LM3560 datasheet(14/48 Pages) TI1

14 / 48 page

LM3560

SNOSB43B – SEPTEMBER 2011 – REVISED AUGUST 2013

www.ti.com

OVER-VOLTAGE PROTECTION

The output voltage is limited to typically 5V (5.075V max). In situations such as the current source open, the

LM3560 will raise the output voltage to try to keep the LED current at its target value. When VOUT reaches 5V the

over-voltage comparator will trip and turn off both the internal NFET and PFET. When VOUT falls below 4.8V

(typical), the LM3560 will begin switching again.

CURRENT LIMIT

The LM3560 features 4 selectable current limits of 1.6A, 2.3A, 3.0A, and 3.6A. These are programmable through

the I2C-compatible interface via bits [6:5] of the Flash Duration Register. When the current limit is reached, the

LM3560 stops switching for the remainder of the switching cycle.

Since the current limit is sensed in the NMOS switch there is no mechanism to limit the current when the device

operates in Pass Mode. In situations where there could potentially be large load currents at OUT, and the

LM3560 is operating in Pass mode, the load current must be limited to 3A. In Boost mode or Pass mode if VOUT

falls below approximately 2.3V, the part stops switching and the PFET operates as a current source, limiting the

current to typically 350 mA. This prevents damage to the LM3560 and excessive current draw from the battery

during output short-circuit conditions.

THERMAL SHUTDOWN

The LM3560 features a thermal shutdown threshold of typically +150°C. When the devices die temperature

reaches +150°C the active current sources (LED1 and/or LED2) will shut down, and the TSD flag in the Flags

Flags register is read back either current source can be re-enabled into Privacy, Torch, or Flash Mode. The

thermal shutdown (TSD) circuitry has an internal 250 µs de-glitch timer which helps prevent unwanted noise from

falsely triggering a TSD event. However, when the LM3560 is in boost mode at higher flash currents, the de-

glitch timer can get reset by the high currents in the LM3560's GND. As a result the thermal shutdown's internal

de-glitch timer can be reset before the TSD event can get latched in. This prevents a TSD event from being

triggered until the LM3560's flash pulse reaches the end of the flash duration, when the noisy currents have

dropped to a lower level. However, once the noise is lower, and a TSD event is triggered, the next flash pulse is

not allowed until the flags register is read back. In pass mode the boost switcher is off and the lower noise

environment allows the devices TSD circuitry to shut down immediately when the die temperature reaches

+150°C.

FLASH MODE

In Flash mode the LED current sources (LED1 and LED2) each provide 16 different current levels from typically

62.5 mA (total) to 2A (total) in steps of 62.5 mA. The Flash currents are adjusted via the Flash Brightness

hardware flash input (STROBE) via bit [2] of Configuration Register 1, and then pulling the STROBE pin high

(high polarity). Once the Flash sequence is activated the active current sources (LED1 and/or LED2) will ramp up

to their programmed Flash current level by stepping through all Torch and Flash levels (32 µs/step) until the

programmed current is reached.

Bit [5] of the Enable Register (STROBE Level/Edge bit) determines how the Flash pulse terminates after

STROBE goes high. With the Level/Edge bit = 1, the Flash current will only terminate when it reaches the end of

the Flash Timeout period. With the Level/Edge bit = 0, Flash mode can be terminated by pulling STROBE low,

programming bits [1:0] of the Enable Register with (0,0), or by allowing the Flash Timeout period to elapse. If the

Level/Edge bit = 0 and STROBE is toggled before the end of the Flash Timeout period, the Timeout period will

reset. Figure 25 and Figure 26 detail the Flash pulse termination for the different Level/Edge bit settings.

Submit Documentation Feedback

Product Folder Links: LM3560

LM3560 Datasheet(PDF) 14 Page - Texas Instruments

LM3560 Datasheet(HTML) 14 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

Datasheet Download

Link URL