SGM41526

The SGM41526 and SGM41527 are stand-alone Li-Ion and Li-polymer battery chargers. The PWM switches are integrated inside and they can automatically select the power path. They also include gate drivers for external power path selector MOSFETs. The synchronous PWM controller runs at a fixed frequency (1.6MHz) and is capable of providing accurate regulation of charge voltage, charge current and input current. They are capable of providing continuous battery pack temperature monitoring in which the charge is only allowed when the temperature is within the desired range. The SGM41526 can charge 2-, 3- or 4-cell (selected by CELL pin); while the SGM41527 has an adjustable charge voltage for up to 4 cells. In the SGM41527, the FB pin is used for charge voltage regulation (feedback) using an internal 2.1V reference and comparator.

Typically, a full battery charging cycle has three consequent phases: pre-conditioning, constant current and constant voltage. The charge current is small during the pre-conditioning phase in which battery is heavily depleted. When the battery voltage exceeds a threshold voltage, the charge current increases to its maximum (fast charge current) until the battery voltage reaches its regulation level. Then the voltage is regulated and charge current drops. The starting phase is determined by the initial battery voltage. In constant voltage condition, the charge current drops automatically. When it decreases below 10% of the fast charge value, charging is terminated. A programmable safety charge timer is provided to prevent prolonged charging if it is not naturally terminated for any reason. When the battery voltage falls below recharge threshold, charge cycle is automatically started (or restarted).

If the input voltage falls below the battery voltage, the device enters sleep mode. In sleep mode, the quiescent current is very low.

The SGM41526 and SGM41527 use dynamic power management (DPM) to prevent overload of the input source (AC adaptor). With DPM, the output charge current is reduced if the input power limit is reached. The input current is sensed and controlled by a precision current-sense amplifier to limit the input power.

Gate driver outputs are provided for power path selection that can be achieved by three external switches. Two N-type back-to-back MOSFETs (Q1, Q2) are used as input pair (adapter power in and reverse blocking control) along with a P-type (Q3) that is used to control the battery connection to the system bus. The system is powered from adapter by Q1 and Q2 on if a qualified adapter is present. Otherwise, the system is connected to the battery by Q3. And with power path control, the battery cannot feed back to the input.

The SGM41526 and SGM41527 can charge the battery from a DC source with a voltage up to 22V. This range covers common adapter voltages and the car battery voltage. The qualified adapter range is adjustable by OVPSET pin. If the input voltage is out of the range, Q1 and Q2 will not be turned on.

For 1-cell applications (only applicable to SGM41527), when the battery is not removable, the design can be simplified by direct connection of the battery to the system. Therefore, when the input source is overloaded, the battery can help power the system automatically.

The SGM41526 and SGM41527 are available in a Green TQFN-5.5×3.5-24L package. It can operate over an ambient temperature range of -40℃ to +85℃.