LT8210 datasheet(32/59 Pages) AD

32 / 59 page

Data Sheet

LT8210-1

analog.com

Rev. A

32 of 59

high (e.g., MODE1, MODE2, and SYNC/SPRD) and as the pull-up supply for the PWGD pin. The VDD regulator has a 9mA

current limit. For powering external loads other than those described from the VDD rail, contact the factory for

support.

Figure 55. GATEVCC Current Limit vs. VINP, EXTVCC

Reverse Input Protection

The LT8210-1 includes optional reverse input protection down to –40V. To implement a power N-channel MOSFET,

it should be placed with its source connected to VIN, its drain connected to VINP, and its gate connected to the DG pin.

When the voltage at the VIN drops below –1.2V (typical), the DG pin is clamped to the VIN pin through an internal 30Ω

(typical) switch. With its gate and source shorted, the external MOSFET is forced into cutoff, disconnecting VINP and

downstream circuitry from the input and preventing damage. The VIN, DG, and EN/UVLO pins are all able to withstand

voltages down to –40V without damage or excessive current flow. If polarized capacitors are used for input filtering,

they should be placed on the VINP side of the DG MOSFET. During normal operation, the DG – VIN voltage is charged to

approximately 8.5V via the internal charge pump in order to fully enhance the MOSFET. Switching will be disabled if

the DG – VIN voltage drops below 2.1V (typical) and re-enabled when it exceeds 2.8V (typical). The DG undervoltage

lockout is intended to prevent excessive power dissipation in the DG MOSFET when it is not enhanced and current

conducts through its body diode. The internal charge pump is able to source up to 180μA from the DG pin for fast

charging and minimal delay at start-up. If reverse input protection is not needed, VINP should be connected to VIN

directly or through a small RC filter (e.g., 1Ω, 1μF), and a 1nF, 25V ceramic capacitor should be placed between the

DG and VIN pins.

Figure 56. Implementing Reverse Input Protection

FROM VINP

FROM EXTVCC

VOLTAGE (V)

100

120

POWER INPUT

–40V TO +100V

TO DRAIN OF

SWITCH A

VIN

VINP

LT8210-1

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