RT4533 Asynchronous Boost Converter for 10 WLEDs

General Description

The RT4533 is a highly integrated LED driver IC capable of driving 10 WLEDs in series. It is composed of a current mode Boost converter integrated with a 36.5V/1.2A power switch. The RT4533 supports a wide input voltage range from 2.5V to 5.5V, and runs at a fixed frequency of 1.1MHz. The LED current is set via an external resistor and the feedback voltage is regulated to 200mV. For brightness dimming, the RT4533 supports PWM dimming which determines the feedback reference voltage.

Performance Sepcification Summary

Summary of the RT4533GJ6 Evaluation Board performance specificiaiton is provided in Table 1. The ambient temperature is 25°C.

Table 1. RT4533 Evaluation Board Performance Specification Summary

Power-up Procedure

Suggestion Required Equipments

• RT45336GJ6 Evaluation Board
• DC power supply capable of at least 6V and 2A
• Function Generator
• Oscilloscope

Proper measurement equipment setup and follow the procedure below.

1. Apply 3.6V nominal input power supply (2.5V < V_IN < 5.5V) to the VIN and GND terminals.

2. The EN voltage is pulled to logic high by internal circuit to enable operation. Drive EN high (> 1.4V) to enable operation or low (< 0.4V) to disable operation. Pull EN pin to High pin that make EN voltage equal to VIN.

3. There is a 3-pin header JP5 “EN” for enable control. To use a jumper at “H” option to tie EN test pin to input power VIN for enabling the device. Inversely, to use a jumper at “L” option to tie EN test pin and ground GND for disabling the device. The JP5 is also the PWM control pin.

4. The I_LED setting supports PWM dimming as below.

Output I_LED Setting

1. PWM Brightness Dimming

The EN pin is used for the control input for both PWM dimming mode and digital dimming mode. Shutdown delay when the EN voltage is logic low for more than specific time, the driver will be shut down.

2. OCP

The driver provides cycle-by-cycle current limit function to control the current on power switch. The boost switch turns off when the inductor current reaches this current threshold and it remains off until the beginning of the next switching cycle. This protects the RT4533 and external component under overload conditions.

3. OVP

The Over Voltage Protection is detected by a resistor divider circuit from VOUT. Once VOUT goes over the OVP voltage, LX pin stops switching and the power N-MOSFET will be turned off. Then, the VOUT will be discharged by external resistor. OVP will be released until EN goes from Lo to Hi again.

4. OTP

As the die temperature is higher than 160°C, the chip also will enter protection mode. The power MOSFET will be turned off during protection mode to prevent abnormal operation. The device is released from shutdown automatically when the junction temperature decreases by 15°C.

Detailed Description of Hardware

Headers Description and Placement

Carefully inspect all the components used in the EVB according to the following Bill of Materials table, and then make sure all the components are undamaged and correctly installed. If there is any missing or damaged component, which may occur during transportation, please contact our distributors or e-mail us at evb_service@richtek.com.

Test Points

The EVB is provided with the test points and pin names listed in the table below.

Bill of Materials

Typical Applications

EVB Schematic Diagram

Measure Result

Evaluation Board Layout

Figure 1. Top View (1^st layer)

Figure 2. Bottom View (2^nd Layer)