Features

Input voltage range: 2.7V to 5.5V

Three -mode charging pump:

#9642; Drive six backlight LED

#9642; 32 programmable backlight current settings: 115 μA to 30mA

#9642; 2MHz switch frequency

two two Linear regulator:

#9642; 200mA output current

#9642; 200mv voltage drop

#9642; output voltage can be adjusted from 1.2V to V battery

#9642; Quick shutdown output automatic discharge

#9642; single LDO enable input

built -in heat protection

# # 8226; automatic soft start

-40 ° C to+85 ° C temperature range

tqfn44-28 packaging

Application

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Mobile devices supporting the camera

Digital camera

Multimedia mobile phone

General description ]

AAT2856

is a highly integrated charge pump with a dual -linear regulator optimized for lithium ion/polymer battery power supply system. The charging pump provides a power supply for white LED backlight. Six backlit LEDs can drive under the condition of 30 mAh. Simple interfaces are used to enable and disabled the current to one of 32 levels (high -level simple serial control #8482;) single -line interfaces. Backlight current matching is 1%, showing uniform brightness.

AAT2856 provides two high -performance low noise micro -power #8482; low -voltage differential stabilizers. Both regulators use separate enable inputs, each will provide a load current of up to 200 mA. LDO ground pins are only 80 μA, making AAT 2856 an ideal choice for battery operation applications.

AAT2856 built -in short -circuit and over -temperature protection. Soft start circuits can prevent excessive wave current when starting and mode conversion.

AAT2856 is packaged with lead-free TQFN44-28 and works within the environmental temperature range of -40 ° C to+85 ° C.

Typical application

Typical features

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Figure Figure Function description AAT2856 is the A highly integrated backlight LED drive with two LDO linear stabilizers. The charge pump LED driver driver backlit LED from 2.7V to 5.5V input voltage. The LDO regulator works within the same input voltage range, and the voltage output voltage generated is low to 1.2V.

LED drive

LED is driven by internal charging pumps. According to the battery voltage and LED forward voltage, directly drive the LED from the power supply voltage (1x or bypass mode), or increase the power supply voltage by 1.5 by 1.5 Times (1.5X mode) or 2x (2X mode). The charge pump only requires two tiny 1 μF ceramic capacitors, which provides a more compact solution than a typical inductive boost converter solution. Each separate LED is driven by a current receiver to AGND. It allows high -precision to control separate currents with high accuracy in the wide range of input voltage and LED forward voltage, while maintaining high efficiency.

The charge pump is controlled by the voltage on the LED current receiver. When any active current receiver starts to decrease, the charge pump enters the next higher mode (from 1x to 1.5X or from 1.5X to 2X mode) to maintain sufficient LED voltage to maintain a constant LED current. AAT2856 continuously monitors LED forward voltage, and uses input voltage to determine when to reduce the charge pump mode to obtain better efficiency. There is also a 500 millival mode conversion lag to prevent the mode between the charging pump from oscillation.

Backlight LED current level can be dynamically controlled via ASCWIRE single -line interface. The backlight part has multiple current flat bids, and the maximum current level is fixed at 20 mAh or 30 mAh, depending on the scale of programming selection.

If no one in the backlight or flash current receiver is not used, connect the current receiver to Output ". The current controller monitor the receiver voltage. If it is connected to the OUT