DETAILED DESCRIPTION

-470.02

R(RSET)

V

- 0.00314

(OFF)

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(1)

TPS2412

TPS2413

SLVS728A – JANUARY 2007 – REVISED FEBRUARY 2007

The following descriptions refer to the pinout and the functional block diagram.

threshold.

Several internal comparator and amplifier circuits monitor these two pins. The inputs are protected from excess

differential voltage by a clamp diode and series resistance. If C falls below A by more than about 0.7 V, a small

current flows out of C. Protect the internal circuits with an external clamp if C can be more than 6 V lower

than A.

The internal charge pump output, which provides bias power to the comparators and voltage to drive GATE, is

referenced to A. Some charge pump current appears on A due to this topology. The A and C pins should be

Kelvin connected to the MOSFET source and drain. A and C connections should also be short and low

impedance, with special attention to the A connection. Residual noise from the charge pump can be reduced

with a bypass capacitor at A if the application permits.

BYP: BYP is the internal charge pump output, and the positive supply voltage for internal comparator circuits

and GATE driver. A capacitor must be connected from BYP to A. While the capacitor value is not critical, a

2200-pF ceramic is recommended. Traces to this part must be kept short and low impedance to provide

adequate filtering. Shorting this pin to a voltage below A damages the TPS2412/13.

GATE: Gate controls the external N channel MOSFET gate. GATE is driven positive with respect to A by a

driver operating from the voltage on BYP. A time-limited high current discharge source pulls GATE to GND when

the fast turn-off comparator is activated. The high-current discharge is followed by a sustaining pull-down. The

turn-off circuits are disabled by the thermal shutdown, leaving a resistive pull-down to keep the gate from

floating. The gate connection should be kept low impedance to maximize turn-off current.

GND: This is the input supply reference. GND should have a low impedance connection to the ground plane. It

carries several Amperes of rapid-rising discharge current when the external MOSFET is turned off, and also

carries significant charge pump currents.

threshold is slightly positive when the RSET pin is left open. Current drawn by the resistor programs the turn-off

voltage to increasing negative values. The TPS2413 must have a negative threshold programmed to avoid an

The units of the numerator are (V

× V/A). V

RSVD: Connect to ground.

lower than the controlled bus voltage.

A 0.01-

µF bypass capacitor, or 10-Ω and a 0.01-µF filter, is recommended because charge pump currents are

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