ESP32-P4 vs P4X: what chip revision v3.x changes on your PCB

The ESP32-P4 datasheet (pre-release v0.7) now lists two parts, ESP32-P4NRW16X and ESP32-P4NRW32X, with 16 MB and 32 MB of PSRAM in the package, and gives both as chip revision v3.x. Espressif’s chip revision v3.x user guide names the same two as its related products. The development boards follow: Espressif’s documentation gives one difference between the ESP32-P4X-Function-EV-Board and the ESP32-P4-Function-EV-Board, the main chip, which is chip revision v3.1 or later on the P4X board. The ESP32-P4X-EYE and ESP32-P4X-C5-Function-EV-Board carry the same X.

What the X itself stands for, Espressif does not write down. The datasheet’s nomenclature explains every other letter (N for normal-temperature PSRAM, R for PSRAM, W for 16-line 1.8 V PSRAM, the number for the PSRAM size in MB) and stops there. The same datasheet also says that several chip revisions can be on the market under the same part number. So read the X as “the v3.x part” when you order, and confirm the revision on the chip itself, as shown below.

Revision v3.x is a large change inside the chip: the high-performance RISC-V cores go from 360 MHz to 400 MHz, and for v3.1 Espressif counts more than 50 hardware and register changes, in the ISP, the CPU, memory, the flash and PSRAM interface and the security blocks among others. For a board designer, three of them reach the PCB.

Espressif marks v1.0 and v1.3 “not recommended for new designs” throughout its hardware design guidelines, and the reference schematic for v3.0 and later is the one to start from.

The P4’s high-performance core does not run from your 3.3 V rail. Its four VDD_HP pins take 0.99 to 1.3 V (1.1 V typical) from an external step-down converter, and the chip controls that converter itself through two pins: EN_DCDC (pin 79) switches it on once the firmware starts, and FB_DCDC (pin 78) goes to the converter’s feedback pin. Espressif’s example is a TLV62569 with 4.7 µF in, a 2.2 µH inductor and 22 µF out.

On v1.x, the feedback resistors and capacitor were optional. Espressif’s v1.x schematic shows R1, R2 and C2 as TBD(NC) with a note not to mount them by default, and the guidelines asked designers to keep the pads anyway.

On v3.0 and later, Espressif writes that the feedback resistor and feedback capacitor must be populated: R1 = 499 kΩ from the DC/DC output (ESP_VDD_HP) to FB_DCDC, R2 = 499 kΩ from FB_DCDC to ground, and C2 = 22 pF across R1. With its own TLV62569 values unchanged, that is the whole DC/DC difference. If you use another converter, pick it from Espressif’s verified list (ETA3485, SY8088, RY3420, BL8028, LP3219 or TLV62569), take its input and inductor from its own datasheet, and place it close to the P4, which the reference schematic stresses.

On v1.0 and v1.3, pin 54 of the QFN104 package is NC. From v3.0 it is VDD_HP_1, one of the four high-performance supply pins: VDD_HP_0 is pin 26, VDD_HP_1 pin 54, VDD_HP_2 pin 76 and VDD_HP_3 pin 91. All four take the same ESP_VDD_HP rail.

Espressif’s v3.0 reference schematic feeds pin 54 from ESP_VDD_HP through a 0 Ω resistor (R39) and puts a 0.1 µF capacitor (C39) right at the pin, the same 0.1 µF each VDD_HP pin gets; pin 26 also has the 10 µF bulk capacitor. On a layout, that means a trace or plane connection from the core supply to pin 54 and a decoupling capacitor beside it, at a pin that used to have nothing.

The P4’s high-speed USB 2.0 OTG pins are USB_DM (pin 49) and USB_DP (pin 50). On v1.0 and v1.3, Espressif adds a 1 MΩ pull-down on USB_DP to stop a large transient current on VDD_USBPHY when CHIP_PU is pulled low. In v3.0 and later that is fixed, and Espressif allows the 1 MΩ to stay for design compatibility. Its v3.0 schematic draws it as R41, 1M(NC).

A related v1.x fix also goes away: on v1.0 and v1.3, VDD_USBPHY leaks current in low-power modes and Espressif recommends a MOSFET to switch it off. In v3.0 that is fixed too, and the 0 Ω in series with VDD_USBPHY can stay.

Not without changes. Two of the three are part changes: fit R1, R2 and C2 on the pads Espressif told you to keep, and the 1 MΩ on USB_DP can stay. Pin 54 is the problem. A v1.x layout had no reason to route it, so on most boards the pad connects to nothing, and v3.x needs it on the core supply with a capacitor beside it. That is a layout change: plan a new board revision.

The manufacturing code line in the chip marking gives the revision. From Espressif’s errata, chip revision identification:

In software the revision is in eFuse: the major number in EFUSE_RD_MAC_SPI_SYS_2_REG bits 23, 5 and 4, the minor number in bits 3 to 0. esptool reads it and prints the chip revision when it connects. In Espressif’s vM.X scheme, a change in M means software for the old revision does not run on the new one, which is why v1.x and v3.x need separate builds.

Chip revision v3.x needs ESP-IDF v5.5.3 or later, or v6.0 or later. Those versions add one option to sdkconfig, CONFIG_ESP32P4_SELECTS_REV_LESS_V3: n, the default, builds for v3.x; y builds for v1.x. A project started on an in-between ESP-IDF version may still carry CONFIG_ESP32P4_SELECTS_REV_LESS_V3=y, and then the firmware either fails to download to a v3.x chip or fails to boot after flashing. Set it to n and rebuild.

Espressif is explicit that the two revisions cannot share one firmware image. If your product ships with both, build and track two images.

For the rest of a new v3.x board’s power circuit, these are the numbers from Espressif’s schematic checklist:

The P4 has no radio. A P4 board that needs Wi-Fi or Bluetooth adds a second chip, as Espressif’s P4X-C5 board does with an ESP32-C5-MINI-1 module; for that part of the board, the ESP32 PCB design guide covers the antenna keep-out, power and USB rules.

KiCad 9.0.9’s standard library has symbols for the ESP32-C3, ESP32-S2, ESP32-S3 and the PICO chips, and none for the ESP32-P4, so you will draw your own or bring one in. Build it from the current datasheet, not from a v1.x design:

• Pin 54 is VDD_HP_1 with the power-input pin type. A symbol made for v1.x marks it NC, and KiCad’s electrical rule check says nothing about an unconnected NC pin, so the mistake survives until the board does not boot.
• Give FB_DCDC and EN_DCDC their own nets to the converter’s FB and EN pins. Neither goes to your 3.3 V rail.
• Put R1, R2 and C2 on the schematic with values, not as do-not-populate parts, and keep C39 beside pin 54 in the layout.
• If you keep the 1 MΩ on USB_DP so one layout suits both revisions, mark it do-not-populate for v3.x builds, and check that your bill of materials and position file leave it out.

The two figures above were drawn that way: KiCad’s own TLV62569DBV, resistor, capacitor and inductor symbols, Espressif’s values and reference designators, and KiCad’s DNP flag on the parts Espressif leaves unmounted. If KiCad reports power pins that nothing drives once the P4 symbol is in, the power pin page explains the fix.