM76005 Datasheet(HTML) 16 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

Datasheet Download

Link URL