R34DS0034EU0101 Rev.1.01

Page 20

Mar 13, 2024

ISL73006SLH Datasheet

respectively, for the intended duty cycle. The timing constraints mostly impact extremely high or low-duty cycle

conversions where the minimum off and on times are infringed up. Changing PVIN is the simple method to

alleviate minimum on-time and off-time concerns.

5.6

Overcurrent Protection

Overcurrent protection (OCP) is provided for the sourcing and sinking output current conditions. An accurate

current-sensing pilot device parallel to the upper MOSFET is used for peak current control signal and overcurrent

protection. Current is sensed and monitored on the output current ripple at the most positive peak and negative

valley amplitudes for the sourcing and sinking conditions. An excessive ripple current lowers the DC output

current capability because of the peak detection used for OCP. OCP is triggered if the OCP threshold is exceeded

in four of the eight preceding switching periods. On the 4th current peak above the OCP threshold, the device

enters the fault state, stops switching, and the output is pulled low by the output loading. The device attempts to

turn on again in a hiccup mode, and when the overcurrent condition goes away, the output soft starts again into a

regulated output voltage. The typical sourcing OCP threshold is invoked at less than 2x the rated output current of

1A, providing headroom for the peak ripple current.

During the soft-start period, there is an additional level of overcurrent protection of a single instance at ~2A to protect

against shorted or otherwise damaged loads. When invoked, this fault goes into hiccup restart cycling until a

successful restart occurs.

5.7

Negative Overcurrent Protection (NOCP)

If an external source drives current into the VOUT pin, the controller attempts to regulate the output voltage by

reversing its inductor current to absorb the externally sourced current. If the external source is low-impedance, it

might reverse the current to an unacceptable level, and the controller initiates its negative overcurrent limit

protection. The negative overcurrent protection is realized by monitoring the current through the lower FET.

When the valley point of the inductor current reaches the negative current limit of typically -1.8A, the NOCP fault is

declared, and the LX out goes into a high-Z state. The IC enters into a hiccup mode to restart. There is no valley

current counter on the NOCP function.

5.8

Power Good

Power-Good (PG) is the output of a window comparator that continuously monitors the buck regulator output

voltage. The PG output is actively held low when EN is low and during the buck regulator soft-start period. After

soft-start completes, the PG pin becomes high impedance as long as the output voltage is in nominal regulation of

the output voltage. When VFB is typically beyond ±6% of the nominal regulation voltage for ~5µs, the device open

drain output pulls the PG output low. Add an external resistor from PG to a maximum of the PVIN voltage for PG

signaling purposes.

5.9

UVLO, Enable, Soft-start, Disable and Soft-Stop

When PVIN is below the Undervoltage Lockout (UVLO) threshold, the regulator is inert until PVIN rises above the

UVLO voltage of ~2.86V. The ISL73006SLH Enable pin provides three states of operation. Below the standby

threshold (typically 0.68V), the ISL73006SLH is disabled and draws a typical 105µA from PVIN. The VCC LDO

can start up with the EN pin between a typical 1.0V and 1.2V, and the part enters a standby state. Normal

switching operation and soft-start begin when the EN pin is over 1.2V.

During startup, the ISL73006SLH critiques for Overvoltage (OV) and Over-Temperature (OT) faults and remains

idle if either fault is active. The soft-start time relates to the operating switching frequency during startup. There is

a delay from enable active to LX activity during which the ISL73006SLH internal circuitries are biased. The

ISL73006SLH can seamlessly start into a pre-biased output, provided the output voltage is below the set

regulation voltage. If the pre-biased output exceeds the regulation set point, the ISL73006SLH does not initiate LX

switching but turns on the low-side MOSFET to pull the output down. Suppose the sinking output current reaches

the negative output current limit (NOCL). In that case, it enters hiccup operation until the output is below the

regulation set point and then proceeds through soft-start to LX switching. If the sinking output current does not