LM36010 Datasheet, PDF (16/37 Pages) Texas Instruments – Synchronous-Boost, Single-LED Flash Driver With 1.5-A High-Side Current Source

LM36010
SNVSAN4A – APRIL 2017 – REVISED JULY 2017
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7.4 Device Functioning Modes
7.4.1 Start-Up (Enabling The Device)
At turnon the LED current source steps through each FLASH or TORCH level until the target LED current is
reached. This gives the device a controlled turnon and limits inrush current from the V_IN supply. The target LED
flash and the target LED torch currents are set by the LED Flash Brightness Register (0x03 bits [6:0]) and LED
Torch Brightness Register (0x04 bits [6:0]) respectively.
7.4.2 Pass Mode
The LM36010 starts up in pass mode and stays there until boost mode is needed to maintain regulation. If the
voltage difference between V_OUT and V_LED falls below V_HR, the device switches to boost mode. In pass mode, the
boost converter does not switch, the synchronous PFET turns fully on bringing V_OUT up to V_IN – I_LED × R_PMOS,
and the inductor current is not limited by the peak current limit.
7.4.3 Input Voltage Flash Monitor (IVFM)
The LM36010 has the ability to adjust the flash current based upon the voltage level present at the IN pin
utilizing the input voltage flash monitor (IVFM). The adjustable threshold IVFM-D ranges from 2.9 V to 3.6 V in
100-mV steps and is set by Configuration Register (0x02) bits [7:5]. Additionally, the IVFM-D threshold sets the
input voltage boundary that forces the LM36010 to stop ramping the flash current during start-up.
IVFM ENABLE
LEVEL STROBE
VIN PROFILE for Stop and Hold Mode
IVFM-D
O/P Current Profile in
Stop and Hold Mode
Set Target Flash Current
Dotted line shows O/P Current Profile with
IVFM Disabled
SET RAMP FROM
THE RAMP
REGISTER USED
Figure 32. IVFM Mode
7.4.4 Fault/Protections
Upon a fault condition, the LM36010 sets the appropriate flag(s) in the Flags Register (0x05) and switches into
stand-by mode obtained by clearing the mode M1, M0 (bits [1:0]) of the Enable Register (0x01). The LM36010
remains in standby until an I²C read of the Flags Register. I²C read of the Flags Register clears the flags and the
fault status can be re-checked. If the fault(s) is still present, the LM36010 re-sets the appropriate flag bits and
enters stand-by again.
7.4.4.1 Overvoltage Protection (OVP)
The output voltage is limited to typically 5 V (see V_OVP specification in the Electrical Characteristics). In situations
such as an open LED, the LM36010 raises the output voltage in order to keep the LED current at its target value.
When V_OUT reaches 5 V (typical), the overvoltage comparator trips and turns off the internal NFET. When OVP
condition is present for three consecutive OVP events, LM36010 enters stand-by mode and OVP flag (bit [0]) of
Flags Register (0x01) is set. Checking for three consecutive events prevents forcing the device to shut down due
to momentary OVP condition. When V_OUT falls below the V_OVP off threshold, the LM36010 switches again.
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