resistor-feedback-dat
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 | 5.2V | 13.3K | 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 |
FB = VBAT＝1.205×(1＋R1／R2)
电池端对应的的电压为： VBAT＝1.205×(1＋R1／R2)
parallel 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
li-battery
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 |