US 9,921,594 B1 · Low dropout regulator with thin pass device

Abstract

Systems, methods and apparatus for efficient control and biasing of pass devices that include at least one thin pass device and a remaining of thick pass devices. When operated at extreme high and low voltages, the at least one thin pass device maintains operation in its saturation region of operation while the remaining pass devices may be driven into their triode regions of operation. The thin and thick pass devices are arranged in a cascode configuration that includes a plurality of stacked devices. Biasing of the thin and thick cascode devices can be according to a voltage division scheme which protects the devices when the voltage across the stack is high, and provides a skewed voltage division across the stacked devices that promotes a higher gate-to-source voltage of the thick pass devices for a lower RON. In one exemplary case, gate length of the at least one thin pass device may be reduced to provide a lower gate-to-source voltage of the thin pass device during operation in the saturation region. An exemplary implementation of an LDO controlling the pass devices for providing RF power to a power amplifier is described.

Claims21

Dependent claims

A circuit arrangement comprising:

a stack of at least two transistors arranged in a cascode configuration, comprising an input transistor and a first cascode transistor;
and
a biasing circuit configured to provide a first bias voltage to the first cascode transistor,
wherein:
a supply voltage to the stack is a varying supply voltage,
the first bias voltage is a function of the varying supply voltage and an output voltage at an output of the stack,
the varying supply voltage varies between a low supply voltage and a high supply voltage,
the output voltage is bound by a low output voltage and a high output voltage, and
a voltage gain of the biasing circuit is configured to change according to at least two conditions:
i) a first condition wherein the varying supply voltage is at the high supply voltage and the output voltage is at the low output voltage, and
ii) a second condition wherein the varying supply voltage is at the low supply voltage and the output voltage is at the high output voltage,
wherein the voltage gain of the biasing circuit during operation according to the first condition is higher than the voltage gain of the biasing circuit during operation according to the second condition, the voltage gain being defined as a ratio of the first bias voltage and the varying supply voltage.

9 more elements

Dependencies are inferred from the claim text.

Low dropout regulator with thin pass device

Life of this patent

Low dropout regulator with thin pass device

Life of this patent

Abstract

Claims21