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BOM-DAT/capacitor-dat/ESR-capacitor-dat/ESR-capacitor-dat.md
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+
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+# ESR-capacitor-dat.md
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+
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+
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+**ESR** stands for **Equivalent Series Resistance**.
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+A capacitor is not ideal — it behaves like it has a small resistor in series with its capacitance. This resistor is called ESR.
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+
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+---
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+
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+## 1. Definition
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+
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+**ESR capacitor** = a capacitor with **low equivalent series resistance**, designed to supply or absorb high-frequency current spikes efficiently.
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+
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+Mathematically: ESR = Resistive component in series with the capacitor
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+
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+In circuit models: Capacitor → [ Ideal Capacitance C ] — [ ESR ] — [ Inductance ]
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+
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+## 2. Why ESR Matters
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+
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+When a capacitor is used for **power supply smoothing**, such as powering a SIMCom module:
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+
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+- The module draws **high peak current** during transmission bursts (up to ~2A).
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+- The ESR creates a **voltage drop**:
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+
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+ V_drop = I_peak × ESR
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+
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+- High ESR means more drop → poor voltage stability → possible **module reboot**.
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+
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+ I_peak = 2 A
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+ ESR = 0.5 Ω
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+ V_drop = 2 × 0.5 = 1 V drop
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+
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+If VBAT is 4.2 V, a 1 V drop means the module sees 3.2 V → unstable operation.
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+
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+
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+## 3. Low ESR Capacitor
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+
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+A **low ESR capacitor** has:
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+- Very small ESR (often < 0.1 Ω).
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+- Better performance for high-frequency pulses.
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+- Less heat generated under load.
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+
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+### Typical types:
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+| Type | ESR | Application |
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+|--------------------|---------------|-----------------------------------|
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+| Ceramic MLCC | < 0.01 Ω | High frequency decoupling |
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+| Tantalum | 0.1 – 0.5 Ω | Bulk filtering in low-voltage |
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+| Low-ESR Electrolytic | 0.01 – 0.1 Ω | Bulk power supply smoothing |
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+
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+## 4. Application in GSM/4G Modules
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+For GSM/4G power stability:
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+- Use **low ESR capacitors** close to VBAT pin.
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+- Typical combination:
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+
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+ - 470 µF – 1000 µF low ESR electrolytic/tantalum
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+ - 10 µF ceramic MLCC
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+ - 0.1 µF ceramic MLCC
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+
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+## ref
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+
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+- [[capacitor-dat]]
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+
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+- [[PCB-design-dat]]
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BOM-DAT/capacitor-dat/Electrolytic-cap-dat/Electrolytic-cap-dat.md
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+
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+# Electrolytic-cap-dat
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+
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+
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+## electrolyte
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+
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+![](2025-03-14-20-31-28.png)
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BOM-DAT/capacitor-dat/MLCC-dat/MLCC-dat.md
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+
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+# MLCC-dat
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+
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BOM-DAT/capacitor-dat/Tantalum-dat/Tantalum-dat.md
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+
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+# Tantalum-dat
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+
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+
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+
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+## TAJ Series
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+
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+![](2023-10-17-16-19-42.png)
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+
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+
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+
BOM-DAT/capacitor-dat/capacitor-dat.md
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1 1
2 2
# cap-dat
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+- [[ESR-capacitor-dat]] - [[MLCC-dat]] - [[Electrolytic-cap-dat]] - [[tantalum-dat]]
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+
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+
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+
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+
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+## brands
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+
4 11
common brand: Chemi-Con, Vishay, TDK, Pansonic, KEMET, Nichicon
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6 13
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-- [[decoupling-capacitor-dat]]
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+## function
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+
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+- [[capacitor-decoupling-dat]]
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+- [[start-capacitor-dat]] - [[CBB-capacitor-dat]]
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11 21
## Aluminum Electrolytic Capacitors - Radial Leaded
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@@ -65,13 +75,6 @@ Tantium PTH capacitor
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-## TAJ Series
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-
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-![](2023-10-17-16-19-42.png)
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-
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-
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-
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-
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## Specs
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-## electrolyte
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-![](2025-03-14-20-31-28.png)
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-
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-## Functional Capacitors
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-
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-- [[start-capacitor-dat]] - [[CBB-capacitor-dat]]
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98 95
99 96
### DC blocking capacitor
PCB-dat/PCB-design-dat/PCB-design-dat.md
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@@ -3,6 +3,8 @@
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4 4
- [[footprint-dat]] - [[thermal-disppation-dat]] - [[heatsink-dat]] - [[PCB-installation-dat]]
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+- [[PCB-layout-dat]] - [[PCB-trace-dat]]
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+
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7 9
- [[EDA-dat]] - [[EDA-simulation-dat]]
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17 19
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- [[BTB-dat]]
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-- [[PCB-layout-dat]]
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-
22 22
- [[test-point-dat]]
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PCB-dat/PCB-design-dat/PCB-trace-dat.md
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+
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+# PCB-trace-dat
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+
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+- [[differential-signal-dat]]
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+
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+### Quick reference table (External trace, 1 oz copper, ΔT = 10°C):
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+
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+| Current (A) | Trace Width (mil) | Width (mm) |
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+|-------------|---------------------|------------|
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+| 1.0 | ~10 | ~0.25 |
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+| 2.0 | ~20 | ~0.50 |
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+| 3.0 | ~30 | ~0.76 |
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+| 4.0 | ~45 | ~1.14 |
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+
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+
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+## ref
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+
18
+- [[PCB-design-dat]]
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