L6739 datasheet(15/30 Pages) STMICROELECTRONICS

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L6739

Output voltage setting and protections

When overcurrent protection is triggered, the device turns off both LS and HS MOSFETs in

a latched condition.

To recover from an overcurrent protection triggered condition, VCC power supply or EN

must be cycled.

For proper current reading, the CSN pin must be filtered by 100 nF (typ.) MLCC to GND.

Note:

The device features an integrated OC thermal compensation in order to reduce the

influence of the temperature change of the inductor DCR. The internal temperature

coefficient compensation is 4000 ppm/°C (0.4%/°C).

Overcurrent threshold setting

The L6739 device detects OC when the difference between CSP and CSN is equal to

20 mV (typ.). By properly designing the current reading network, it is possible to program

the OC threshold as desired (See Figure 6).

Equation 4

Time constant matching is, in this case, designed considering:

Equation 5

This means that once inductor has been chosen, the two conditions above define the proper

values for R1 and R2.

Figure 6. Current reading network

IOCP

20mV

DCR

----------------

R1 R2

----------------------



DCR

-------------

R1//R2

 C



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