LM5145 datasheet(38/70 Pages) TI

38 / 70 page

2. Use Equation 39 to calculate the input capacitor RMS ripple current assuming a worst-case duty-cycle

operating point of 50%.

CIN(RMS)

OUT

D 1 D

0.5 1 0.5

4 A

(39)

3. Use Equation 40 to find the required input capacitance.

˜ '

: ˜

OUT

ESR

OUT

1 D

0.5

8 A

9.2

)

2.1MHz

120mV

8 A

(40)

where

• ΔVIN is the input peak-to-peak ripple voltage specification.

• RESR is the input capacitor ESR.

4. Recognizing the voltage coefficient of ceramic capacitors, select two 10-µF, 50-V, X7R, 1210 ceramic input

capacitors. Place these capacitors adjacent to the power MOSFETs. See Section 9.4.1.1 for more details.

5. Use four 10-nF, 50-V, X7R, 0603 ceramic capacitors near the high-side MOSFET to supply the high di/dt

current during MOSFET switching transitions. Such capacitors offer high self-resonant frequency (SRF)

and low effective impedance above 100 MHz. The result is lower power loop parasitic inductance, thus

minimizing switch-node voltage overshoot and ringing for lower conducted and radiated EMI signature. Refer

to Section 9.4.1 for more details.

9.2.1.2.7 Frequency Set Resistor

Calculate the RT resistance for a switching frequency of 2.1 MHz using Equation 41. Choose a standard E96

value of 9.53 kΩ.

(kHz)

2100kHz

R (k )

9.4k

(41)

9.2.1.2.8 Feedback Resistors

If an output voltage setpoint other than 3.3 V or 5 V is required (or to measure a bode plot when using either of

the fixed output voltage options), determine the feedback resistances using Equation 42.

(42)

9.2.1.2.9 Compensation Components

Choose compensation components for a stable control loop using the procedure outlined as follows:

1. Based on a specified loop gain crossover frequency, fC, of 60 kHz, use Equation 43 to calculate RCOMP,

assuming an effective output capacitance of 100 µF. Choose a standard value for RCOMP of 10 kΩ.

: ˜

OUT

COMP

OUT

REF

5 V

60kHz

100 )

0.8 V 1200 6

(43)

2. To provide adequate phase boost at crossover while also allowing a fast settling time during a load or line

transient, select CCOMP to place a zero at the higher of (1) one tenth of the crossover frequency, or (2) the

load pole. Choose a standard value for CCOMP of 2.7 nF.

COMP

2.65 nF

60 kHz 10 k

(44)

LM5148

SNVSC01 – FEBRUARY 2023

www.ti.com

Submit Document Feedback

Product Folder Links: LM5148

LM5145 Datasheet(PDF) 38 Page - Texas Instruments

LM5145 Datasheet(HTML) 38 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 61 62 63 64 65 66 67 68 69 70

Datasheet Download

Link URL