CY8C41223 데이터 시트보기 (PDF) - Cypress Semiconductor

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CY8C41223

Linear Power PSoC™ Devices

Cypress Semiconductor 

PRELIMINARY

CY8C41123 and CY8C41223

5.0 Typical Linear Power PSoC Applications

5.1 Linear White LED Driver

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 CY8C41x23 Linear Power PSoC can be configured as a constant voltage or constant

current linear supply. In this configuration, the HVdd voltage is high enough to drive the LEDs in series and current regulation is

needed. White LEDs typically have a forward voltage of around 4V, so in the four LED configuration shown in Figure 5-1, HVdd

would have to be around 16V (plus allowance for voltage losses in the FET and the current sense resistor, RISENSE). The HVdd

voltage is converted to 5V by the internal Low Drop-Out Regulator for use by the Power PSoC Core.

To maintain constant voltage, the gate of the External PFET is controlled by the GDO0 pin and driven in a linear mode. The voltage

at the top of the load, connected to VS0, is attenuated by the internal resistive element, Atten0. The voltage out of the attenuator

is fed into the positive terminal of an amplifier configured as a voltage follower. The amplifier's negative input is connected to the

output of the voltage DAC, VDAC0. 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 RISENSE resistor is routed through pin P0[4] and AMuxBus0 to the ADC

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 Resources

This application could connect the RISENSE resistor to any of the GPIO pins (P0[7:0] and P1[1:0]). The Linear Power PSoC still

has all of its digital resources, 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.

HVdd

HVdd

GDO1

VS1

P0[7]

P0[5]

P0[3]

P0[1]

P1[1]

LowDrop-Out

Reg ul ator

InternalVdd

ANALOG and HIGH VOLTAGE

SECTIONS

ODAC1

VDAC1

VBG

ODAC0

VDAC0

VDAC1 IBIAS VDAC0

Analog to

D ig ital

Convertor

Atten1

AMuxBus3

AMuxBus1

Atten0

AMuxBus2

AMuxBus0

COMP1

ODAC1

ODAC0

COMP0

GDO0

VS0

P0[6]

P0[4]

P0[2]

P0[0]

P1[0]

HVdd

Ext.

PFET

RISENSE

Figure 5-1. Linear White LED Driver

Document 001-00360 Rev. *A

Page 5 of 36

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