Recalculate values for LP8867 and modify schematic and layout accordingly.
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@ -132,29 +132,29 @@ Wire Wire Line
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Wire Wire Line
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2900 3500 1850 3500
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Wire Wire Line
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1850 3500 1850 3700
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1850 3500 1850 4500
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$Comp
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L Device:R R12
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U 1 1 6060F6AC
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P 1850 3850
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F 0 "R12" H 1920 3896 50 0000 L CNN
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F 1 "33k" H 1920 3805 50 0000 L CNN
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F 2 "Resistor_SMD:R_0603_1608Metric" V 1780 3850 50 0001 C CNN
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F 3 "~" H 1850 3850 50 0001 C CNN
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1 1850 3850
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P 1850 4650
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F 0 "R12" H 1920 4696 50 0000 L CNN
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F 1 "39k" H 1920 4605 50 0000 L CNN
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F 2 "Resistor_SMD:R_0603_1608Metric" V 1780 4650 50 0001 C CNN
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F 3 "~" H 1850 4650 50 0001 C CNN
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1 1850 4650
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1 0 0 -1
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$EndComp
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Wire Wire Line
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1850 4000 1850 4150
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1850 4800 1850 4950
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$Comp
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L power:GND #PWR0143
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U 1 1 60610BC6
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P 1850 4150
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F 0 "#PWR0143" H 1850 3900 50 0001 C CNN
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F 1 "GND" H 1855 3977 50 0000 C CNN
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F 2 "" H 1850 4150 50 0001 C CNN
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F 3 "" H 1850 4150 50 0001 C CNN
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1 1850 4150
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P 1850 4950
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F 0 "#PWR0143" H 1850 4700 50 0001 C CNN
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F 1 "GND" H 1855 4777 50 0000 C CNN
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F 2 "" H 1850 4950 50 0001 C CNN
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F 3 "" H 1850 4950 50 0001 C CNN
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1 1850 4950
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1 0 0 -1
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$EndComp
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Wire Wire Line
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@ -194,7 +194,7 @@ L Device:R R11
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U 1 1 6061C45B
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P 1500 3850
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F 0 "R11" H 1430 3804 50 0000 R CNN
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F 1 "147k" H 1430 3895 50 0000 R CNN
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F 1 "56k" H 1430 3895 50 0000 R CNN
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F 2 "Resistor_SMD:R_0603_1608Metric" V 1430 3850 50 0001 C CNN
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F 3 "~" H 1500 3850 50 0001 C CNN
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1 1500 3850
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@ -223,8 +223,8 @@ L Device:L_Core_Ferrite L2
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U 1 1 60625C92
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P 3350 2400
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F 0 "L2" V 3575 2400 50 0000 C CNN
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F 1 "DE1205-33" V 3484 2400 50 0000 C CNN
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F 2 "shimatta_inductor:FerroCore_DE1205" H 3350 2400 50 0001 C CNN
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F 1 "DE0704-22" V 3484 2400 50 0000 C CNN
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F 2 "shimatta_inductor:FerroCore_DE0704" H 3350 2400 50 0001 C CNN
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F 3 "https://www.tme.eu/Document/d1f8b47d020ebf11f3b92c6891638dfa/de.pdf" H 3350 2400 50 0001 C CNN
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1 3350 2400
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0 -1 -1 0
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@ -345,7 +345,7 @@ L Device:R R10
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U 1 1 6064ADF7
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P 5800 3000
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F 0 "R10" V 5593 3000 50 0000 C CNN
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F 1 "130k" V 5684 3000 50 0000 C CNN
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F 1 "100k" V 5684 3000 50 0000 C CNN
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F 2 "Resistor_SMD:R_0603_1608Metric" V 5730 3000 50 0001 C CNN
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F 3 "~" H 5800 3000 50 0001 C CNN
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1 5800 3000
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@ -356,7 +356,7 @@ L Device:R R9
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U 1 1 6064B526
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P 5800 2600
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F 0 "R9" V 5593 2600 50 0000 C CNN
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F 1 "680k" V 5684 2600 50 0000 C CNN
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F 1 "560k" V 5684 2600 50 0000 C CNN
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F 2 "Resistor_SMD:R_0603_1608Metric" V 5730 2600 50 0001 C CNN
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F 3 "~" H 5800 2600 50 0001 C CNN
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1 5800 2600
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@ -389,7 +389,7 @@ L Device:C C57
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U 1 1 60654433
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P 6000 2600
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F 0 "C57" H 6115 2646 50 0000 L CNN
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F 1 "10p" H 6115 2555 50 0000 L CNN
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F 1 "14p" H 6115 2555 50 0000 L CNN
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F 2 "Capacitor_SMD:C_0603_1608Metric" H 6038 2450 50 0001 C CNN
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F 3 "~" H 6000 2600 50 0001 C CNN
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1 6000 2600
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@ -875,7 +875,7 @@ Wire Wire Line
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Wire Wire Line
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4300 5650 7350 5650
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Text Notes 7700 2650 0 50 ~ 0
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LEDs: L128-4095HA3500001\nVf: 3V\nIf: ~~70 mA
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LEDs: L128-4095HA3500001\nVf: 3V\nIf: ~~60 mA
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Text Notes 5550 2250 0 50 ~ 0
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V = ~~ 24V
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Text Notes 5550 2350 0 50 ~ 0
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@ -926,4 +926,12 @@ F 3 "~" H 6650 2000 50 0001 C CNN
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$EndComp
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Wire Wire Line
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6450 2000 6450 2400
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Text Notes 3250 2100 0 50 ~ 0
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22 uH
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Text Notes 2150 4650 0 50 ~ 0
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Max Current = 60 mA
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Text Notes 850 3900 0 50 ~ 0
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f = 1.08 MHz
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Text Notes 1650 1850 0 50 ~ 0
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For the calculation of the component values see 'lp8867-calc.py'
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$EndSCHEMATC
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@ -0,0 +1,98 @@
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#!/bin/python
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import numpy as np
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import eseries as es
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def calc_fsw_from_r_fset(r_fset):
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fsw = 67600 / (r_fset / 1e3 + 6.4)
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fsw = fsw * 1e3
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return fsw
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def calc_r_fset_from_fsw(fsw):
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fsw = fsw / 1e3
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r = 67600 / (fsw) - 6.4
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r = r * 1e3
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return r
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def calc_r_iset_from_i(i):
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i = i * 1e3
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r = 2000 * 1.2 / i
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r = r * 1e3
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return r
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def calc_i_from_r_iset(r):
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r = r * 1e-3
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i = 2000 * 1.2 / r
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i = i * 1e-3
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return i
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def calc_vout(r1, r2, k):
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r1 = r1 / 1000
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r2 = r2 / 1000
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v = (1.2 / r2 + k * 0.0387) * r1 + 1.2
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return v
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switching_freq = 1.1e6
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output_voltage_nom = 24 + 0.9
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inductor_value = 22e-6
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input_voltage = 12
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output_current_per_lane = 60e-3
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desired_e_series = es.E12
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r1 = 560e3
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r2 = 100e3
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# Calculate the parameters
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print('Calculating for the given parameters:')
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print(f'{switching_freq = }')
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print(f'{output_voltage_nom = } and {input_voltage = }')
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print(f'{inductor_value =}')
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print(f'{desired_e_series = }')
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print('')
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rfset = calc_r_fset_from_fsw(switching_freq)
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print(f'{rfset = }')
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# Find the nearest value in the e series
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rfset = es.find_nearest(desired_e_series, rfset)
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f_sw = calc_fsw_from_r_fset(rfset)
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print(f'The nearest value from the E series is: {rfset = }')
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freq_error = (f_sw - switching_freq) / switching_freq * 100
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print(f'Resulting switching frequency is {f_sw} (Error: {freq_error:.1f} %)')
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print(f"Desired output current per lane is {output_current_per_lane} A")
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r_iset = calc_r_iset_from_i(output_current_per_lane)
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print(f'Resulting in {r_iset = }')
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r_iset = es.find_nearest(desired_e_series, r_iset)
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output_current_per_lane = calc_i_from_r_iset(r_iset)
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print(f'Nearest e series value {r_iset = } resulting in an LED current of {output_current_per_lane} A')
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d = (output_voltage_nom - input_voltage) / output_voltage_nom
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d_inv = 1-d
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print(f"Expected duty cycle: {d}")
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i_ripple = (output_voltage_nom- input_voltage) / (2 * inductor_value * f_sw) * (input_voltage / output_voltage_nom)
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print(f'Ripple current: {i_ripple} A')
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i_sat_min = output_current_per_lane * 4 / d_inv + i_ripple
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print(f'Minimum saturation current of inductor: {i_sat_min:.3f} A')
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print(f'Voltage divider {r1 = } | {r2 = }')
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print(f'Output voltage initial: {calc_vout(r1, r2, 0.88)} V')
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print(f'Output voltage maximum: {calc_vout(r1, r2, 1)} V')
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print(f'Output voltage minimum: {calc_vout(r1, r2, 0)} V')
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ovp = output_voltage_nom + (r1/r2 + 1)*(2.3 - 1.2)
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print(f'Over voltage protection: {ovp} V')
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ratio = r1/r2
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print(f'Resistance ratio is {ratio}')
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if f_sw <= 1150e3:
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ratio_range = (5, 10)
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else:
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ratio_range = (10, 20)
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if ratio < ratio_range[0] or ratio > ratio_range[1]:
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print('Ratio is outside recommended limits!')
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# Loop stability
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cfb = 1 / (2 * np.pi * 20e3 * r1 )
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print(f'Loop stability capacitor value: {cfb} F')
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File diff suppressed because it is too large
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