MAX20796 datasheet(21/33 Pages) MAXIM

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Overcurrent Protection (Power Stage Peak OCP)

Besides average OCP, the MAX20796 has the instan-

taneous cycle-by-cycle peak current protection in each

power train. The internal lossless current sense tech-

nology is used and intended to operate only in extreme

overcurrent conditions to protect the integrated FETs. Its

threshold is fixed as shown in the Electrical Characteristics

table. Once the power-stage peak OCP is triggered, the

relevant phase turns off the high-side FET and turns on its

low-side FET to keep its peak current at a safe level. Since

the protection is based on the instantaneous current,

the ripple current must be considered when calculating

the maximum average current per phase. The maximum

positive DC-phase current before clamping can be calcu-

lated as shown in Equation 2.

Equation 2:

PH_P-P

PHASE_DC_MAX_POS

FOCP_P

−

Where: IPH_P-P is the peak-to-peak phase-current ripple

in the inductor.

MAX20796 also has a negative cycle-by-cycle overcurrent

protection (NOCP) for each power train. Its threshold is

also fixed as shown in the Electrical Characteristics table.

If the NOCP threshold is reached, the low-side FET turns

off and the high-side FET turns on for protection. Equation

3 shows the maximum negative DC current per phase.

Equation 3:

PH,PP

PHASE_DC_MAX_NEG

NOCP

Undervoltage Lockout (UVLO)

The MAX20796 includes UVLO circuits on the AVDD,

VCC_, and VDDH_ supply input pins. The UVLO thresh-

olds are specified in the Electrical Characteristics table. If

a UVLO event is detected, the system stops regulating.

Once the faulted input voltage rises above its UVLO rising

threshold, the device reinitializes a new startup process.

Overtemperature Protection (OTP)

Overtemperature protection ensures the power train

as well as the controller works within a safe tem-

perature range. There are two temperatures monitored

in the MAX20796. READ_TEMPERATURE_1 reports

the integrated power train junction temperature. If

there is an external power stage connected, READ_

TEMPERATURE_2 reports its junction temperature by

monitoring the TS_FAULT pin voltage. If any temperature

is over the programmed threshold, the fault is triggered.

The regulator shuts down switching immediately by

turning off both FETs, waiting for about 50ms off time,

and then restarting if the junction temperature drops

below threshold. STATUS_TEMPERATURE is flagged to

report the fault. The factory default threshold is typically

150°C and it can be programmed using the PMBus com-

mands. OT_FAULT_RESPONSE can be programmed

to “Shutdown and Retry” (factory default) or “Shutdown

only.”

Fault Handling Table

The following table summarizes the fault types and sys-

tem responses. “Configurable” means some of these

options, “ignore,” “shutdown” and “shutdown and retry,”

can be selected through PMBus. See

Application Note

6453: MAX20796 PMBus User Guide for details.

Table 3. Fault Handling

FAULT

PROTECTION

STATUS

RESPONSE

FAULT LIMIT

A/DVDD UVLO

N/A

Reset

N/A

VCC_ UVLO

ALERT

STATUS_MFR_

SPECIFIC

Stop regulating until

UVLO condition

clears

N/A

VDDH_ UVLO

ALERT

STATUS_INPUT

Shutdown and retry N/A

N/A

BST_ UVLO

ALERT

STATUS_MFR_

SPECIFIC

Stop regulating until

UVLO condition

clears

N/A

VOUT Tracking

OVP

ALERT / PGOOD

STATUS_VOUT

Configurable

VOUT_OV_FAULT_

RESPONSE

VOUT_OV_FAULT_

LIMIT

VOUT Umbrella

OVP

ALERT / PGOOD

STATUS_VOUT

Configurable

VOUT_OV_FAULT_

RESPONSE

Fixed

VOUT UVP

ALERT / PGOOD

STATUS_VOUT

Configurable

VOUT_UV_FAULT_

RESPONSE

VOUT_UV_FAULT_

LIMIT

MAX20796

Dual-Phase Scalable Integrated Voltage

Regulator with PMBus Interface

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