Features: • Auto-restart and cycle by cycle current limiting functions handle both primary and secondary faults
• On-chip latching thermal shutdown protects the entire system against overloadApplicationUse a Kelvin connection to the SOURCE pin for the CONTROL pin bypass capacitor. Use single point grounding techniques at the SOURCE pin as shown in Figure 8. Use a ceramic high frequency decoupling capacitor to bypass noise transients which might appear on the CONTROL pin. The TOP412 and TOP414 have an over current latching shutdown feature. Failure to use a high frequency decoupling capacitor may allow incidental noise to accidentally trigger this feature.
Limit peak voltage and ringing on the DRAIN voltage at turnoff to a safe value. Use a Zener or TVS Zener diode to clamp the DRAIN voltage.
Do not plug the TOPSwitch device into a "hot" IC socket during test. External CONTROL pin capacitance may deliver a surge current sufficient to trigger the shutdown latch which turns the TOPSwitch off.
Under some conditions, externally provided bias or supply current driven into the CONTROL pin can hold the TOPSwitch in one of the 8 auto-restart cycles indefinitely and prevent starting. Shorting the CONTROL pin to the SOURCE pin will reset the TOPSwitch. To avoid this problem when doing bench evaluations, it is recommended that the VC power supply be turned on before the DRAIN voltage is applied.
CONTROL pin currents during auto-restart operation are much lower at low input voltages (< 20 V) which increases the autorestart cycle period (see the IC vs. Drain Voltage Characteristic curve).
In some cases, minimum loading may be necessary to keep a lightly loaded or unloaded output voltage within the desired range due to the minimum ON-time.
For additional applications information regarding the TOPSwitch family, refer to Web site, www.powerint.com.
SpecificationsDRAIN Voltage ............................................ -0.3 to 350 V
CONTROL Voltage ...................................... - 0.3 V to 9 V
Storage Temperature .............................. -65 to 150 °C
Operating Junction Temperature(2) ......... -40 to 150 °C
Lead Temperature(3) ......................................... 260 °C
Notes:
1. All voltages referenced to SOURCE, TA = 25 °C.
2. Normally limited by internal circuitry.
3. 1/16" from case for 5 seconds.
DescriptionThe TOPSwitch family implements, with only three terminals, all functions necessary for a DC to DC, converter: high voltage N-channel power MOSFET with controlled turn-on gate driver, voltage mode PWM controller with integrated 120 kHz oscillator, high voltage start-up bias circuit, bandgap derived reference,
bias shunt regulator/error amplifier for loop compensation and fault protection circuitry. Compared to discrete MOSFET and controller or self oscillating (RCC) switching converter solutions, a TOPSwitch integrated circuit can reduce total cost, component count, size, weight and at the same time increase efficiency and system reliability. This TOPSwitch device is well suited for Telecom, Cablecom and other DC to DC converter applications up to 21W of output power. Internally, the lead frame of the SMD-8 package uses six of its pins to transfer heat from the chip directly to the board, eliminating the cost of a heat sink.
TOP412 Data Sheet
