Data Sheet

LT8350S

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Rev. A

30 of 36

The presence of a time varying differential voltage ripple signal across ISP and ISN at the switching frequency is

expected. The amplitude of this signal is increased by a higher load current, lower switching frequency, or smaller

value output filter capacitor. Some level of ripple signal is acceptable, and the compensation capacitor on the VC

pin filters the signal so the average difference between ISP and ISN is regulated to the user-programmed value. The

ripple voltage amplitude (peak-to-peak) in excess of 20mV should not cause misoperation but may lead to a

noticeable offset between the average value and the user-programmed value.

ISMON Current Monitor

The ISMON pin provides a buffered monitor output of the current flowing through the ISP/ISN current sense

resistor, RIS. The ISMON voltage is calculated as:

VISMON = 10 x V(ISP-ISN) + 250mV

Since the ISMON pin has the same 0.25V offset as the CTRL pin, the primary LT8350S ISMON pin can be directly

connected to the secondary LT8350S pin for equal current sharing in parallel applications.

LOAD Switch control

The LOADEN and LOADTG pins provide high-side p-channel metal-oxide semiconductor (PMOS) load switch

control. The LOADEN pin accepts a logic level ON/OFF signal and then drives the LOADTG pin to turn on or off the

high-side PMOS load switch, thereby connecting or disconnecting the LT8350S power output from the system

output. When the LOADEN pin is forced low, the LT8350S turns off power switches, disconnects the VC pin from all

internal loads, and turn off LOADTG. The LOADEN pin should not be open (connect to INTVCC or VREF if not used).

High Side PMOS Load Switch Selection

A high-side PMOS load switch is recommended in some LT8350S applications requiring load switch control. The

high-side PMOS load switch is typically selected for drain-source voltage VDS, gate-source threshold voltage VGS(TH),

and continuous drain current ID. For proper operations, VDS rating should exceed the maximum output voltage set

by the FB pin, the absolute value of VGS(TH) should be less than 3V, and ID rating should be above IOUT(MAX).

Programming Output Voltage and Thresholds

The LT8350 has a voltage feedback pin FB that can be used to program a constant-voltage output. The internal

error amplifier with its output VC regulates VFB to 1V through the DC/DC converter.

The output voltage can be set by selecting the values of R3 and R4 (Figure 40) according to the following equation:

VOUT = 1V ×

R3 + R4

R4

Figure 40. Feedback Resistor Connection

FB

LT8350S

GND

R4

R3

VOUT