LT3758 datasheet(22/28 Pages) AD

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LT8392

Rev. 0

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Figure 14. Programming Output Current Limit

LT8392

ISP

8392 F14a

ISN

RIS

TO SYSTEM

OUTPUT

FROM DRAIN OF

SWITCH D

LT8392

ISP

8392 F14b

ISN

RIS

TO SYSTEM

OUTPUT

FROM DRAIN OF

SWITCH D

(14a)

(14b)

APPLICATIONS INFORMATION

the current loop. Since the bias currents of the ISP and

ISN pins are matched, no offset is introduced by RF. If

input or output current limit is not used, the ISP and ISN

pins should be shorted to VIN, VOUT, or ground.

ISMON Current Monitor

The ISMON pin provides a buffered monitor output of

the current flowing through the ISP/ISN current sense

resistor, RIS. The VISMON voltage is calculated as V(ISP-ISN)

• 20 + 0.25V. Since the ISMON pin has the same 0.25V

offset as the CTRL pin, the master LT8392 ISMON pin can

be directly tied to the slave LT8392 CTRL pin for equal

current sharing in parallel applications.

Programming Output Voltage and Thresholds

The LT8392 has a voltage feedback pin FB that can be

used to program a constant-voltage output. The output

voltage can be set by selecting the values of R3 and R4

(Figure 15) according to the following equation:

LT8392

VOUT

8392 F15

Figure 15. Feedback Resistor Connection

VOUT = 1V •

+R4

In addition, the FB pin also sets output overvoltage

threshold, output power good thresholds, and output

short threshold. For an application with small output

capacitors, the output voltage may overshoot a lot during

load transient event. Once the FB pin hits its overvoltage

threshold 1.08V, the LT8392 stops switching by turning

off TG1, BG1, TG2, and BG2, and also turns off EXTVCC

to disconnect the output load for protection. The output

overvoltage threshold can be set as:

VOUT(OVP) = 1.08V •

R3+R4

To provide the output short-circuit detection and protec-

tion, the output short falling threshold can be set as:

VOUT(SHORT) = 0.25V •

+R4

Power GOOD (PGOOD) Pin

The LT8392 provides an open-drain status pin, PGOOD,

which is pulled low when VFB is within ±8% of the 1.00V

regulation voltage. The PGOOD pin is allowed to be pulled

up by an external resistor to INTVCC or an external voltage

source of up to 6V.

Soft-Start and Short-Circuit Protection

As shown in Figure 8 and explained in the Operation sec-

tion, the SS pin can be used to program the output voltage

soft-start by connecting an external capacitor from the

SS pin to ground. The internal 12.5µA pull-up current

charges up the capacitor, creating a voltage ramp on the

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