ZXLD1362 Operation
In normal operation, when voltage is applied at +VIN, the ZXLD1362 internal NDMOS switch is turned on. Current starts to flow through sense resistor R1, inductor L1, and the LEDs. The current ramps up linearly, and the ramp rate is determined by the input voltage +VIN and the inductor L1. This rising current produces a voltage ramp across R1. The internal circuit of the ZXLD1362 senses the voltage across R1 and applies a proportional voltage to the input of the internal comparator. When this voltage reaches an internally set upper threshold, the NDMOS switch is turned off. The inductor current continues to flow through R1, L1, the LEDs, the Schottky diode D1, and back to the supply rail, but it decays, with the rate of decay determined by the forward voltage drop of the LEDs and the Schottky diode. This decaying current produces a falling voltage at R1, which is sensed by the ZXLD1362. A voltage proportional to the sense voltage across R1 is applied at the input of the internal comparator. When this voltage falls to the internally set lower threshold, the NDMOS switch is turned on again. This
ZXLD1362EV1 Evaluation Board - BOM
Ref | Value | Package | Part Number | Manufacturer | Notes |
R1 | 0.15R | 0805 | CRL1220 R15TD | Tyco | 5%, 200ppm |
R2 | 1kΩ | 0805 | Generic | - | - |
C1 | 10uF 100V | SMD | NACEW100M1006.3x8TR13F | NIC | Electrolytic - 20% |
C2,C4 | 100nF, 100V | 0805 | NMC0805X7R104K100TRPLPF | NIC | 20% |
C3 | 100nF | 1206 | NMC1206X7R104K100TRPLP3KF | NIC |
|
L1 | 68uH | - | NPIS24H680MTRF | NIC | 68uH/1.5A rms |
D1 | 100V, 3A | SMC | 30BQ100PBF | IR | Schottky diode |
U1 | ZXLD1362 |
| ZXLD1362E5TA | Zetex |
|
The aluminium PCB guarantees a good thermal dissipation for the ZXLD1362 device, which can produce up to 1 watt of heat under maximum load conditions. Other sources of heat are the Schottky diode, the inductor and the sense resistor. Care must be taken in their placement.
Warning: At 60V operation with 700mA output, the board temperature rises by around 50C from ambient after 30 minutes of operation.
Figure 3: Component layout and circuit board view
ZXLD1362EV3 User Guide issue 1 | 4/7 |
