MAX32600 User’s Guide
Analog Front End
8.5 LED
8.5.2.1
Basic LED Configuration
Figure 8.11: Basic LED Configuration
In the most basic LED configuration, an op amp is used to regulate the current (observed as a voltage on an external sense resistor) to match the voltage command
from a DAC. The op amp drives the gate of an NMOS switch transistor in the I/O; the I/O regulates digitally whether the switch in the I/O is connected to the op amp
or turned off. The
MAX32600
I/O switch can drive up to 100mA. This configuration requires two GPIO pins to implement the switch transistor and activate the LED.
The value of Rs is chosen to trade-off current resolution and available voltage for the LED. As the value of Rs is decreased, the resolution of the current selection is
reduced and more voltage is available for the LED; as the value of Rs is increased, the resolution of the current selection is increased and less voltage is available
for the LED.
Rev.1.3 April 2015
Maxim Integrated
Page 473