Datasheet CAT4101 (ON Semiconductor) - 8
| Manufacturer | ON Semiconductor |
| Description | 1 A Constant-Current LED Driver with PWM Dimming |
| Pages / Page | 10 / 8 — CAT4101. Application Information Single 12 V Supply. Recommended. Layout. … |
| File Format / Size | PDF / 220 Kb |
| Document Language | English |
CAT4101. Application Information Single 12 V Supply. Recommended. Layout. Figure 16. Single Supply Driving Three LEDs
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CAT4101 Application Information Single 12 V Supply
For a given package style and board layout, the operating The circuit shown in Figure 16 shows how to power three junction temperature TJ is a function of the power LEDs in series from a single 12 V supply using the dissipation PD, and the ambient temperature, resulting in the CAT4101. The CAT4101 can not be driven directly from following equation: 12 V, three components are needed to create a lower voltage T for the VIN pin (below 5.5 V). Resistor R2 and zener diode J + TAMB ) PD(qJC ) qCA) + TAMB ) PD qJA D provide a regulated voltage while the quiescent current The CAT4101 TO−263 5−lead package provides a thermal runs through the N−Channel transistor M. Suitable parts for resistance when the ground tab is soldered down to the PCB. this circuit are the ON Semiconductor MM3Z6V2 zener When mounted on a double−sided printed circuit board with diode and the 2N7002L N−channel transistor (SOT23 two square inches of copper allocated for “heat spreading”, package). the resulting qJA is about 30°C/W. For example, at 60°C ambient temperature, the maximum power dissipation is calculated as follow: 12 V C2 R2 T 1 mF 5 kW P Jmax * TAMB + 150 * 60 M Dmax + qJA 30 + 3 W D 6.2 V
Recommended Layout
VIN LED The board layout should provide good thermal dissipation C1 0.1 mF through the PCB. Multiple via can be used to connect the tab
CAT4101
of the CAT4101 to a large ground plane underneath the package. EN/PWM Input capacitor C1 should be placed as close to the driver RSET IC as possible. The RSET resistor should have a Kelvin R1 GND connection to the GND pin of the CAT4101.
Figure 16. Single Supply Driving Three LEDs Power Dissipation
The power dissipation (PD) of the CAT4101 can be calculated as follows: PD + (VIN IIN) (VLED ILED) where VLED is the voltage at the LED pin. Combinations of high VLED voltage or high ambient temperature can cause the CAT4101 to enter thermal shutdown. In applications where VLED is high, a resistor can be inserted in series with the LED string to lower PD. Thermal dissipation of the junction heat consists primarily of two paths in series. The first path is the junction to the case (qJC) thermal resistance which is defined by the package style, and the second path is the case to ambient (qCA) thermal resistance, which is dependent on board layout. The overall junction to ambient (qJA) thermal resistance is equal to: qJA + qJC ) qCA
Figure 17. CAT4101 Recommended Layout http://onsemi.com 8
CAT4101 Application Information Single 12 V Supply
For a given package style and board layout, the operating The circuit shown in Figure 16 shows how to power three junction temperature TJ is a function of the power LEDs in series from a single 12 V supply using the dissipation PD, and the ambient temperature, resulting in the CAT4101. The CAT4101 can not be driven directly from following equation: 12 V, three components are needed to create a lower voltage T for the VIN pin (below 5.5 V). Resistor R2 and zener diode J + TAMB ) PD(qJC ) qCA) + TAMB ) PD qJA D provide a regulated voltage while the quiescent current The CAT4101 TO−263 5−lead package provides a thermal runs through the N−Channel transistor M. Suitable parts for resistance when the ground tab is soldered down to the PCB. this circuit are the ON Semiconductor MM3Z6V2 zener When mounted on a double−sided printed circuit board with diode and the 2N7002L N−channel transistor (SOT23 two square inches of copper allocated for “heat spreading”, package). the resulting qJA is about 30°C/W. For example, at 60°C ambient temperature, the maximum power dissipation is calculated as follow: 12 V C2 R2 T 1 mF 5 kW P Jmax * TAMB + 150 * 60 M Dmax + qJA 30 + 3 W D 6.2 V
Recommended Layout
VIN LED The board layout should provide good thermal dissipation C1 0.1 mF through the PCB. Multiple via can be used to connect the tab
CAT4101
of the CAT4101 to a large ground plane underneath the package. EN/PWM Input capacitor C1 should be placed as close to the driver RSET IC as possible. The RSET resistor should have a Kelvin R1 GND connection to the GND pin of the CAT4101.
Figure 16. Single Supply Driving Three LEDs Power Dissipation
The power dissipation (PD) of the CAT4101 can be calculated as follows: PD + (VIN IIN) (VLED ILED) where VLED is the voltage at the LED pin. Combinations of high VLED voltage or high ambient temperature can cause the CAT4101 to enter thermal shutdown. In applications where VLED is high, a resistor can be inserted in series with the LED string to lower PD. Thermal dissipation of the junction heat consists primarily of two paths in series. The first path is the junction to the case (qJC) thermal resistance which is defined by the package style, and the second path is the case to ambient (qCA) thermal resistance, which is dependent on board layout. The overall junction to ambient (qJA) thermal resistance is equal to: qJA + qJC ) qCA
Figure 17. CAT4101 Recommended Layout http://onsemi.com 8
