Synchronous substrate injection clamp

1. An integrated circuit comprising:

a substrate;

a first FET formed on said substrate, said first FET comprising a first terminal coupleable to a load, a second terminal and a control terminal, said second terminal being connected to said substrate;

said substrate comprising a parasitic body diode coupled between said first FET first terminal and said substrate, said body diode becoming conductive when a reverse voltage across said first FET first terminal and said substrate is at least a first diode forward voltage; and

a first voltage detector formed on said substrate, said first voltage detector having a first input coupled to said first FET first terminal, a second input coupled to said substrate, and an output coupled to said first FET control terminal, said first voltage detector being responsive to a reverse voltage level at said first FET first terminal less than said first diode forward voltage to turn said first FET on for the duration of a reverse voltage having at least said reverse voltage level, whereby said parasitic body diode is prevented from injecting current into said substrate.

2. The integrated circuit in accordance with claim 1 , wherein said first FET is a N-MOS type FET, said first terminal is a drain and said second terminal is a source.

3. The integrated circuit in accordance with claim 1 , comprising a first terminal formed on said substrate for coupling to a load, said first terminal being coupled to said first FET first terminal.

4. The integrated circuit in accordance with claim 1 , comprising control circuitry formed on said substrate, said control circuitry coupled to said first FET to control operation thereof.

5. The integrated circuit in accordance with claim 4 , wherein said control circuitry comprises a gate coupling said control circuitry and said first voltage detector output to said first FET control terminal.

6. An integrated circuit motor drive circuit for selectively coupling at least two windings of a motor to a voltage source of direct current power, said motor drive circuit comprising:

a substrate;

a first FET formed on said substrate, said first FET comprising a first terminal coupleable to a first winding of said motor, a second terminal and a control terminal, said first FET second terminal being connected to said substrate;

said substrate comprising a parasitic body diode coupled between said first FET first terminal and said substrate, said body diode becoming conductive when a reverse voltage across said first FET first terminal and said substrate is at least a diode forward voltage; and

a first voltage detector formed on said substrate, said first voltage detector having a first input coupled to said first FET first terminal, a second input coupled to said substrate, and an output coupled to said first FET control terminal, said first voltage detector being responsive to a reverse voltage level at said first FET first terminal that is less than said diode forward voltage to turn said first FET on for the duration of a reverse voltage having at least said reverse voltage level, whereby said parasitic body diode is prevented from injecting current into said substrate.

7. The integrated circuit in accordance with claim 6 , comprising:

a second FET formed on said substrate, said second FET comprising a first terminal coupleable to a second winding of said motor, a second terminal and a control terminal, said second FET second terminal being connected to said substrate;

said substrate comprising a second parasitic body diode coupled between said second FET first terminal and said substrate, said second body diode becoming conductive when a reverse voltage across said second FET first terminal and said substrate is at least said diode forward voltage; and

a second voltage detector formed on said substrate, said second voltage detector having a first input coupled to said second FET first terminal, a second input coupled to said substrate, and an output coupled to said second FET control terminal, said second voltage detector being responsive to a reverse voltage level at said second FET first terminal that is less than said first diode forward voltage to turn said second FET on for the duration of a reverse voltage having at least said reverse voltage level, whereby said parasitic body diode is prevented from injecting current into said substrate.

8. The integrated circuit in accordance with claim 7 , comprising a motor control circuit formed on said substrate, said motor control circuit selectively switching each of said first FET and said second FET on and off.

9. The integrated circuit in accordance with claim 8 , comprising:

first logic circuitry disposed between said motor control circuit and said first FET control terminal and between said first voltage detector and said first FET control terminal; and

second logic circuitry disposed between said motor control circuit and said second FET control terminal and between said second voltage detector and said second FET control terminal.

10. The integrated circuit in accordance with claim 9 , comprising:

a first connection terminal formed on said substrate, said first connection terminal coupled to said first FET first terminal;

a second connection terminal formed on said substrate, said second connection terminal coupled to said second FET first terminal; and

a third connection terminal formed on said substrate, said third connection terminal coupled to said substrate and to said first FET second terminal and said second FET second terminal.

11. The integrated circuit in accordance with claim 7 , wherein said first FET and said second FET are each N-MOS type, said first and second FET first terminals are each drain terminals, and said first and second FET second terminals are each source terminals.