ADP2126/ADP2127

Rev. A | Page 13 of 20

Undervoltage Lockout (UVLO)

PROTECTION FEATURES

If the input voltage is below the UVLO threshold, the ADP2126/

ADP2127 automatically turn off the power switches and place the

parts in a low power consumption mode. This prevents potentially

erratic operation at low input voltages. The UVLO levels have

approximately 100 mV of hysteresis to ensure glitch-free startup.

Overcurrent Protection

To ensure that excessively high currents do not damage the

MOSFET switches, the ADP2126/ADP2127 incorporate cycle-by-

cycle overcurrent protection. This function is accomplished by

monitoring the instantaneous peak current on the power PMOS

switch. If this current exceeds the PMOS switch current limit

(1 A typical), then the PMOS is immediately turned off. This

minimizes the potential for damage to power components during

certain faults and transient events.

TIMING CONSTRAINTS

Shutdown Time

When the ADP2126/ADP2127 enter shutdown mode after the

EXTCLK signal is removed, the ADP2126/ADP2127 must remain

in shutdown mode for a minimum of 1400 μs, if no load is applied,

before the EXTCLK signal can be reapplied. This allows all internal

nodes to discharge to an off state.

Output Short-Circuit Protection (SCP)

If the output voltage is shorted to GND, a standard dc-to-dc

controller delivers maximum power into that short. This may

result in a potentially catastrophic failure. To prevent this, the

ADP2126/ADP2127 sense when the output voltage is below the

SCP threshold (typically 0.52 V). At this point, the controller

turns off for approximately 450 μs and then automatically initiates a

soft start sequence. This cycle repeats until the short is removed

or the part is disabled. Figure 17 shows the operating behavior of

the ADP2126/ADP2127 during a short-circuit fault. The SCP

dramatically reduces the power delivered into the short circuit,

yet still allows the converter to recover when the fault is removed.

Power-Off Time

nodes to discharge enough power so that all internal devices are

in an off state.

Thermal Shutdown (TSD) Protection

Figure 30. Power-Off Time

The ADP2126/ADP2127 also include TSD protection when the

part is in PWM mode only. If the die temperature exceeds 146°C

(typical), the TSD protection activates and turns off both MOSFET

power devices. They remain off until the die temperature falls to

133°C (typical), at which point the regulator restarts.