How does guard ring prevent latch up?

How does guard ring prevent latch up?

The guardrings help intercept the diffusion of the minority carriers – and either block their diffusion by extracting them (electrons – into n+ regions, holes – into p+ regions), or by increasing the potential barrier and decreasing their lifetime, or through some other mechanism (for example, active guard rings – that …

What is a guard ring layout?

A guard ring is often copper trace that is drawn across a node in a circuit. As implied by its name, a guard ring protects the node that it is surrounding from external disturbance. The guard ring guards the high impedance input of the op-amp which is prone to current leakage.

How do you stop latch up in CMOS?

There are several ways to reduce the possibility of latchup:

1. Reduce the beta of either or both parasitic devices.
2. Increase well and substrate doping concentrations to reduce Rwell and Rsub.
3. Provide alternative (or better) collectors of the minority carriers.

Why do you need a double guard ring?

Guard rings are used to prevent injection of charge carriers from the substrate to active devices through latchup. an alternative collector or emitter for the parasitic devices to latch up to. the mutual beta factor boosting happening in the thyristor. For this we added both a P and N guard ring.

What causes latch-up?

A common cause of latch-up is a positive or negative voltage spike on an input or output pin of a digital chip that exceeds the rail voltage by more than a diode drop. Another cause is the supply voltage exceeding the absolute maximum rating, often from a transient spike in the power supply.

Why does latch-up occur?

Latch-Up is a condition where a low impedance path is created between a supply pin and ground. This condition is caused by a trigger (current injection or overvoltage), but once activated, the low impedance path remains even after the trigger is no longer present.

What are guard rings in CMOS?

Guard rings for internal and external latchup phenomena. Guard rings serve the purpose of providing electrical and spatial isolation between adjacent circuit elements preventing interaction between devices and circuits that may undergo CMOS latchup.

What is the purpose of use guard ring?

A guard ring is traditionally used to protect high impedance nodes in a circuit from surface leakage currents. The guard ring is a ring of copper driven by a low-impedance source to the same voltage as the high impedance node. This would typically be the input pin of an op-amp.

What is latch-up problem in CMOS?

Latch-Up is a condition where a low impedance path is created between a supply pin and ground. The Latch-Up condition typically requires a power cycle to eliminate the low impedance path. CMOS and BiCMOS circuits use NMOS and PMOS transistors to create the circuit functions.

What is double guarding?

In basketball, a double team (also double-team, double teaming, or double-teaming) is a defensive alignment in which two defensive players are assigned to guard a single offensive player. However, when an offensive player is overwhelming his or her defender, another defender may help out and create a double team.

What is latch-up and how do you avoid it?

Latch-up is the low resistance connection between tub and power supply rails. Also to avoid the latch, a separate tap connection is put for each transistor. But this will increase the size of the device so fabs give a minimum space to put a tap, for example, 10 μm in 130 nm technology.