TPS2811-Q1

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SLVSAE0 – JUNE 2010

APPLICATION INFORMATION

The TPS2811 circuits each contain one regulator and two MOSFET drivers. The regulator can be used to limit

VCC to between 10 V and 13 V for a range of input voltages from 14 V to 40 V, while providing up to 20 mA of dc

drive. The TPS2811 has inverting drivers. These MOSFET drivers are capable of supplying up to 2.1 A or sinking

up to 1.9 A (see Figures 15 and 16) of instantaneous current to n-channel or p-channel MOSFETs. The

TPS2811 MOSFET drivers have very fast switching times combined with very short propagation delays. These

features enhance the operation of today’s high-frequency circuits.

The CMOS input circuit has a positive threshold of approximately 2/3 of VCC, with a negative threshold of 1/3 of

VCC, and a very high input impedance in the range of 109Ω. Noise immunity is also very high because of the

Schmitt-trigger switching. In addition, the design is such that the normal shoot-through current in CMOS (when

the input is biased halfway between VCC and ground) is limited to less than 6 mA. The limited shoot-through is

evident in the graphs in Figures 17 and 18. The input stage shown in the functional block diagram better

illustrates the way the front end works. The circuitry of the device is such that regardless of the rise and/or fall

time of the input signal, the output signal will always have a fast transition speed; this basically isolates the

waveforms at the input from the output. Therefore, the specified switching times are not affected by the slopes of

the input waveforms.

The basic driver portion of the circuits operate over a supply voltage range of 4 V to 14 V with a maximum bias

current of 5 µA. Each driver consists of a CMOS input and a buffered output with a 2-A instantaneous drive

capability. They have propagation delays of less than 30 ns and rise and fall times of less than 20 ns each.

Placing a 0.1-µF ceramic capacitor between VCC and ground is recommended; this will supply the instantaneous

current needed by the fast switching and high current surges of the driver when it is driving a MOSFET.

The output circuit is also shown in the functional block diagram. This driver uses a unique combination of a

bipolar transistor in parallel with a MOSFET for the ability to swing from VCC to ground while providing 2 A of

instantaneous driver current. This unique parallel combination of bipolar and MOSFET output transistors provides

the drive required at VCC and ground to guarantee turn-off of even low-threshold MOSFETs. Typical bipolar-only

output devices don’t easily approach VCC or ground.

The regulator included in the TPS2811 has an input voltage range of 14 V to 40 V. It produces an output voltage

of 10 V to 13 V and is capable of supplying from 0 to 20 mA of output current. In grounded source applications,

this extends the overall circuit operation to 40 V by clamping the driver supply voltage (VCC) to a safe level for

both the driver and the MOSFET gate. The bias current for full operation is a maximum of 150 µA. A 0.1-µF

capacitor connected between the regulator output and ground is required to ensure stability. For transient

response, an additional 4.7-µF electrolytic capacitor on the output and a 0.1-µF ceramic capacitor on the input

will optimize the performance of this circuit. When the regulator is not in use, it can be left open at both the input

and the output, or the input can be shorted to the output and tied to either the VCC or the ground pin of the chip.

Copyright © 2010, Texas Instruments Incorporated

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Product Folder Link(s): TPS2811-Q1