cy8c42123 Cypress Semiconductor Corporation., cy8c42123 Datasheet - Page 5

• Manufacturer Part Number: cy8c42123
• Description: Power Psoc? Devices
• Manufacturer: Cypress Semiconductor Corporation.

5.0
5.1
A white LED driver is a constant current power supply. By driving the same current through a set of LEDs in series, the intensity
of the LEDs can be closely matched. The CY8C42x23 Power PSoC can be configured as a constant voltage or constant current
boost supply. In this configuration, the HV
be generated. White LEDs typically have a forward voltage of around 4V, so in the five LED configuration shown in Figure 5-1
the LED drive voltage would have to be around 20V (plus allowance for the voltage losses in the FET and the current sense
resistor, R
Figure 5-1 shows an inductor, an NFET, a diode, and a capacitor configured as a boost converter with the CY8C42x23 as the
controller. The voltage on the capacitor is fed back through a voltage sense pin, VS0, and an attenuator, Atten0, to the comparator,
COMP0. The VS0 pin can be connected directly to a voltage higher than HV
The output of the comparator controls a single PSoC digital block configured as a PWM. The reference for the comparator is the
output of VDAC0. When the attenuator output exceeds the reference, the comparator will stop the PWM using the "Kill" input.
This creates a feedback loop that maintains the VS0 node at a voltage proportional to the VDAC0 setting. The Atten0 output is
also connected to the ADC so the control software can monitor the output voltage.
To maintain constant current, the voltage across the R
where it is monitored. The control software adjusts the VDAC0 setting, based on current sense measurements, to achieve the
desired current through the load.
5.1.1
This application could connect the R
digital blocks, half of the high voltage resources, one VDAC, two IDACs, seven of the analog multiplexer channels to the ADC,
and over 90% of the CPU available for other tasks.
Document 38-12034 Rev. *C
Boost Converter White LED Driver
Typical Power PSoC Applications
Resources
ISENSE
HVO[1]
GDO1
HVdd
P0[7]
P0[5]
P0[3]
P0[1]
P1[1]
VS1
HVdd
).
Kill
Low Drop-Out
Reg ulator
IDAC1
HV Driver
PWM DB
COMP 1
DCB00
DBC01
PWM primary
VDAC1
Internal Vdd
ODAC1
ODAC1
AM uxBus3
AM uxBus1
PRELIMINARY
Atten1
ISENSE
DCB01
VDAC1
Figure 5-1. Boost Converter White LED Driver
DIGITAL SECTION
dd
resistor to any of the GPIO pins (P0[7:0] and P1[1:0]). The Power PSoC still has three
Convertor
Analog to
voltage is lower than required to drive the LEDs in series and a higher voltage must
Dig ital
IBIAS
VBG
ANALOG and HIGH V OLTAGE
VDAC0
DBD02
AMuxBus2
AMuxBus0
SECTIONS
ODAC0
Atten0
ODAC0
ISENSE
VDAC0
resistor is routed through pin P0[4] and AMuxBus0 to the ADC
DBC00
DCD03
HV Driver
COMP 0
IDAC0
dd
GDO0
VS0
HVO[0]
P0[6]
P0[4]
P0[2]
P0[0]
P1[0]
, so no external signal level conversion is needed.
HVdd
CY8C42123/CY8C42223
CY8C42323/CY8C42423
Q1
R
ISEN SE
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