CMOS Charge Pump Latch-Up Immunity via Bulk Voltage Control
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Solution Overview
Problem
CMOS charge pumps face reliability issues due to latch-up phenomena caused by leakage current flowing into the bulk of PMOS transistors, which degrades output efficiency and reliability, especially when transferring high voltages.
Innovation Solution
A CMOS charge pump design that includes a bulk voltage adjustor to disconnect the boost nodes from the bulk node when a blocking control signal is activated, and an auxiliary pump to precharge the bulk node, maintaining the bulk voltage at a predetermined level or higher, thereby preventing latch-up by ensuring the bulk voltage is always higher than the source or drain voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PMOS transistors are used as transfer switches to transfer high voltage without threshold-voltage loss, then output efficiency is improved, but latch-up phenomenon occurs due to leakage current flowing into the bulk
Solution Approach 1:
A bulk voltage adjustor is introduced as an intermediary component between the boost nodes and the bulk node. This adjustor includes control transistors that mediate the connection, allowing the bulk voltage to be independently controlled and adjusted to a level higher than the source/drain voltage, thereby preventing latch-up while maintaining the benefits of PMOS transfer switches
Solution Approach 2:
The bulk voltage parameter is actively changed and controlled to be higher than the source or drain voltage of the PMOS transistors. By adjusting the bulk voltage level through the bulk voltage adjustor, the electrical conditions are modified to prevent latch-up phenomenon while preserving the threshold-voltage-free transfer capability
2Power
If the bulk of PMOS transistor is directly connected to the output node to vary bulk voltage with output voltage, then high voltage transfer is improved, but leakage current causes latch-up phenomenon
Solution Approach 1:
The direct connection between the output node and bulk node is segmented into a controlled path through the bulk voltage adjustor. This segmentation allows independent control of the bulk voltage adjustment process, separating the high voltage transfer function from the bulk voltage control function to eliminate latch-up caused by direct connection
Solution Approach 2:
The bulk voltage adjustor acts as an intermediary between the output node and the bulk node, providing controlled voltage adjustment rather than direct connection. This intermediary structure prevents leakage current from directly affecting the bulk while still enabling the bulk voltage to follow the output voltage trajectory at a safe level
Data Source
AI summary
A CMOS charge pump with improved latch-up immunity is provided. The CMOS charge pump includes a blocking transistor that disconnects first and second boost nodes from a bulk node in response to a blocking control signal, such that a bulk voltage can be maintained at a predetermined level or higher. The CMOS charge pump in a power-up period first precharges the bulk voltage before the main pump performs a boosting operation and prevents a latch-up phenomenon.