resistor-feedback-dat

MP1584-dat

0.8V FB

Vout = Vref * (R1/R2+1)

R2 ==

0.6V FB dcdc-bulk-output-dat

when Vref = 0.6V

Vout = Vref * (R2/R3+1)

for 5V = 0.6V * (100K / ? + 1 )

100K / R3 = 5V/0.6V - 1 = 7.3333 100K / R3 = 5.2V/0.6V - 1 = 7.6666

R3 = 13.633K or below 13.3K for 5.2V

output	rough	Rbot	Rtop	Vref
5V	5.18V	13.3K	100K	0.6V
5V	5.31V	13K	100K	0.6V
4.35V	4.35V	16K	100K	0.6V
4.2V	4.2V	16.6K	100K	0.6V
4V	3.93V	18K	100K	0.6V

1.2V FB = VBAT＝1.205×(1＋R1／R2)

电池端对应的的电压为： VBAT＝1.205×(1＋R1／R2)

R2 = ( R1 x 1.221 ) / ( VOUT - 1.221 )

= ( 10K x 1.221 ) / ( 5V - 1.221 ) = 3.23K ~ 3.24K

VOUT = ( R1 x 1.221 ) / R2 + 1.221 = ( 10K x 1.221 ) / 3.3K + 1.221 = 4.921V = ( 10K x 1.221 ) / 3K + 1.221 = 5.27V

= ( 12K x 1.221 ) / 3.3K + 1.221 = 5.661V

= ( 12K x 1.221 ) / 3.9K + 1.221 = 4.95V = ( 12K x 1.221 ) / 4.7K + 1.221 = 4.34V = ( 13K x 1.221 ) / 3K + 1.221 = 6.48V = ( 14K x 1.221 ) / 4.7K + 1.221 = 5.61V

= ( 9.1K x 1.221 ) / 2.8K + 1.221 = 5.19V

parallel resistor

https://www.digikey.cn/zh/resources/conversion-calculators/conversion-calculator-parallel-and-series-resistor

1.205 x ( 1 + R4 ∕ R5) parallel

R1	R2	Rsum
2M	820K	581K
2M	845K	594K
1.8M	845K	575K
1.6M	910K	580K
2M	1.8M	947K
1.2M		1.2M
2M		2M

2x 1.88 MΩ in parallel ≈ 940 kΩ.

1 MΩ and 15.67 MΩ in parallel ≈ 940 kΩ.

2 MΩ and 3.714 MΩ in parallel ≈ 1.3 MΩ.

3x 3.9 MΩ resistors in parallel = 1.3 MΩ

1.205 x ( 1 + R4 ∕ R5) series

for - LFP-dat

= 1.205 x ( 1 + 510k ∕ 100k) = 1.205 ⅹ 6.1 = 7.36V
= 1.205 x ( 1 + 800k ∕ 100k) = 1.205 ⅹ 9 = 10.845V
= 1.205 x ( 1 + 1000k ∕ 90k) = 1.205 ⅹ 12.11 = 14.6V

1.25 x ( 1 + R2 / R1 ) series

XL7015-dat

R2 == 30K, R1 == 2.7K VOUT == 15.14V

R2 / (12V /1.25 - 1) == 3.5K
R2 / (5V /1.25 - 1) == 10K

li-battery

resistor-feedback

8.4V

if R5 = 100k, R4 = 576k, voltage = 1.205 x (1 + 576k / 100k) = 8.14V
if R5 = 100k, R4 = 604k, voltage = 1.205 x (1 + 604k / 100k) = 8.48V
if R5 = 110k, R4 = 576k, voltage = 1.205 x (1 + 576k / 110k) = 7.515V
if R5 = 95.3k, R4 = 576k, voltage = 1.205 x (1 + 576k / 95.3k) = 8.488V
if R5 = 97.6k, R4 = 576k, voltage = 1.205 x (1 + 576k / 97.6k) = 8.316

12.6V

if R5 = 97.6k, voltage = 12.6V, R4 = (12.6 / 1.205 - 1) * R5 = 946k, use 923k
if R5 = 97.6k, R5 = 910K, voltage = 1.205 x (1 + 910k / 97.6k) = 12.44V

16.8V

if R5 = 97.6k, voltage = 16.8V, R4 = (16.8 / 1.205 - 1) * R5 = 1263k, use 1.2M
if R5 = 97.6k, R4 = 1.2M, voltage = 1.205 x (1 + 1200k / 97.6k) = 16.02V

6 * 4.2 = 25.2V

if R5 = 97.6k, R4 = 2M, voltage = 1.205 x (1 + 2000k / 97.6k) = 25.9V
if R5 = 100 k, R4 = 2M, voltage = 1.205 x (1 + 2000k / 100k) = 25.3V

obseleted

R4	R5	target Vout	actual Vout
576K 1% + 13K 5%	100K 1%	8.4V	8.3
940K 1% + 4.7K 5%	100K 1%	12.6V	12.59
1.2M 1% + 47K 5%	100K 1%	16.8V	16.26
1.9M 1% + 47K 5%	100K 1%	25.2V	24.1

for - li-battery-dat

= 8.4 / 1.205 - 1 = 5.97, R4 = 5.97 ⅹ R5, if R5 = 100k, R4 = 597k, use 590k
= 12.6 / 1.205 - 1 = 9.46, R4 = 9.46 ⅹ R5, if R5 = 100k, R4 = 946k, use 940k
= 16.8 / 1.205 - 1 = 12.93, R4 = 12.93 ⅹ R5, if R5 = 100k, R4 = 1293k, use 1.2M + 100k in series
= 25.2 / 1.205 - 1 = 19.9, R4 = 19.9 ⅹ R5, if R5 = 100k, R4 = 1990k, use 2M

CN3722

Vbat = 2.416 × (1 + R7 / R6)

where R7 = 14K

Battery Type	Vfb (kΩ)	Output Voltage (V)
LIFEPO4	28.7	3.6
LIFEPO4	7.5	7.2
LIFEPO4	4.02	10.8
Li+	19.1	4.2
Li+	5.76	8.4
Li+	3.3	12.6