EmStat Pico Specifications :: PalmSens Documentation for Developers

Features

Analog

5 analog inputs including 2 high impedance (1 TΩ)
2 current measurement channels each with max. current of ±3 mA and min. resolution of 5.5 pA on lowest current range
16-bit, analog-to-digital converter (ADC)
Two 12-bit voltage output DACs, range 0.2 to 2.4 V (±2.2 V voltage potential to sensor)
Two potentiostat circuits with impedance measurement capability <10 Ω to 100 MΩ,
0.016 Hz to 200 kHz
Internal temperature sensor, ±2°C accurate

Digital

UART
I2C
SPI
8 GPIO
SD card support

Dimensions

30.5 mm X 18 mm X 2.6 mm

Functional block diagram

Figure 1. EmStat Pico functional block diagram

Mechanical drawing

Figure 2. EmStat Pico module dimensions (all values in millimeters)

Pinout

Figure 3. EmStat Pico pinout

Pin functions

Table 1. Pin function description
Pin No.	Name	Type	Description
1	N/C	Reserved	Factory use only
2	RX	DIO	UART receive. Baud rate: 230400 Bd
3	TX	DIO	UART transmit. Baud rate: 230400 Bd
4	/DWN	DIO	Initiates bootmode. Firmware download begins on exiting reset. (Active Low). This pin is pulled up to 3.3 V by a 10 kΩ resistor.
5	/RST	DIO	Resets the module processor. (Active Low). This pin is pulled up to 3.3 V by a 10 kΩ resistor.
6	GPIO_0	DIO	General-Purpose Input/Output Port 0 / PWM Output. This pin defaults as tri-state.
7	GPIO_1	DIO	General-Purpose Input/Output Port 1 / SPI_MISO. This pin defaults as tri-state.
8	DGND	GND	High speed digital signal GND return. The module has a single continuous Gnd plane.
9	GPIO_2	DIO	General-Purpose Input/Output Port 2 / SPI_CLK. This pin defaults as tri-state.
10	GPIO_3	DIO	General-Purpose Input/Output Port 3 / SPI_MOSI. This pin defaults as tri-state.
11	GPIO_4	DIO	General-Purpose Input/Output Port 4 / SPI_CS. This pin defaults as tri-state.
12	CE_1	V_out	Potentiostat 1 output. This pin is connected to a Counter Electrode when measuring electrochemical sensors. Optionally, this pin can be used as a DAC output.
13	WE_1	I_in	Potentiostat 1 current measurement TIA input. For electrochemical measurements this pin is connected to the Working Electrode.
14	RE_1	V_in	Potentiostat 1 high impedance reference input. For electrochemical measurements this pin is connected to the Reference Electrode. Optionally, this pin can be used as an ADC input. If unused, it is recommended to connect this pin to AGND.
15	AGND	GND	Analog signal Gnd. The module has a single continuous Gnd plane.
16	RE_0	V_in	Potentiostat 0 high impedance reference input. For electrochemical measurements this pin is connected to the Reference Electrode. Optionally, this pin can be used as an ADC input. it is recommended to connect this pin to AGND.
17	WE_0	I_in	Potentiostat 0 current measurement TIA input. For electrochemical measurements this pin is connected to the Working Electrode.
18	CE_0	V_out	Potentiostat 0 output. This pin is connected to a Counter Electrode when measuring electrochemical sensors. Optionally, this pin can be used as a DAC output.
19	Ain_2	V_in	ADC Input / 1.82 V buffered voltage reference. Decouple reference to GND via a 100 pF capacitor. The maximum load current = 200 μA.
20	Ain_1	V_in	ADC Input.
21	Ain_0	V_in	ADC Input.
22	GPIO_5	DIO	General-Purpose Input/Output Port 5. This pin defaults as tri-state.
23	GPIO_6/CD	DIO	General-Purpose Input/Output Port 6. Card Detect input for use with SD cards. This pin defaults as tri-state.
24	GPIO_7	DIO	General-Purpose Input/Output Port 7 / WAKE. This pin is pulled up to 3.3 V in Sleep and Hibernate modes and is used to wake the device. This pin defaults as tri-state.
25	I2C_SCL	DIO	Interface Clock for I²C. This pin is pulled up to 3.3 V by a 10 kΩ resistor.
26	I2C_SDA	DIO	Interface Data for I²C. This pin is pulled up to 3.3 V by a 10 kΩ resistor.
27	V_IN	Power	3.5 V to 5.5 V vs GND.
28	DGND	GND	Power supply GND return. Module has a single continuous GND plane.

Absolute maximum ratings

Parameter	Rating
V_IN to GND	-0.3 V to +6.5 V (see ADP166)
Analog Input Voltage to GND	-0.3 V to +3.6 V
Digital Input Voltage to GND	-0.3 V to +3.6 V
Total Positive GPIO Pins Current	30 mA
Total Negative GPIO Pins Current	-30 mA
Storage temperature	-65 °C to +100 °C
Operating temperature	-40 °C to +85 °C
ESD Human Body Model (HBM)	4 kV
ESD Field-Induced Charged Device Model (FICDM)	1 kV
Hand Soldering (10 seconds per pin)	400 °C
Reflow temperature	245 °C

Parameter

Rating

V_IN to GND

-0.3 V to +6.5 V (see ADP166)

Analog Input Voltage to GND

-0.3 V to +3.6 V

Digital Input Voltage to GND

-0.3 V to +3.6 V

Total Positive GPIO Pins Current

30 mA

Total Negative GPIO Pins Current

-30 mA

Storage temperature

-65 °C to +100 °C

Operating temperature

-40 °C to +85 °C

ESD Human Body Model (HBM)

4 kV

ESD Field-Induced Charged Device Model (FICDM)

1 kV

Hand Soldering (10 seconds per pin)

400 °C

Reflow temperature

245 °C

Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability.

Electrical specifications

Table 2. EmStat Pico electrical characteristics. Determined at 25 °C.
Parameter	Min	Typ	Max	Unit	Details
ADC
Input Voltage Range	0.2		2.1	V
Data Rate		800		kSPS
Resolution	16			Bits

Analog inputs
Leakage Current	-1.5	±0.5	1.5	nA	Ain_0 to Ain_3, WE_0, WE_1 (OFF)
Leakage Current		±10		pA	RE_0, RE_1

EIS measurement
Frequency range	0.016		200k	Hz
Excitation Amplifier Bandwidth		3		MHz
Impedance Measurement Range	10		10M	Ω

Potentiostat circuit (Low speed)
WE Input Bias Current		80	300	pA	WE input, 25 °C
RE Input Bias Current		10		pA	RE input, 25 °C
Offset voltage		50	150	μV
Source/Sink current	-3		3	mA
Applied potential accuracy		0.04	0.2	%
Current Range accuracy		0.1	< 0.5%	%	±0.1% of range offset
Max bandwidth > 100 nA CR		100 Hz
Max bandwidth 100 nA CR		16 Hz

Potentiostat circuit (High speed)
WE Input Bias Current		1		nA	WE input, 25 °C
RE Input Bias Current		10		pA	RE input, 25 °C
Offset voltage		50	150	μV
Source/Sink current	-3		3	mA
Applied potential accuracy		0.1	0.5	%
Current Range accuracy		0.2	1.0	%	±0.1% of range offset
Max bandwidth > 6 μA CR	10		3000	kHz
Max bandwidth 6 μA CR		5		kHz
Max bandwidth 1 μA CR		800		Hz
Max bandwidth 100 nA CR		80		Hz

DAC
Resolution	12			Bits
Voltage Range (Low speed)	0.2		2.4	V
Voltage Range (High speed)		±0.607		V	On a bias point fixed by the Low Speed DAC
Low and High Combined	0.2		2.8	V

Buffered reference voltage output
Voltage	1.815	1.82	1.825	V	TA = 25°C, capacitive load to ground 100 pF
Load Current			200	μA

GPIO
Input Voltage Low			0.825	V
Input Voltage High	1.88			V
Output Voltage Low			0.3	V	Sink current = 2 mA
Output Voltage High	2.9			V	Source current = 2 mA
Short-Circuit Current		11.5		mA

Temperature sensor (default ADuCM355)
Resolution		0.3		°C
Accuracy		±2		°C

Temperature sensor (optional ADT7420)
Resolution		0.0078		°C
Accuracy		±0.25		°C

Power requirements
V_IN voltage range	3.5	5	5.5	V
Normal (High speed 1 Chan)		30		mA
Normal (Low speed 1 Chan)		10		mA
Normal (Low speed 2 Chan)		15		mA
Sleep (Static 1 Chan)		8		mA
Sleep (Static 2 Chan)		13		mA
Hibernate mode		10		μA

For more detailed specs see datasheets for ADuCM355, ADT7420, ADP166 and AD8606.

Power supply

The EmStat Pico has an on-board 3.3 V LDO (ADP166) and supply filtering. This provides clean operation from a USB or a 3.5 V to 5.5 V supply. Driving the EmStat Pico V_IN directly from a switching regulator may introduce measurement noise. Care should be taken to provide clean power to the V_IN pin.

Power modes
Normal mode	CPU running. PSTAT channels configured by the user (OFF, OCP, Low Speed, High Speed). Measurement performed.
Sleep mode	CPU is not running. PSTAT channels configured by the user (OFF, OCP, Low Speed, High Speed). All voltages are still applied, but no measurements can be done.
Hibernate	CPU is not running. PSTAT channels are OFF.

Power modes

Normal mode

CPU running. PSTAT channels configured by the user (OFF, OCP, Low Speed, High Speed). Measurement performed.

Sleep mode

CPU is not running. PSTAT channels configured by the user (OFF, OCP, Low Speed, High Speed). All voltages are still applied, but no measurements can be done.

Hibernate

CPU is not running. PSTAT channels are OFF.

Digital interface

The EmStat Pico features the following digital interfaces:

UART with baud rate of 230400 Bd
SPI port with SD card support. (EmStat Pico as master only). For SPI timings see ADuCM355.
I2C port. (EmStat Pico as master only). Note: The ADT7420 temperature sensor is connected to this bus and both the SCL and SDA lines have 10 kΩ pullup resistors to 3.3 V
1 PWM output
8 GPIO

Calibration

The EmStat Pico has on-board 1 kΩ and 100 kΩ precision resistors (accuracy: ±0.1%, temperature coefficient: ±25 ppm/°C) for self-calibration.

Analog interface

DAC modes

The EmStat Pico has 2 low speed DACs and one high speed DAC. The 2 low speed DACs have an output range of 0.2 V to 2.4 V and can be used simultaneously. The single high speed DAC has an output range of ±0.607 V on a bias point fixed by the low speed DAC.

A low speed DACs and the high speed DAC can be combined to achieve an output range 0.2 V to 2.8 V. This can be done on one channel at a time.

Potentiostat channels

The applied cell potential is the voltage between RE and WE (voltage supplied at CE and controlled at RE by potentiostat loop) of the Potentiostat Channel. WE is maintained at a potential between 0.819 V and 2.366 V to allow headroom for the TIA to operate. Thus the applied potential ranges are:

high speed DAC: -1.981 V to 2.166 V.

low speed DAC: -1.581 V to 2.166 V.

The EmStat Pico uses the 2 potentiostat channels of the ADuCM355 with the addition of high impedance buffers (AD8606) on the RE inputs. See links below for further details.

Analog inputs

The EmStat Pico features a 16-bit, 800 kSPS, successive approximation register (SAR) analog-to-digital converter (ADC) with multiplexer, input buffers, built-in anti-aliasing filter (AAF), and programmable gain amplifier (PGA). The input range of 0.2 V to 2.1 V. The multiplexer switches between the analog input channels (Ain_0 to Ain_2) and the current and voltage measurement channels of PSTAT_0 and PSTAT_1. For further details see ADuCM355 documentation.

Layout

Surface mount PCB footprint

Figure 6 shows the recommended SMT footprint for the EmStat Pico for hand soldering directly to a PCB using the castellated pads. Pads are 3 mm long by 1.5 mm wide.

Figure 4. EmStat Pico surface mount footprint

Through hole PCB footprint

Figure 7 shows the recommended through hole footprint for the EmStat Pico for mounting with Samtec TS-112-T-A-1 pins. Pads are 1.5 mm diameter with 0.8 mm diameter hole spaced on a 2.54 mm (100 mil) grid.

Figure 5. EmStat Pico through-hole footprint. Grid is 2.54 mm (100 mil)

Layout considerations

The EmStat Pico has 3 GND pins. Pin 28 is the power supply GND return. Pin 8 is located beside the SPI lines to provide a high speed digital GND return. Pin 15 is located beside the Analog pins to reference single ended analog signals and to connect to external shielding. The module has a single continuous GND plane, so all 3 pins are connected together.

When laying out a PCB to carry the EmStat Pico it is recommended to use a single continuous GND plane and to zone the board as shown in Figure 8. If desired, separate analog and digital GND planes can be used with the EmStat Pico providing the connection between the two planes.

Figure 6. Recommended PCB zoning

Assembly

SMT board-to-board soldering

The EmStat Pico has castellated pads on each side to allow surface mount board-to-board soldering. It is recommended to use hand soldering onto the footprint detailed above using a 1.2 mm chisel tip at 370°C and dwell for no more than 10 seconds on each pad.

SMT reflow information

The EmStat Pico has a Moisture Sensitivity Level (MSL) of 3.

Recommended reflow temperature is maximum 245 °C.

Pin mount

The EmStat Pico through hole pads have an internal diameter of 0.76 mm (30 mil). These are designed to accept 0.64 mm (25 mil) diameter pins such as Samtec TS-112-T-A-1. The through hole pads are located on a 2.54 mm (100 mil) grid to match standard prototyping board. It is recommended to hand solder the pins into the EmStat Pico using a 1.2 mm chisel tip at 370°C and dwell for no more than 10 seconds on each pad. Use Low Residue Tin (No-Clean Flux Core Solder).

Changes in specifications and typing errors reserved. Every effort has been made to ensure the accuracy of this document. However, no rights can be claimed by the contents of this document.