CY8C54 Datasheet, PDF (51/93 Pages) Cypress Semiconductor – Programmable System-on-Chip (PSoC)

PRELIMINARY
PSoC^®5: CY8C54 Family Data Sheet
and possible resistor settings for the PGA. The gain is switched
from inverting and non inverting by changing the shared select
value of the both the input muxes. The bandwidth for each gain
case is listed in Table 8-2.
Table 8-2. Bandwidth
Gain
Bandwidth
1
6.0 MHz
24
340 kHz
48
220 kHz
50
215 kHz
Figure 8-8. Continuous Time TIA Schematic
R fb
I _in
V ref
Vout
Figure 8-7. PGA Resistor Settings
V_in
0
V_ref
1
S
V_ref
0
V_in
1
R1
20k or 40k
R2
20k to 980k
The PGA is used in applications where the input signal may not
be large enough to achieve the desired resolution in the ADC, or
dynamic range of another SC/CT block such as a mixer. The gain
is adjustable at runtime, including changing the gain of the PGA
prior to each ADC sample.
8.5.4 TIA
The Transimpedance Amplifier (TIA) converts an internal or
external current to an output voltage. The TIA uses an internal
feedback resistor in a continuous time configuration to convert
input current to output voltage. For an input current Iin, the output
voltage is Iin x Rfb +Vref, where Vref is the value placed on the
non inverting input. The feedback resistor Rfb is programmable
between 20 KΩ and 1 MΩ through a configuration register.
Table 8-3 shows the possible values of Rfb and associated
configuration settings.
Table 8-3. Feedback Resistor Settings
Configuration Word
000b
Nominal R_fb (KΩ)
20
001b
30
010b
40
011b
60
100b
120
101b
250
110b
500
111b
1000
The TIA configuration is used for applications where an external
sensor's output is current as a function of some type of stimulus
such as temperature, light, magnetic flux etc. In a common appli-
cation, the voltage DAC output can be connected to the VREF
TIA input to allow calibration of the external sensor bias current
by adjusting the voltage DAC output voltage.
8.6 LCD Direct Drive
The PSoC Liquid Crystal Display (LCD) driver system is a highly
configurable peripheral designed to allow PSoC to directly drive
a broad range of LCD glass. All voltages are generated on chip,
eliminating the need for external components. With a high
multiplex ratio of up to 1/16, the CY8C54 family LCD driver
system can drive a maximum of 736 segments. The PSoC LCD
driver module was also designed with the conservative power
budget of portable devices in mind, enabling different LCD drive
modes and power down modes to conserve power.
PSoC Creator provides an LCD segment drive component. The
component wizard provides easy and flexible configuration of
LCD resources. You can specify pins for segments and
commons along with other options. The software configures the
device to meet the required specifications. This is possible
because of the programmability inherent to PSoC devices.
Key features of the PSoC LCD segment system are:
„ LCD panel direct driving
„ Type A (standard) and Type B (low power) waveform support
„ Wide operating voltage range support (2V to 5V) for LCD
panels
„ Static, 1/2, 1/3, 1/4, 1/5 bias voltage levels
„ Internal bias voltage generation through internal resistor ladder
„ Up to 62 total common and segment outputs
„ Up to 1/16 multiplex for a maximum of 16 backplane/common
outputs
„ Up to 62 front plane/segment outputs for direct drive
„ Drives up to 736 total segments (16 backplane x 46 front plane)
„ Up to 128 levels of software controlled contrast
„ Ability to move display data from memory buffer to LCD driver
through DMA (without CPU intervention)
„ Adjustable LCD refresh rate from 10 Hz to 150 Hz
Document Number: 001-55036 Rev. *A
Page 51 of 93
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