LM5177DCPR datasheet(27/60 Pages) TI2

27 / 60 page

At the beginning of the soft-start sequence, the SS voltage is 0 V. If the SS pin voltage is below the feedback

reference voltage, VREF, the soft-start pin controls the regulated FB voltage and the internal soft-start current

source gradually increases the voltage on an external soft-start capacitor connected to the SS pin, resulting in

a gradual rise of the output voltage and FB pin. Once the voltage on the SS exceeds the internal reference

voltage, the soft-start interval is complete and the error amplifier is referenced to V(REF).

The soft-start time (t(ss)) is given by:

CSS= ISS×tSSVRef

(14)

The soft-start capacitor is internally discharged when the converter is disabled because of the following:

• EN/UVLO falling below the operating threshold

• VCC falling below the VCC UV threshold

• The device is in hiccup mode current limiting.

• The device is in thermal shutdown.

7.3.12 Peak Current Sensor

The integrated peak current sensor enables a low inductive sensing. The sensor is located in series with the

main inductor and can also can monitor the peak inductor current under all operation modes (boost, buck-boost

and buck) as well as for both current directions i.e. the bi-directional operation.

As the integrated sensor supports high bandwidth signals a differential mode filter adopted to the selected

operating point is recommended for best performance. For most applications we recommend a resistor value for

R(DIFF1/2) of 10Ω. You can use the equation below to determine the filter capacitor:

CDIFF = ton,min

2π∙ RDIFF1 +RDIFF2 ∙10

(15)

The differential filter can be set to a 10th of the minimum on-time of Buck or Boost mode.

Current sense resistors consist a parasitic inductance based on geometry and the selected component vendors

design. If the desired application requires high currents the impact of the external component parasitic can be

reduced by placing multiple sense resistors in parallel.

–

HB1

Peak Current

Comparator

R(CS) Sense resistor

equivalent circuit

CSA

CSB

SW1

Main Inductor

V(SW2)

V(SW1)

R(DIFF1)

R(DIFF2)

C(DIFF)

Figure 7-15. Simplified Schematic of the peak current sensor

7.3.13 Current Monitoring and Current Limit Control Loop

The LM5177 features two high voltage current sensors. The first one maintains the peak current sensing

between the CSA and CSB pins. The second current sensor inputs are connected to the ISNSP and ISNSN

pins.

www.ti.com

LM5177

SNVSBU4F – JUNE 2022 – REVISED JANUARY 2025

Submit Document Feedback

Product Folder Links: LM5177

LM5177DCPR Datasheet(PDF) 27 Page - Texas Instruments

LM5177DCPR Datasheet(HTML) 27 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Datasheet Download

Link URL