Data Sheet

LT8342

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Rev. 0

21 of 36

The LT8342's protection features include output over-voltage and short-circuit protection, thermal shutdown, and

under-voltage lockout. The IC also prevents inductor current runaway in conditions requiring extremely low

converter duty cycles by adjusting switching frequency to maintain volt-second balance of the inductor.

APPLICATIONS INFORMATION

Programming VIN Turn-On and Turn-Off Thresholds with the EN/UVLO Pin

System VIN turn-on/-off thresholds can be programmed by driving the EN/UVLO pin with a resistor divider

connected from VIN to GND (See Block Diagram). The threshold voltages are determined by equations (1) and (2).

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������1 + ������2

������2

(1)

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������1 + ������

2

������2

(2)

When in Burst Mode operation with light load currents, the current through the resistor network R1 and R2 can

easily be greater than the supply current consumed by the LT8342. Therefore, R1 and R2 should be large to minimize

their effect on efficiency at low loads.

The EN/UVLO pin can be connected to VIN if the shutdown feature is not used, or alternatively, the pin may be tied

to a logic level if shutdown control is required. The IC draws a low VIN quiescent current of 0.35μA (typical) when

EN/UVLO is below 0.15V.

INTVCC Regulator

An internal low dropout (LDO) regulator produces the 3.6V supply from VIN that powers the gate drivers and the

internal bias circuitry. The INTVCC pin must be bypassed to GND with a minimum of 2.2μF ceramic capacitor. Good

bypassing is necessary to supply the high transient currents required by the power MOSFET gate drivers.

Applications with high input voltage and high switching frequency will increase die temperature because of the

higher power dissipation across the LDO. Do not connect any external load to the INTVCC pin.

Programming the Output Voltage

LT8342 features an adjustable internal feedback divider which programs the regulated output voltage level.

Configuring VSET1 and VSET2/FB pins as shown in Table 6 to select the preset level. The >10MΩ (typical) resistor

divider guarantees that the quiescent current from the VOUT pin is much reduced compared with a conventional

external potential divider.

In some applications where external feedback is still desired, one can tie the VSET1 pin to INTVCC through a 100kΩ

resistor, which programs the VSET2/FB pin as the conventional feedback pin. In this case, the output voltage is

programmed with a resistor divider between the output and the VSET2/FB pin, as shown in Figure 1. Choose the

resistor values according to the equation (3).

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������������������������

1������

− 1)

(3)

The resistance in equation (3) refer to reference designators in Figure 42. The 1% resistors are recommended to

maintain output voltage accuracy. When using large feedback resistors, a 4.7pF to 22pF phase-lead capacitor may

be required from VOUT to VSET2/FB. Note that when external feedback is used, if the fault occurs where VSET2/FB is

short to ground, instead of producing an excessively high output voltage, as shown in Table 6, LT8342 will

automatically switch to internal feedback with 19V output regulation.