LTM4719 datasheet(42/53 Pages) AD

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Data Sheet

LTM4719

analog.com

Rev. 0

42 of 53

Current Limit and Thermal Overload Protection

The LTM4719 is protected against damage due to excessive power dissipation by current and thermal overload

protection circuits. The LTM4719 is designed to the current limit when the output load reaches 320mA (typical). When

the output load exceeds 320mA, the output voltage is reduced to maintain a constant current limit.

Thermal overload protection is included, which limits the junction temperature to a maximum of 150°C (typical).

Under extreme conditions (that is, high ambient temperature and power dissipation), when the junction

temperature starts to rise above 150°C, the output is turned off, reducing the output current to zero. When the

junction temperature drops below 135°C, the output is turned on again, and the output current is restored to its

nominal value.

VOC Capacitor Selection

A minimum value of capacitance (COC) is required between VOC and ground. This capacitor determines the IPEAK pulse

on and off durations. Its value should be selected based on the maximum current load at the VOC pin and the IPEAK

setting. For best coulomb counter accuracy, it is recommended to have 50μs minimum IPEAK on/off durations (see

Equation 19).

��_�� (min) =

�� × ��_��

��

(19)

��_�� (min) =

�� × ��_��

��(��)

where VHYST_OC is the voltage ripple value between VOC_HIGHand VOC_LOW. See Figure 20. The hysteresis is nominally set to

50mV.

For the 100mA IPEAK setting and a maximum load current of 100mA, a 100μF COC capacitor is recommended. See Table

17 for recommended COC values for the other IPEAK settings.

Table 17.Recommended Minimum COC Values for Each IPEAK Selection

IPK2

IPK1

IPK0

IPEAK

(mA)

RECOMMENDED COC

(μF)

4.7

100

The VOC_HIGH and VOC_LOW thresholds are DC levels. The actual AC values seen in application will be outside of these

levels due to finite delay in the hysteretic comparator.

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