IPhone Charging Circuit Diagnostics Guide

IPhone Charging Circuit Diagnostics Guide
Type
Device(s)	iPhone 7, iPhone 7 Plus
Difficulty

Description

iPhones that do not charge, charge intermittently, or only charge wirelessly often suffer from faults in the USB input, USB controller (Tristar / Hydra / Kraken), or charging IC power conversion stages.

This guide outlines a systematic voltage-based diagnostic approach to identify where charging fails.

Supported Models / USB Controller Generations

Tristar Models

• Expected voltages:
  • PP_5V0_USB = 5 V
  • PP_TRISTAR_PIN = 5 V

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Hydra Models (up to iPhone 11 series)

• Expected voltage:
  • PP_VBUS1_E75 = 5 V

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Kraken Models (iPhone 12 series to 14 Series)

• Expected voltage:
  • PP_VBUS1_E75 = 5 V

Diagnostic Steps

1. Check for 5 V Before the Charging IC

• Measure 5 V on the capacitor before the charging IC
• This confirms:
  • Charger is supplying power
  • Port and cable are delivering voltage

❌ No 5 V here = USB input / controller issue

✅ 5 V present = proceed to next step

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2. Understand USB Verification Logic

• The charging IC does NOT know if the cable is good
• Cable validation is handled by the USB controller (Tristar / Hydra / Kraken)

If the USB IC cannot verify the cable:

• The device will not charge via cable
• Wireless charging may still work

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3. Check USB Verification Line

If 5 V is missing at the USB controller, check:

• PP_VAR_USB_RVP_TIGRIS_R (also referred to as PP_VAR_USB_RVP)

This line is required for USB cable validation.

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4. Check the 10 Ω RVP Resistor

Applicable to:

• iPhone 8 / X
• iPhone 13 / 14 / 15

Procedure:

• Locate the 10 Ω resistor on the VAR_USB_RVP line
• Measure voltage on both pads
• Both sides should show ~5 V

❌ Voltage on one side only = open resistor or downstream fault

❌ No voltage on both sides = upstream USB IC issue

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5. Check PWR_GATE_EN_VBUS_1_VALID

• Measure voltage at the PWR_GATE_EN_VBUS_1_VALID test point

Expected result:

• 3.7 V – 5 V (any voltage above 0 V indicates the USB IC is functioning)

Interpretation:

• ✅ Voltage present → USB IC is working
• ❌ 0 V → USB IC is faulty or not powered

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6. Wireless Charging Reference

• Wireless charging does NOT require USB verification
• If wireless charging works but cable charging does not:
  • USB controller / RVP path is likely at fault
  • Charging IC may still be functional

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7. Charging IC Power Conversion

• Charging IC buck-converts 5 V → ~3.7 V
• This voltage is required for the battery to begin charging

If 5 V is present but battery does not charge:

• Suspect charging IC or its output stage

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8. Check CHG_BOOT Line (Diode Mode)

• Locate the capacitor on CHG_BOOT
• Measure in diode mode

Expected readings:

• ❌ Same diode reading on both sides = fault
• From Tigris IC side → ~ 9 V
• From CHG_LX side → ~ 4 V

iPhone USB IC Compatibility Table

USB IC Part Number	iPhone Model
NXP 1610A2	iPhone 6, iPhone 6+
NXP 1610A3	iPhone 6s, iPhone 6s Plus, iPhone SE (1st Gen)
NXP 1610A3B	iPhone 7, iPhone 7 Plus,
NXP 1612A1	iPhone 8, iPhone 8 Plus, iPhone X, iPhone XR, iPhone XS, iPhone XS Max, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone SE (2nd Gen)
NXP 1614A1	iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max
NXP 1616A0	iPhone 13, iPhone 13 mini, iPhone 13 Pro, iPhone 13 Pro Max
NXP 1618A0	iPhone 14, iPhone 14 Plus, iPhone 14 Pro, iPhone 14 Pro Max