AT9880

@@ -0,0 +1,77 @@+# AT9880++**ZHONGKEWEI** · GNSS Modules · QFN-40L-EP(5x5)++AT9880 from ZHONGKEWEI, in a QFN-40L-EP(5x5). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | RF1 | input | L1-band RF signal input (1561.098 MHz min / 1575.42 MHz typ / 1602 MHz max). DC voltage must not exceed 0.8V; AC-couple with a series capacitor if the external LNA output carries DC. |+| 2 | GND | power_in | Ground. |+| 3 | VDD_ANA | power_out | Analog LDO output. Bypass with 1uF decoupling capacitor close to the pin. |+| 4 | VX_OUT | power_out | TCXO supply output (1.8V typ). Bypass with 1uF decoupling capacitor; feeds the external TCXO EN/VCC. |+| 5 | XREF | input | Reference clock input from external 26 MHz TCXO. Accepts clipped-sine drive 0.5-1.5 Vpp. |+| 6 | TST_RF | unconnected | Factory RF test port. Leave floating in normal application. |+| 7 | VDD_BK | power_out | Backup-domain LDO output. Bypass with 1uF decoupling capacitor close to the pin. |+| 8 | VBAT | power_in | Backup power input for the RTC/backup-RAM domain (1.4-3.6V, 3.3V typ). Keeps RTC time and backup RAM alive when the main supply is removed to enable warm/hot start. |+| 9 | VDD_IO | power_in | Digital I/O supply input (2.7-3.6V, 3.3V typ). Also feeds the POR and antenna-detect circuits. |+| 10 | ANT_BIAS | power_out | Active-antenna bias/feed with integrated current sensing for antenna open/short detection and short-circuit protection (short-protection trip 45-65 mA, typ 50 mA). |+| 11 | RTC_O | output | 32.768 kHz RTC oscillator output. Connect the 32.768 kHz crystal (12.5 pF CL, ≤80 kΩ ESR) between RTC_O and RTC_I. |+| 12 | RTC_I | input | 32.768 kHz RTC oscillator input. Other terminal of the RTC crystal. |+| 13 | GPIO2/TXD1 | bidirectional | UART1 TXD (default) / general-purpose digital I/O. |+| 14 | GPIO3/RXD1 | bidirectional | UART1 RXD (default) / general-purpose digital I/O. |+| 15 | Reserved | unconnected | Reserved. Leave floating when unused. |+| 16 | Reserved | unconnected | Reserved. Leave floating when unused. |+| 17 | nRST | input | Active-low external reset input, internal pull-up. Reset threshold VDD_IO ≈1.65V; internal nRESET released ~160 ms after nRST rises. Leave floating if unused. |+| 18 | GPIO1/RXD0 | bidirectional | UART0 RXD (default communication port) / general-purpose digital I/O. |+| 19 | GPIO0/TXD0 | bidirectional | UART0 TXD (default positioning output) / general-purpose digital I/O. |+| 20 | GPIO27 | bidirectional | General-purpose digital I/O (Vih ≥ 0.8·VDD_IO, Vil ≤ 0.2·VDD_IO, Voh ≥ VDD_IO−0.4V, Vol ≤ 0.4V; internal 80 kΩ pull-up/pull-down programmable). |+| 21 | DX_IN | power_in | Internal DCDC converter input (typically tied to 3.3V main supply). Decouple with a 2.2uF cap; the DCDC steps 3.3V down for the internal core LDO. |+| 22 | DX_OUT | power_out | Internal DCDC switching-node/output. Connect the DCDC inductor (4.7uH) and 10uF output cap; the resulting rail feeds VCORE. |+| 23 | VCORE | power_in | Core LDO input (1.2V min, 3.6V max). Normally sourced from DX_OUT via the DCDC, but may be driven from an external supply. |+| 24 | VDD_BB | power_out | Digital core LDO output (1.0V typ). Bypass with 2.2uF decoupling capacitor close to the pin. |+| 25 | GPIO22 | bidirectional | General-purpose digital I/O; default function is 1PPS timing output. |+| 26 | Reserved | unconnected | Reserved. Leave floating when unused. |+| 27 | Reserved | unconnected | Reserved. Leave floating when unused. |+| 28 | Reserved | unconnected | Factory test port. Leave floating when unused. |+| 29 | ON_OFF | input | Shutdown/wake control input; internal pull-up. Drive low to enter sleep mode (~50 uA); leave floating if unused. |+| 30 | GPIO4 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 31 | GPIO5 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 32 | GPIO8 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 33 | GPIO7 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 34 | GPIO6 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 35 | GPIO10 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 36 | GPIO9 | bidirectional | General-purpose digital I/O. Leave floating when unused. |+| 37 | DVDD | power_out | PLL LDO output. Bypass with 1uF decoupling capacitor close to the pin. |+| 38 | GND | power_in | Ground; also acts as RF isolation pin between RF1 and RF2 - tie directly to PCB ground plane with multiple vias. |+| 39 | RF2 | input | L5-band RF signal input (1176.45 MHz). DC voltage must not exceed 0.8V; AC-couple with a series capacitor if the external LNA output carries DC. |+| 40 | GND | power_in | Ground. |+| EP | GND | power_in | Exposed thermal pad on package underside. Must be soldered directly to the PCB ground plane with a full via array for thermal and electrical grounding. |++## Key specifications++| Parameter | Value |+|---|---|+| Manufacturer | ZHONGKEWEI |+| Package | QFN-40L-EP(5x5) |+| Category | IoT/Communication Modules |+| Pins | 41 |++## CAD (KiCad official)++- Symbol: `AT9880`+- Footprint: `Package_DFN_QFN:QFN-40-1EP_5x5mm_P0.4mm_EP3.6x3.6mm`+- 3D model: QFN-40L-EP(5x5) (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [ZHONGKEWEI datasheet](docs/at9880-datasheet.pdf) (16 pp, sha256 `97d93eb7c809245b`, retrieved 2026-08-17, tier: lcsc)+- **Datasheet language:** Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/at9880-datasheet.pdf)

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