====== DCDC ======
===== Load Line =====
{{:wiki:power:dcdc:load_line.jpg}}

| https://doc.inmys.ru/hash/cab9b5440d4a49a3630d42354300008e/load-line_design_for_a_multi-phase_buck_converter_r1.0.pdf |
| https://doc.inmys.ru/hash/a290a7033d13d866a335dc45bea88c7c/Infineon-DCDC_FPGA_load-line-AN-v01_00-EN.pdf |


===== Snubber =====
Snubber - цепочка, компенсирующая паразитные L и C в DCDC.

<WRAP center round tip 60%>
  * Резистор может прилично греться
  * Надо подбирать экспериментально
</WRAP>

Про snubber: 
  * [[https://doc.inmys.ru/open?hash=93ae10ef5c0b31e91241cc1d2fae1e55&fn=buck_snubber_app-e.pdf|ROHM AN]]
  * [[https://doc.inmys.ru/open?hash=b623ee28fa2b904fae0191e87dcebe1e&fn=application_note_en_20180901_AKX00078.pdf|Toshiba AN]]
  * [[https://doc.inmys.ru/open?hash=bec5fbdd996f905c5647a10b63365ccc&fn=AN11160.pdf|Nexperia AN]]
  * [[https://doc.inmys.ru/open?hash=e5a7b0c35777c5f6d971cae57e78eea0&fn=0652.RC%20Snubber.pdf|TI AN]]
  * [[https://doc.inmys.ru/open?hash=e0b56efd0548f6a6fee751e58e5b6e92&fn=Infineon-MOSFET_OptiMOS_simple_design_techniques_for_optimizing_synchronous_rectification-ApplicationNotes-v01_00-EN.pdf|Infineon AN]]

Snubber:\\
{{ :wiki:power:dcdc:snubber_ckt.png?320&direct }}

Пример без snubber:\\
{{ :wiki:power:dcdc:wo_snubber_example.jpg?320&direct }}

Пример после настройки Snubber:\\
{{ :wiki:power:dcdc:w_snubber_example.jpg?320&direct }}

===== MOSFET Self-Turn-On Phenomenon =====
Эффект произвольного включения верхнего транзистора.

Про эффект:
  * [[https://doc.inmys.ru/open?hash=5f1ddf834dcee4535881e87183382b66&fn=application_note_en_20180726_AKX00074.pdf|Toshiba AN]]

**Из app note toshiba:**\\
Selecting MOSFETs with a **high Vth** and a **low Cgd** is of primary importance.

**Из даташита ISL6625A:**\\
Should the driver have insufficient bias voltage applied, its
outputs are floating. If the input bus is energized at a high dV/dt
rate while the driver outputs are floating, due to self-coupling via
the internal CGD of the MOSFET, the gate of the upper MOSFET
could momentarily rise up to a level greater than the threshold
voltage of the device, potentially turning on the upper switch.
Therefore, if such a situation could conceivably be encountered,
it is a common practice to place a resistor (RUGPH) across the
gate and source of the upper MOSFET to suppress the Miller
coupling effect. The value of the resistor depends mainly on the
input voltage’s rate of rise, the CGD/CGS ratio, as well as the
gate-source threshold of the upper MOSFET. A higher dV/dt, a
lower CDS/CGS ratio, and a lower gate-source threshold upper
FET will require a smaller resistor to diminish the effect of the
internal capacitive coupling. For most applications, the
integrated 20kΩ resistor is sufficient, not affecting normal
performance and efficiency.

{{:wiki:power:dcdc:self_turn_on_eq.jpg}}

The coupling effect can be roughly estimated with Equation 5,
which assumes a fixed linear input ramp and neglects the
clamping effect of the body diode of the upper drive and the
bootstrap capacitor. Other parasitic components such as lead
inductances and PCB capacitances are also not taken into
account. Figure 6 provides a visual reference for this
phenomenon and its potential solution.

{{:wiki:power:dcdc:miller_coupling_sch.jpg}}

===== NTC temp measurement and treshold =====
На примере ISL95866.

Кусок схемы:\\
{{:wiki:power:dcdc:isl95866_ntc_sch.jpg?480}}


Характеристика термистора [[|NCP18WM474E03RB]] (2-я кривая):\\
{{:wiki:power:dcdc:ncp18wm474e03rb_r_temp.jpg?480}}

Внутри контроллера:\\
{{:wiki:power:dcdc:isl85966_ntc_cir_int.jpg?480}}

Пороги контроллера:\\
{{:wiki:power:dcdc:isl95866_tresholds_ntc.jpg?800}}

R|| = 1/(1/18k + 1/Rntc)

U = 10uA * (13k3 + R||)

^ Температура ^ Сопротивление термистора ^ Напряжение на входе при токе 10uA ^
| 25 град     | 475k                     |           306mV                   |
| 75 град     | 54k                      |           268mV                   |
| 90 град     | 25k                      |           237mV                   |

Видно, что при 90 град. защита ещё не сработает.

Если необходимо, чтобы при 90 град. срабатывла защита, то R451 можно заменить на 10K. Тогда получается:\\
^ Температура ^ Сопротивление термистора ^ Напряжение на входе при токе 10uA ^
| 25 град     | 475k                     |           273mV                   |
| 75 град     | 54k                      |           235mV                   |
| 90 град     | 25k                      |           204mV                   |

Т.е. при достижении 90 град. будет вырабатываться сигнал VR_HOT. При остывании до 75 град. VR_HOT будет сбрасываться.

<WRAP center round important 60%>
Надо всё это проверить.
</WRAP>