SGM3758.pdf
No.10856
● Input Voltage Range: 2.7V to 5.5V
● Integrated 3A/40V MOSFET
● Output Voltage Up to 38V (OVP)
● Output Current Up to 200mA @ 30V
● Accumulated 320ms Flash Timer Control
● 1.2MHz Switching Frequency
● PWM Dimming Control Interfaces
● PWM Frequency: 10kHz ~ 100kHz
● Strobe Interface for Image Capture Mode
● Up to 87% Efficiency for 7S2P LEDs
● Up to 92% Efficiency for 3S20P LEDs
● Dimming Stable in 1:500 Range
● 200mV Feedback Voltage in Backlight Mode
● 1000mV Feedback Voltage in Flash Mode
● Built-In Soft-Start Function
● Over-Voltage Protection
● Built-In WLED Open/Short Protection
● PFM Mode at Light Load
● Thermal Shutdown
● -40℃ to +85℃ Operating Temperature Range
● Available in Green TDFN-2×2-6L Package
With a 40V rated integrated switch FET, the SGM3758 is a boost converter that drives LEDs in series. The boost converter has a 40V, 3A internal MOSFET; thus it can drive single or parallel LED strings for small to large size panel backlighting. And it is quite suitable for smart phone image capture using display device as a flash mode light source, as it can output up to 200mA current at 30V for 320ms when the strobe signal is active.
The backlight mode default white LED current is set with the external sensor resistor, RSET, and the feedback voltage is regulated to 200mV, as shown in the typical application. During the operation, the LED current can be controlled by using a pulse width modulation (PWM) signal applied to the CTRL pin, through which the duty cycle determines the feedback reference voltage. The SGM3758 does not burst the LED current; therefore, it does not generate audible noises on the output capacitor. For maximum protection, the device features integrated open LED protection that disables the SGM3758 to prevent the output voltage from exceeding the IC absolute maximum voltage ratings during open LED conditions.
When the device is working, if the STROBE pin is pulled up, it will turn on flash mode within 100μs. And the feedback voltage is regulated to 5× of the backlight mode that determined by the PWM signal duty cycle. And it will turn to backlight mode within 100μs when the STROBE pin is pulled down or the strobe signal keeps high over the 320ms timer.
