Datasheet
Table Of Contents
- Figure 1. Typical application circuit
- 1 Pin settings
- 2 Maximum ratings
- 3 Electrical characteristics
- 4 Functional description
- 5 Application notes - buck conversion
- 5.1 Closing the loop
- 5.2 GCO(s) control to output transfer function
- 5.3 Error amplifier compensation network
- 5.4 LED small signal model
- 5.5 Total loop gain
- 5.6 Compensation network design
- 5.7 Example of system design
- 5.8 Dimming operation
- 5.9 Component selection
- 5.10 Layout considerations
- 5.11 Thermal considerations
- 5.12 Short-circuit protection
- 5.13 Application circuit
- 6 Application notes - alternative topologies
- 7 Package mechanical data
- 8 Ordering information
- 9 Revision history
Functional description LED5000
12/51 Doc ID 023951 Rev 1
During normal operation a new soft-start cycle takes place in case of:
● thermal shutdown event
● UVLO event
The soft-start is disabled during the dimming operation to maximize the dimming
performance.
4.4 Dimming block
The DIM input features the LED brightness control with the PWM dimming operation (see
Chapter 5.8
).
4.5 Inhibit block
The inhibit block features the standby mode accordingly with
Table 5: Electrical
characteristics
. The INH pin high level disables the device so the power consumption is
reduced to less than 40 µA. The INH pin is 5 V tolerant.
4.6 Error amplifier
The voltage error amplifier is the core of the loop regulation. It is a transconductance
operational amplifier whose non inverting input is connected to the internal voltage
reference (200 mV), while the inverting input (FB) is connected to the output current sensing
resistor.
The error amplifier output is compared with the inductor current sense information to
perform PWM control.
4.7 Thermal shutdown
The shutdown block generates a signal that disables the power stage if the temperature of
the chip goes higher than a fixed internal threshold (150±10 °C typical). The sensing
element of the chip is close to the PDMOS area, ensuring fast and accurate temperature
detection. A 15 °C typical hysteresis prevents the device from turning ON and OFF
continuously during the protection operation.
Table 6. Uncompensated error amplifier characteristics
Description Values
Transconductance 2200 µS
Low frequency gain 90 dB