Understanding Mini-PCIe

Mini PCIe is a scaled down version of PCIe which uses 1 lane for connecting to an external card. This interface mainly used in notebooks, tablets, laptops is used for connecting Wi-Fi, Bluetooth, Cellular broadband, Ethernet cards to the processor.

The following figures show the Mini PCIe connectors and cards available in the market:

The following are the signals in mini PCIe connector:

• PCIe x1
• Reference Clock
• USB2.0
• SMBus
• LED's for diagnosis and signalling
• SIM card connectivity
• 1.5V/3.3V power (1 pin for 3.3 V Aux, 2 pins for +3.3 V main, 3 pins for +1.5 V main, 12 GND pins)
• Some slots for future PCIe lane expansion

What may not be possible with Mini PCIe slot?

• Graphics cards 
• Video cards

This is because with the existing lanes in Mini PCIe band-width will not be enough for handling graphics content.

Mini PCIe Connector specifications:

• 52-pin edge connector used
• Staggered with 2 rows
• 0.8mm pitch
• Dimensions: 30 x 50.95 mm

Other important considerations in Mini PCIe:

• Mini PCIe uses a differential clock of 100 MHz
• Wake mechanism (in band) which helps module to be in stand-by mode during idle states
• With the 52-pin staggered edge connector used, angled insertion and removal of add-in cards is done
• Some add-in card connectivity can be screwed for mechanical support
• Maximum power supported is 2.3 W
• With +3.3 V power lane, peak current supported is 1 A 
• With +1.5 V power lane, peak current supported is 1.5 V
• +3.3 V is mainly used for I/O requirements, +1.5 V is only to avoid any on-board regulation
• LED's used in Mini PCIe must be 9 mA sink capable
• If you have Mini PCIe card and on board PCIe connectivity is only available, then, adapters are available for use in the market

Targeted applications for Mini PCIe:

• Wireless Personal Area network (BT, UWB cards)
• Local Area network cards (10/100/1G/10G cards)
• Wireless Local Area network (802.11a/b/g cards)
• Wireless Area Network (xDSL, Cable modem)
• Wireless Wide Area Network (GSM/GPRS/UMTS/CDMA cards)