LM5118 Quick Start Component Calculator

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```					LM5118 Quick Start Component Calculator
Note: The components calculated in this worksheet are reasonable starting values for a design
using the LM5118. They are not optimized for any particular performance attribute.                                                Operational Modes vs VIN
Step 1 - Application Requirements
45
Vout (V)    12
Enter design requirements in the shaded cells                               Vin(min) (V)     5                     40
Vin(max) (V)     40
Maximum Average Load Current Iout (A)         3                     35
Ripple Current as % of Maximum Load Current (%)       40%
VCCX Voltage (V)      0                     30                                                                    Buck

Vin at start of Transition to Buck-Boost Mode (V)    15.96                                                                                         Transition

VIN (Volts)
Buck-Boost Mode Operation      YES                     25                                                                    Buck-boost

20
Recommended Controller IC       LM5118
15
Step 2 - Switching Frequency
Maximum Possible Switching Frequency (kHz)        500                    10
Switching Frequency (kHz)        300
Timing Resistor, Rt (kW)      18.31                    5

Step 3 - Inductor Value                                                                                             0
Calculated Buck Mode Inductor Value, Lb (µH)      23.33
Calculated Buck-Boost Mode Inductor Value, Lb-b (µH)       9.80
Actual Chosen Inductor Value, L (µH)       10
Vin
Step 4 - Calculate Output and Inductor Currents Based on Chosen Inductor
Buck-Boost Ripple Current at Vin=Vout, ΔI (A)      2.00                                                                        VIN              VCC                7.79774309
Cvcc
Buck mode Ripple Current at Vin(max), ΔI (A)      2.80                         Ruv1                         CIN                                   HB
Buck-Boost Ripple Current at Vin(min), ΔI (A)     1.18                   EN
Buck-Mode Peak Inductor Current, Ip(b) (A)       4.40                                                                        EN                            Chb
Buck-Boost Mode Peak Inductor Current, Ip(b-b) (A)      10.79
UVLO                HO
Step 5 - Current Limit With Safety Margin; Recalculate Currents                                                                                                                                                                                                  Vou
Current Limit Margin (% beyond Max Load) (%)       20%                          Cr                                              SS                  HS
Ruv2
Current Sense Resistor, Rs (mW)      18.54                                                                                                                                 L
Closest Standard Value, Rs (mW)       15.0                                                      To VCC     Css          LM5118
Buck Mode Average Output Current Limit (A)       6.93                                                                                            CS
SYNC                                                                                                                                                COUT
Buck-Boost Mode Inductor Current Peak at Current Limit (A)    16.67
SYNC                                          RS
Buck-Boost Mode Average Output Current Limit (A)        4.73
RT               CSG
Step 5 - Ramp Capacitor
Cramp (pF)      333                              RT                             Rramp
Rramp (kW)      NA                                                                                              LO
R
RAMP
Step 9 - Output Capacitors (Based on Worst Case Conditions for Each Mode)                                                                                                                   FB
Cramp
Target output ripple (mV)        100
Buck-Boost Duty cycle at Vin(min) (%)       71%
Optional                                                                                      Czero Rcomp                                            Rf
Buck-Boost RMS Ripple Current in Output Cap (A)         3.20            External                                                    VCCX           COMP
Minimum COUT output Capacitor Value (µF)          70.59             Bias
Required COUT ESR (mW)             9.27                                                                        PGND
Chosen COUT output capacitor value (µF)          300
Buck Mode Output Ripple Voltage (mV)           18.5                                                                                                             Cpole
AGND

Step 10 - Input Capacitors (Based on Worst Case Conditions for Each Mode)
Buck-Boost RMS Input Ripple Current (A)         4.66
Buck-Boost Mode Peak to Peak Current Ripple in Input Cap (A)      10.20
Buck Mode RMS input Ripple Current (A)         1.37
Buck Mode Peak to Peak Current Ripple in Input Cap (A)       7.20
Initial Input Capacitor Value(μF)     27.78
Chosen CIN Input Capacitor Value (µF)          50

Step 10 - Feedback Resistors
Rfb1 (W)    300.00
Rfb2 (W)    2,626.8

Step 11 - Chb & Cvcc Capacitor
High-side MOSFET Qg at VGS=10V (nC)          30.00
Minimum Bootstrap Capacitor Chb (µF)       0.08                                                                    Overall Gain and Phase
Chosen Value for Chb (µF)        0.1
Minimum VCC Bypass Capacitor Cvcc (µF)           1
100                                                                         180
Step 12 - Error Amplifier Compensation
Right Half Plane Zero Frequency (kHz)       7.81                                               80                                                                          150
Phase Margin (Deg)

Bandwidth (kHz)       2.05
Modulator Gm (A/V)       6.18                                               60                                                                          120
Gain (dB)

Modulator Gain at Loop Crossover (dB)      -7.80
40                                                                          90
Target Error Amp Zero Frequency (Hz)        226
Tartet Error Amp Pole Frequency (Hz)     7,806                                                20                                                                          60
Rcomp (W)      6,758
Cpole (nF)       0.07                                                0                                                                          30
Czero (nF)     104.09
-20                                                                         0
Step 13 - Soft Start capacitor                                                                                                                    1.E+00       1.E+01    1.E+02    1.E+03        1.E+04      1.E+05    1.E+06
Choose soft-start time (ms)      12
Frequency (Hz)
Soft Start Capacitor Value (nF)    97.6

Step 14 - UVLO Threshold and Hiccup Mode Restart
Minimum Value of Resistor Ruv1 (kW)            40
Chosen Value of Ruv1 (kW)           75
Desired Undervoltage Threshold (V)           4
Ruv2 Value (kW)        29.33
Choose off-time of hiccup duty cycle (µs)      1000
Vin voltage for desired hiccup mode off-time (V)          12
Hiccup Mode Off-time Capacitor Value Cr (µF)          0.10
LM5118 List of Components

Component     Description                    Value
Cin        Input capacitor                50 μF
Cramp       Ramp capacitor                333 pF
Css        Soft start capacitor          97.6 nF
Cout       Output capacitor              300 μF
Cr        UVLO filter capacitor         0.10 μF
Cpole       Compensation capacitor         0.1 nF
Czero       Compensation capacitor       104.1 nF
Cvcc       VCC bypass capacitor          1.0 μF
Chb        HB-SW bypass capacitor        0.10 μF
Rfb1       Feedback resistor              300 Ω
Rfb2       Feedback resistor            2,627 Ω
Ruv1       UVLO divider resistor        75.0 kΩ
Ruv2       UVLO divider resistor        29.3 kΩ
Rs        Sense resistor               18.5 mΩ
Rt        Oscillator timing resistor   18.31 kΩ
L         Inductor                     10.0 μH
Rramp       Optional ramp resistor           NA
Rcomp       Compensation resistor         6.8 kΩ
Rating
100V, X7R
100V, COG
100V, X7R
16V, X7R
100V, X7R
100V COG
100V COG
25V, X7R
100V, X7R
1/16 W
1/16 W
1/16 W
1/16 W
2W
1/16 W
13A
-
1/16 W
Error     Error      Overall
Modulator              Modulator       Amplifier Amplifier    Loop                    Loop
Frequency Frequency      Gain                 Phase          Gain      Phase       Gain                    Phase
(Hz)   (rad/sec)     (dB)                  (deg)          (dB)     (deg)       (dB)                    (deg)
1.00E-01  6.28E-01    11.4110              -2.60E-02        75.30       90        86.71                     90
2.00E-01  1.26E+00    11.4110              -5.19E-02        69.28       90        80.69                     90
5.00E-01  3.14E+00    11.4110              -1.30E-01        61.32       90        72.73                     90
1.00E+00  6.28E+00    11.4110              -2.60E-01        55.30       90        66.71                     90
2.00E+00  1.26E+01    11.4107              -5.19E-01        49.28       91        60.69                     90
5.00E+00  3.14E+01    11.4089              -1.30E+00        41.32       91        52.73                     90
1.00E+01  6.28E+01    11.4026              -2.59E+00        35.31       93        46.71                     90
2.00E+01  1.26E+02    11.3773              -5.18E+00        29.31       95        40.69                     90
5.00E+01  3.14E+02    11.2041              -1.28E+01        21.53      103        32.73                     90
1.00E+02  6.28E+02    10.6368              -2.45E+01        16.07      114        26.71                     89
2.00E+02  1.26E+03     8.9063              -4.27E+01        11.79      132        20.69                     89
5.00E+02  3.14E+03     3.7326              -6.88E+01         9.02      156        12.75                     87
1.00E+03  6.28E+03    -1.6419              -8.36E+01         8.42      168         6.78                     84
2.00E+03  1.26E+04    -7.2913              -9.59E+01         8.26      174         0.97                     78
5.00E+03  3.14E+04   -13.9580              -1.15E+02         8.22      177        -5.74                     62
1.00E+04  6.28E+04   -17.1480              -1.31E+02         8.21      178        -8.94                     47
2.00E+04  1.26E+05   -18.2260              -1.39E+02         8.19      177       -10.03                     38
5.00E+04  3.14E+05   -16.7736              -1.30E+02         8.10      172        -8.67                     42
1.00E+05  6.28E+05   -13.2371              -1.15E+02         7.81      164        -5.43                     48
2.00E+05  1.26E+06    -8.1249              -1.04E+02         6.79      149        -1.33                     45
5.00E+05  3.14E+06    -0.4570              -9.56E+01         2.88      124         2.43                     28
1.00E+06  6.28E+06     5.5205              -9.28E+01        -2.06      109         3.46                     16

Modulator Gain/Phase
COMP to VOUT

60                                                                     0

40                                                                     -30

20                                                                     -60
Phase (deg)
Gain (dB)

0                                                                     -90

-20                                                                    -120

-40                                                                    -150

-60                                                                    -180
1.E+00   1.E+01   1.E+02       1.E+03       1.E+04     1.E+05     1.E+06
Frequency (Hz)

Error Amplifier Gain/Phase
VOUT to COMP

100                                                                     180

80                                                                     150
60                                                                 120

Phase (deg)
Gain (dB)
40                                                                 90

20                                                                 60

0                                                                 30

-20                                                                0
1.E+00   1.E+01   1.E+02       1.E+03       1.E+04   1.E+05   1.E+06
Frequency (Hz)
Mod RHP
pole at orgin Dominant mod                                    ModESRz                                ZERO
gain           pole                     ModRHP Zero          ero    error zero error hf pole     Phase
7.5300E+01    -8.48415E-07                 -7.13517E-10      1.33E-11 8.48E-07       -4.19E-13   -0.000734
6.9279E+01    -3.39366E-06                 -2.85407E-09      5.30E-11 3.39E-06       -1.67E-12   -0.001469
6.1321E+01    -2.12103E-05                 -1.78379E-08      3.31E-10 2.12E-05       -1.05E-11   -0.003672
5.5300E+01    -8.48407E-05                 -7.13517E-08      1.33E-09 8.48E-05       -4.18E-11   -0.007344
4.9279E+01    -0.000339353                 -2.85407E-07      5.30E-09 3.39E-04       -1.67E-10   -0.014688
4.1321E+01     -0.00212052                 -1.78379E-06      3.31E-08 2.12E-03       -1.05E-09    -0.03672
3.5300E+01    -0.008475875                 -7.13517E-06      1.33E-07 8.48E-03       -4.18E-09    -0.07344
2.9279E+01    -0.033804697                 -2.85406E-05      5.30E-07 3.38E-02       -1.67E-08    -0.14688
2.1321E+01    -0.207087031                 -0.000178376      3.31E-06 2.07E-01       -1.05E-07   -0.367195
1.5300E+01     -0.77496828                 -0.000713458      1.33E-05 7.75E-01       -4.18E-07    -0.73436
9.2793E+00     -2.50766124                 -0.002853131      5.30E-05 2.51E+00       -1.67E-06   -1.468478
1.3205E+00    -7.696630597                 -0.017801394      3.31E-04 7.70E+00       -1.05E-05   -3.666985
-4.7001E+00    -13.12504848                 -0.070771921      1.33E-03 1.31E+01       -4.18E-05   -7.304173
-1.0721E+01    -18.98406571                 -0.276420375      5.30E-03 1.90E+01       -1.67E-04   -14.37837
-1.8679E+01    -26.89652418                 -1.494449661      3.30E-02 2.69E+01       -1.05E-03    -32.6552
-2.4700E+01     -32.9104633                 -4.220862895      1.31E-01 3.29E+01     -4.183E-03    -52.03967
-3.0721E+01    -38.92939641                 -8.791954235      5.00E-01 3.89E+01     -1.671E-02    -68.68996
-3.8679E+01    -46.88772977                 -16.24007049      2.46E+00 4.69E+01     -1.034E-01    -81.13141
-4.4700E+01    -52.90826299                 -22.18255468      6.08E+00 5.29E+01     -3.995E-01    -85.53898
-5.0721E+01    -58.92884623                 -28.18340413      1.12E+01 5.89E+01 -1.416E+00        -87.76611
-5.8679E+01    -66.88764173                 -36.13665804      1.89E+01 6.69E+01 -5.326E+00        -89.10606
-6.4700E+01    -72.90824098                 -42.15646505      2.49E+01 7.29E+01 -1.027E+01           -89.553

Overall Gain and
Phase
100                                                                   180

80                                                               150

60                                                               120
Gain (dB)

40                                                               90

20                                                               60

0                                                               30

-20                                                              0
1.E+00   1.E+01   1.E+02     1.E+03     1.E+04   1.E+05   1.E+06
Frequency (Hz)
MOD
Dominate
MOD ESR Zero      Pole
0.000100109   -0.025324
0.000200218   -0.050648
0.000500545    -0.12662
0.001001091    -0.25324
0.002002181    -0.50647
0.005005453   -1.266001
0.010010905   -2.530767
0.020021809   -5.051697
0.050054513   -12.46177
0.100108949   -23.84493
0.200217288   -41.47601
0.500532523   -65.65328
1.00098866   -77.25148
2.001366648   -83.54586
4.992776597   -87.40914
9.910859664   -88.70391
19.2617896   -89.35187
41.1409916   -89.74074
60.21604126   -89.87037
74.03063503   -89.93518
83.46996065   -89.97407
86.72434322   -89.98704

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