Current limiting circuit for push-pull output-stage LDO

Abstract

The invention provides a current limiting circuit for a push-pull output-stage LDO and belongs to the technical field of electronic circuits. The grid electrode and the source electrode of a first sampling pipe MNP1, SNS are connected with the grid electrode and the source electrode of an upper power tube MNP1, while the drain electrode of the first sampling pipe MNP1, SNS is firstly connected with a first sampling resistor RSNS1 and then connected with the drain electrode of the upper power tube MNP1. The grid electrode and the source electrode of a second sampling pipe MNP2, SNS are connected with the grid electrode and the source electrode of a lower power tube MNP2, while the drain electrode of the second sampling pipe MNP2, SNS is firstly connected with a second sampling resistor RSNS2 and then connected with the drain electrode of the lower power tube MNP2. The first sampling pipe MNP1, SNS samples the current of the upper power tube MNP1. The current flows through the first sampling resistor RSNS1 to produce a voltage drop. The second sampling pipe MNP2, SNS samples the current of the lower power tube MNP2. The current flows through the second sampling resistor RSNS2 to produce a voltage drop. An upper power tube over-current control signal CL _T and a lower power tube over-current control signal CL _B are generated and returned to the push-pull output-stage LDO circuit and then play a role together with the negative feedback loop of the LDO circuit itself. In this way, the output current is stabilized at a preset current value. The over-current damage to the power tubes is avoided. Meanwhile, no comparator is adopted, and the current detection effect and the current protection effect are simultaneously realized.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and in particular relates to a current limiting circuit suitable for a push-pull output stage LDO. Background technique [0002] The low-voltage line linear regulator LDO with push-pull output as the output stage is widely used to drive double-rate synchronous dynamic random access memory DDR memory chips. Such as figure 1 Shown is a DDR memory chip with a new power supply method, which can reduce power consumption very well. The power supply voltage VTT is driven by an LDO with a push-pull output stage to increase the output slew rate of the drive stage. During transient switching, it provides a large charging current for the gate capacitance of the power tube and improves the response speed of the power stage to the load. At the same time, the current flowing through the power tube needs to be within a safe range to ensure that the power tube will not be damaged due to excessive c...

AI Technical Summary

Problems solved by technology

Comparators are often used in traditional methods, and the circuit is more complicated, and the circuit design after the overcurrent signal is generated also increases the design cost

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