LimeSDR-Mini v1.1 hardware description

LimeSDR-Mini Board Key Features

The LimeSDR-Mini is low-cost software defined radio board. LimeSDR-Mini development board provides a hardware platform for developing and prototyping high-performance and logic-intensive digital and RF designs using Intel’s MAX 10 FPGA and Lime Microsystems transceiver.

Figure 1. LimeSDR-Mini v1.1

LimeSDR-Mini board features:

• USB 3.0 controller: FTDI FT601
• FPGA: Intel MAX 10 (10M16SAU169C8G 169-UBGA)
  • 169-pin FBGA package
  • 16 K LE
  • 549 Kb M9K Memory
  • 2368 Kb User Flash Memory
  • 1x fractional phase locked loops (PLLs)
  • 45x 18x18-bit multipliers
  • 130x general purpose input/output (GPIO)
  • Single supply
  • Flash feature
  • FPGA configuration via JTAG
• RF transceiver: Lime Microsystems LMS7002M
• EEPROM Memory: 2x 128Kb EEPROMs for LMS MCU firmware and FPGA data
• FLASH Memory: 4Mb Flash memory for FPGA data
• Temperature sensor (unpopulated)
• General user inputs/outputs:
  • 1x Dual colour (RG) LED
  • 8x + 2x FPGA GPIO pinheader (3.3V)
• Connections:
  • USB3.0 (type A) plug
  • Coaxial RF (SMA female) connectors
  • FPGA GPIO headers (unpopulated)
  • FPGA JTAG connector (unpopulated)
  • FAN (5V or 3.3V) connector
• Clock system:
  • 40.00MHz onboard VCTCXO
  • Possibility to tune VCTCXO by onboard DAC
  • Reference clock input and output connectors (U.FL)
• Board size: 69mm x 31.4mm

For more information on the following topics, refer to the respective documents:

• FTDI FT601 USB 3.0 to FIFO Bridge datasheet [link]
• MAX 10 FPGA device family, refer to MAX 10 Device Handbook [link]
• LMS7002M transceiver resources [link]

Board Overview

This section contains component location description on the board. LimeSDR-Mini board picture with highlighted connectors and main components is presented in Figure 2 and Figure 3.

Figure 2. LimeSDR-Mini v1.1 board top connectors and main components

Figure 3. LimeSDR-Mini v1.1 board bottom connectors and main components

Board components description listed in the Table 1.

Table 1. Board components

Featured Devices
Board reference	Type	Description
IC1	FPRF	Field programmable RF transceiver, LMS7002M
IC5	FPGA	Intel MAX 10 (10M16SAU169C8G 169-UBGA)
IC6	USB 3.0 microcontroller	FTDI USB 3.0 to FIFO interface bridge chip FT601
Miscellaneous devices onboard
IC8	IC	Temperature sensor, LM75
Configuration, Status and Setup Components
J3	JTAG chain connector	FPGA programming pin header on the board edge for Altera USB-Blaster download cable, 0.1” pitch
J4	JTAG chain connector	FPGA programming pin header for Altera USB-Blaster download cable, 0.05” pitch
LED1 or LED2	LED1 or LED2c	USB3.0 microcontroller (IC13) boot configuration (PMODE0[2:0]) resistors. Default mode: SPI boot, On Failure - USB Boot
General User Input/Output
J5	Pin header	8x FPGA GPIOs, 3.3V, 0.05” pitch
J6	Pin header	2x FPGA GPIOs on the board edge, 3.3V, 0.1” pitch
J10	Pin header	5V (3.3V voltage can be chosen by resistors) fan connection pin headers, 0.1” pitch
Memory Devices
IC2	IC	I²C EEPROM Memory 128Kb (16K x 8), connected to RF transceiver I2C bus
IC10	IC	I²C EEPROM Memory 128Kb (16K x 8), connected to FPGA I2C bus
IC11	IC11	Quad SPI Flash Memory 4Mb (512K x 8), connected to FPGA SPI
Communication Ports
J7	USB3.0 connector	USB3.0 connector
Clock Circuitry
XO1	VCTCXO	40.00 MHz Voltage Controlled Temperature Compensated Crystal Oscillatorc
IC9	IC	DAC for TCXO (XT4) frequency tuning
IC7	IC7	Clock buffer
J8	U.FL connector	Reference clock input
J9	U.FL connector	Reference clock output
Reference clock output
IC12	IC	Switching regulator (1.8V)
IC13	IC	Switching regulator (3.3V)
IC14	IC	Linear regulator (2.5V)

RF Frequency Range

LimeSDR-Mini board covers RF frequency range from 10MHz up to 3.5GHz. There are different matching networks connected to the RF transceiver RF inputs and outputs (antennas):

• Use TX1_1 RF output for 2GHz - 3.5GHz frequency range
• Use TX1_2 RF output for 10MHz - 2GHz frequency range
• Use RX1_H RF input for 2GHz - 3.5GHz frequency range
• Use RX1_W RF input for 10MHz - 2GHz frequency range

LimeSDR-Mini Board Architecture

The heart of the LimeSDR-Mini board is Intel MAX 10 (10M16SAU169C8G 169-UBGA) FPGA. It’s main function is to transfer digital data between the PC through a USB3.0 connector. The block diagram for LimeSDR-Mini board is presented in the Figure 4.

Figure 4. LimeSDR-Mini Development Board Block Diagram

LMS7002M Based Connectivity

The interface and control signals are described below:

• Digital Interface Signals: LMS7002 is using data bus LMS_DIQ1_D[11:0] and LMS_DIQ2_D[11:0], LMS_ENABLE_IQSEL1 and LMS_ENABLE_IQSEL2, LMS_FCLK1 and LMS_FCLK2, LMS_MCLK1 and LMS_MCLK2 signals to transfer data to/from FPGA. Indexes 1 and 2 indicate transceiver digital data PORT-1 or PORT-2. Any of these ports can be used to transmit or receive data. By default PORT-1 is selected as transmit port and PORT-2 is selected as receiver port. The FCLK# is input clock and MCLK# is output clock for LMS7002M transceiver. TXNRX signals sets ports directions. For LMS7002M interface timing details refer to LMS7002M transceiver datasheet page 12-13. [link].

• LMS Control Signals: these signals are used for optional functionality:
  • LMS_RXEN, LMS_TXEN – receiver and transmitter enable/disable signals connected to FPGA Bank 8 (VDIO_LMS_FPGA; 2.5V).
  • LMS_RESET – LMS7002M reset connected to FPGA Bank 7 (VDIO_LMS_FPGA; 2.5V).

• SPI Interface: LMS7002M transceiver is configured via 4-wire SPI interface; FPGA_SPI_SCLK, FPGA_SPI_MOSI, FPGA_SPI_MISO, FPGA_SPI_LMS_SS. The SPI interface controlled from FPGA Bank 2 (VDIO_LMS_FPGA; 2.5V).

• LMS I2C Interface: can be used for LMS EEPROM content modifying or for debug purposes. The signals LMS_I2C_SCL, LMS_I2C_DATA connected to FPGA Bank 2 (VDIO_LMS_FPGA; 2.5V).

Table 2. RF transceiver (LMS7002) digital interface pins

Chip pin (IC1)	Chip reference (IC1)	Schematic signal name	FPGA pin	FPGA I/O standard	Comment
E5	xoscin_tx	TxPLL_CLK	-	1.8V	Connected to 40.00 MHz clock
AB34	MCLK1	LMS_MCLK1	G5	2.5V
AA33	FCLK1	LMS_FCLK1	L3	2.5V
V32	TXNRX1	LMS_TXNRX1	J8	2.5V
U29	TXEN	LMS_TXEN	K6	2.5V
1Y32	ENABLE_IQSEL1	LMS_ENABLE_IQSEL1	M8	2.5V
AG31	DIQ1_D0	LMS_DIQ1_D0	M12	2.5V
AF30	DIQ1_D1	LMS_DIQ1_D1	N12	2.5V
AF34	DIQ1_D2	LMS_DIQ1_D2	N10	2.5V
AE31	DIQ1_D3	LMS_DIQ1_D3	L10	2.5V
AD30	DIQ1_D4	LMS_DIQ1_D4	M10	2.5V
AC29	DIQ1_D5	LMS_DIQ1_D5	M13	2.5V
AE33	DIQ1_D6	LMS_DIQ1_D6	N9	2.5V
AD32	DIQ1_D7	LMS_DIQ1_D7	N8	2.5V
AC31	DIQ1_D8	LMS_DIQ1_D8	M7	2.5V
AC33	DIQ1_D9	LMS_DIQ1_D9	N7	2.5V
AB30	DIQ1_D10	LMS_DIQ1_D10	M9	2.5V
AB32	DIQ1_D11	LMS_DIQ1_D11	N6	2.5V
AM24	xoscin_rx	RxPLL_CLK	-	1.8V	Connected to 40.00 MHz clock
P34	MCLK2	LMS_MCLK2	H4	2.5V
R29	FCLK2	LMS_FCLK2	M3	2.5V
U31	TXNRX2	LMS_TXNRX2	H5	2.5V
V34	RXEN	LMS_RXEN	M11	2.5V
R33	ENABLE_IQSEL2	LMS_ENABLE_IQSEL2	N3	2.5V
H30	DIQ2_D0	LMS_DIQ2_D0	M2	2.5V
J31	DIQ2_D1	LMS_DIQ2_D1	M4	2.5V
K30	DIQ2_D2	LMS_DIQ2_D2	M1	2.5V
K32	DIQ2_D3	LMS_DIQ2_D3	J1	2.5V
L31	DIQ2_D4	LMS_DIQ2_D4	N2	2.5V
K34	DIQ2_D5	LMS_DIQ2_D5	K1	2.5V
M30	DIQ2_D6	LMS_DIQ2_D6	L2	2.5V
M32	DIQ2_D7	LMS_DIQ2_D7	J2	2.5V
N31	DIQ2_D8	LMS_DIQ2_D8	N4	2.5V
N33	DIQ2_D9	LMS_DIQ2_D9	K2	2.5V
P30	DIQ2_D10	LMS_DIQ2_D10	L5	2.5V
P32	DIQ2_D11	LMS_DIQ2_D11	L4	2.5V
U33	CORE_LDO_EN	LMS_CORE_LDO_EN	N11	2.5V
E27	RESET	LMS_RESET	L1	2.5V
D28	SEN	FPGA_SPI_LMS_SS	J5	2.5V	SPI interface
C29	SCLK	FPGA_SPI_SCLK	K5	2.5V	SPI interface
F30	SDIO	FPGA_SPI_MOSI	J7	2.5V	SPI interface
F28	SDO	FPGA_SPI_MISO	J6	2.5V	SPI interface
D26	SDA	LMS_I2C_SDA	N5	2.5V	Connected to EEPROM
C27	SCL	LMS_I2C_SCL	M5	2.5V	Connected to EEPROM

USB 3.0 controller

Software controls LimeSDR-Mini board via the USB3 microcontroller (FTDI USB 3.0 to FIFO interface bridge chip FT601 [link]). The controller signals description showed below:

• FT_D[31:0] – FTDI 32-bit data interface is connected to FPGA.
• FT_TXEn, FT_RXFn, FT_SIWUn, FT_WRn, FT_RDn, FT_OEn, FT_BE[3:0] – FTDI interface control signals.
• FT_CLK – FTDI interface clock. Clock from FTDI is fed to FPGA.

In the table below are listed USB3.0 controller (FTDI) pins, schematic signal name, FPGA interconnections and I/O standard.

Table 3. USB3 controller (FTDI) pins

Chip pin (IC6)	Chip reference (IC6)	Schematic signal name	FPGA pin	I/O standard	I/O standard
40	DATA_0	FT_D0	A2	3.3V
41	DATA_1	FT_D1	B6	3.3V
42	DATA_2	FT_D2	B3	3.3V
43	DATA_3	FT_D3	B5	3.3V
44	DATA_4	FT_D4	A3	3.3V
45	DATA_5	FT_D5	B4	3.3V
46	DATA_6	FT_D6	E6	3.3V
47	DATA_7	FT_D7	A4	3.3V
50	DATA_8	FT_D8	B12	3.3V
51	DATA_9	FT_D9	H8	3.3V
52	DATA_10	FT_D10	E9	3.3V
53	DATA_11	FT_D11	B2	3.3V
54	DATA_12	FT_D12	D9	3.3V
55	DATA_13	FT_D13	J9	3.3V
56	DATA_14	FT_D14	A9	3.3V
57	DATA_15	FT_D15	H9	3.3V
60	DATA_16	FT_D16	A7	3.3V
61	DATA_17	FT_D17	F8	3.3V
62	DATA_18	FT_D18	A6	3.3V
63	DATA_19	FT_D19	E10	3.3V
64	DATA_20	FT_D20	A5	3.3V
65	DATA_21	FT_D21	F9	3.3V
66	DATA_22	FT_D22	E8	3.3V
67	DATA_23	FT_D23	A8	3.3V
69	DATA_24	FT_D24	K11	3.3V
70	DATA_25	FT_D25	K12	3.3V
71	DATA_26	FT_D26	J12	3.3V
72	DATA_27	FT_D27	G12	3.3V
73	DATA_28	FT_D28	L13	3.3V
74	DATA_29	FT_D29	G13	3.3V
75	DATA_30	FT_D30	J13	3.3V
76	DATA_31	FT_D31	H13	3.3V
58	CLK	FT_CLK	G9	3.3V
4	BE_0	FT_BE0	B11	3.3V
5	BE_1	FT_BE1	C12	3.3V
6	BE_2	FT_BE2	A12	3.3V
7	BE_3	FT_BE3	B13	3.3V
8	TXE_N	FT_TXEn	C13	3.3V
9	RXF_N	FT_RXFn	A12	3.3V
10	SIWU_N	FT_SIWUn	-	3.3V	10k pull up
11	WR_N	FT_WRn	E12	3.3V
12	RD_N	FT_RDn	D12	3.3V
13	OE_N	FT_OEn	F12	3.3V
15	RESET_N	FT_RESETn	L12	3.3V
16	WAKEP_N	FT_WAKEUPn	H10	3.3V

Indication LEDs

LimeSDR-Mini board comes with one dual colour (red and green (RG)) indication LED. This LEDs can be soldered on the top (LED1) or on the bottom (LED2). By default, LED1 is populated and LED2 is unpopulated.

Figure 5. LimeSDR-Mini indication LEDs

LEDs are connected to FPGA to the same lines and their function can be changed.

Low speed interfaces

LimeSDR-Mini board low speed interfaces are presented in Figure 6. The latter block diagrams depict the main ICs, corresponding IC pin numbers, data buses and serial protocol addresses.

Figure 6. Low speed interfaces block diagram

There are several SPI interfaces with their slave devices:

• FPGA_SPI: this SPI interface are connected to FPGA and slave devices can be accessed by transferring data to internal FPGA NIOS CPU. This bus has these slave devices RFIC (IC1) and DAC (IC9).

• FPGA_QSPI: this SPI interface is connected to Quad SPI flash memory (IC11).

• Internal FPGA SPI module: FPGA has its own SPI module and can be controlled as regular SPI device. By using FPGA SPI it is possible to control FPGA modes etc.

• FPGA_I2C: used to control external clock temperature sensor and EEPROM on LimeSDR-Mini board.

In the tables below are listed FPGA_SPI pins, schematic signal names, FPGA interconnections and I/O standards.

Table 4. FPGA_SPI interface pins

Schematic signal name	FPGA pin	I/O standard	Comment
FPGA_SPI_SCLK	K5	2.5V (3.3V)	Serial Clock (FPGA output)
FPGA_SPI_MOSI	J7	2.5V (3.3V)	Data (FPGA output)
FPGA_SPI_MISO	J6	2.5V (3.3V)	Data (FPGA input)
FPGA_SPI_LMS_SS	J5	2.5V (3.3V)	IC1 (LMS7002) SPI slave select (FPGA output)
FPGA_SPI_DAC_SS	K8	2.5V (3.3V)	IC9 SPI slave select (FPGA output)

In the tables below are listed FPGA_QSPI pins, schematic signal names, FPGA interconnections and I/O standards.

Table 5. FPGA_QSPI interface pins

Schematic signal name	FPGA pin	I/O standard	Comment
FPGA_QSPI_SCLK	F1	1.8V	Serial Clock (FPGA output)
FPGA_QSPI_IO0	D1	1.8V
FPGA_QSPI_IO1	C1	1.8V
FPGA_QSPI_IO2	B1	1.8V
FPGA_QSPI_FLASH_SS	E1	1.8V	FPGA_QSPI_FLASH_SS

In the tables below are listed FPGA_I2C interface slave devices and their other information.

Table 6. FPGA_I2C interface pins

I2C slave device	Slave device	I2C address	I/O standard	Comment
IC8	Temperature sensor	1 0 0 1 0 0 0 RW	3.3V	LM75
IC10	EEPROM	1 0 1 0 0 0 0 RW	3.3V	M24128

8 GPIOs from FPGA are connected to 10 pin 0.05” header. Additional 2 pins are dedicated for power. Another 2 GPIOs are connected to 5 header on the board edge. In the tables below are listed FPGA_GPIO (J5) and FPGA_EGPIO (J6) information.

Table 7. FPGA GPIO connector (J5) pins

Connector pin	Schematic signal name	FPGA pin	I/O standard	Comment
1	FPGA_GPIO0	A11	3.3V
2	FPGA_GPIO1	B10	3.3V
3	FPGA_GPIO2	C10	3.3V
4	FPGA_GPIO3	D11	3.3V
5	FPGA_GPIO4	E13	3.3V
6	FPGA_GPIO5	F13	3.3V
7	FPGA_GPIO6	F10	3.3V
8	FPGA_GPIO7	G10	3.3V
9	GND	-		Ground pin
10		-		Selectable power net (3.3V or 5V). Default 3.3V

Table 8. FPGA EGPIO connector (J5) pins

Connector pin	Schematic signal name	FPGA pin	I/O standard	Comment
1	GND			Ground pin
2	FPGA_EGPIO0	B7	3.3V
3	FPGA_EGPIO1	D6	3.3V
4	VCC3P3		3.3V	Power net (3.3V)
5	VCC1P8		1.8V	Power net (1.8V)

Board Temperature Control

LimeSDR-Mini has integrated temperature sensor which controls FAN to keep board in operating temperature range. FAN must be connected to J10 (0.1” pitch) connector. FAN control voltage is 5V, but it can be changed to 3.3V by resistors. Fan will be turned on if board will heat up to 55°C and FAN will be turned off if board will cool down to 45°C. By default temperature sensor is unpopulated and FAN is always on.

Figure 7. FAN control temperature hysteresis

Clock Distribution

LimeSDR-Mini board clock distribution block diagram is presented in Figure 8. LimeSDR-Mini board has onboard 40.00 MHz VCTCXO that is reference clock for LMS and FPGA PLLs.

Figure 8. LimeSDR-Mini board clock distribution block diagram

VCTCXO frequency can be tuned by using DAC (IC8). Buffered VCTCXO clock is connected to RF transceiver, FPGA. Buffered VCTCXO clock is also connected to connector J9 (REF_CLK_OUT) and can be fed to external hardware for synchronisation. VCTCXO can be disconnected from clock buffer input (remove R59 and solder R62) and external reference clock can be supplied from connector J8 (REF_CLK_IN).

Table 9. LimeSDR-Mini clock pins

Source	Schematic net name	I/O standard	FPGA pin	Description
External	REF_CLK_IN			External reference clock input
Board	Board	2.5V (3.3V)		Buffered reference clock output
Clock buffer (IC7)	LMK_CLK	2.5V (3.3V)	H6	Buffered reference clock output
RF transceiver (IC1)	RxPLL_CLK	2.5V (3.3V)		Buffered reference clock output
	TxPLL_CLK	2.5V (3.3V)		Buffered reference clock output
	LMS_MCLK1	2.5V (3.3V)	G5
	LMS_FCLK1	2.5V (3.3V)	L3
	LMS_MCLK2	2.5V (3.3V)	H4
	LMS_FCLK2	2.5V (3.3V)	M3
USB3.0 controller	FT_CLK	3.3V	G9	100 MHz

External clock notes. External clock capabilities on LimeSDR-Mini board are defined by LMK00105 clock buffer specification. User must ensure voltage levels are in the range of LMK00105 capabilities. Ideally, a phase detector circuitry should be used to synchronize on board TCXO to the external clock but there simply is no space on LimeSDR-Mini for this functionality. Hence decision was made just to provide an input to LMK clock buffer for external clock connection. This means that user should pay attention on how external signal is connected, ensure proper voltage levels etc. If you supply external clock signal from signal generator, signal level should be around 10dBm. Note please, that LMK clock buffer expects positive voltage amplitude, while your generator may supply +/- voltage.

The proper way to supply the external reference clock: supply external clock firstfirst and then turn the board on. This is the only way to have proper operation of the board with external clock. If frequency is changed on the fly, CPU inside of FPGA gets messed up hence no control over the board.

Power Distribution

LimeSDR-Mini board is powered from USB port. LimeSDR-Mini board power delivery network consists of different power rails with different voltages, filters, power sequences. LimeSDR-Mini board power distribution block diagram is presented in Figure 9.

Figure 9. LimeSDR-Mini v1.1 board power distribution block diagram