Cypress CY8C21434 Analog System, Additional System Resources, Array, Analog Multiplexer System

CY8C21634, CY8C21534 CY8C21434, CY8C21334, CY8C21234

The Analog System

The Analog System consists of 4 configurable blocks that allow the creation of complex analog signal flows. Analog peripherals are very flexible and may be customized to support specific application requirements. Some of the common PSoC analog functions for this device (most available as user modules) are:

■Analog-to-digital converters (single or dual, with 8-bit or 10-bit resolution)

■Pin-to-pin comparator

■Single-ended comparators (up to 2) with absolute (1.3V) reference or 8-bit DAC reference

■1.3V reference (as a System Resource)

In most PSoC devices, analog blocks are provided in columns of three, which includes one CT (Continuous Time) and two SC (Switched Capacitor) blocks. The CY8C21x34 devices provide limited functionality Type “E” analog blocks. Each column contains one CT Type E block and one SC Type E block. Refer to the PSoC Programmable System-on-Chip™ Technical Reference Manual for detailed information on the CY8C21x34’s Type E analog blocks.

Figure 2. Analog System Block Diagram

	Array Input
	Configuration
	ACI0[1:0]	ACI1[1:0]
	All IO
X
X
X	ACOL1MUX
X	AnalogMuxBus
X		Array
	ACE00	ACE01
	ASE10	ASE11

The Analog Multiplexer System

The Analog Mux Bus can connect to every GPIO pin. Pins may be connected to the bus individually or in any combination. The bus also connects to the analog system for analysis with comparators and analog-to-digital converters. An additional 8:1 analog input multiplexer provides a second path to bring Port 0 pins to the analog array.

Switch control logic enables selected pins to precharge continuously under hardware control. This enables capacitive measurement for applications such as touch sensing. Other multiplexer applications include:

■Track pad, finger sensing.

■Chip-wide mux that allows analog input from any IO pin.

■Crosspoint connection between any IO pin combinations.

When designing capacitive sensing applications, refer to the signal-to-noise system level requirement found in Application Note AN2403 on the Cypress web site at http://www.cypress.com.

Additional System Resources

System Resources, some of which are listed in the previous sections, provide additional capability useful to complete systems. Additional resources include a switch mode pump, low voltage detection, and power on reset. Brief statements describing the merits of each system resource follow.

■Digital clock dividers provide three customizable clock frequencies for use in applications. The clocks may be routed to both the digital and analog systems. Additional clocks can be generated using digital PSoC blocks as clock dividers.

■The I2C module provides 100 and 400 kHz communication over two wires. Slave, master, and multi-master modes are all supported.

■Low Voltage Detection (LVD) interrupts can signal the application of falling voltage levels, while the advanced POR (Power On Reset) circuit eliminates the need for a system supervisor.

■An internal 1.3 voltage reference provides an absolute reference for the analog system, including ADCs and DACs.

■An integrated switch mode pump (SMP) generates normal operating voltages from a single 1.2V battery cell, providing a low cost boost converter.

■Versatile analog multiplexer system.

Document Number: 38-12025 Rev. *O Page 3 of 45

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