TSI 10N Series — 10 Watt Step-Down Switching Regulator Application Note 1. General: This new generation of step-down switching regulator provides designers with a very cost-effective solution for converting a 5VDC, 12VDC or 24VDC voltage. To achieve highest efficiency (up to 93%) these dc/dc regulators are using latest technologies, as amorphous ferrite core, solid aluminium electrolyte capacitors and a synchronous commutation IC. A very high efficiency allows operation without additional heatsink with full load up to an operating ambient temperature of +70°C (no load derating required up to +70°C). This products finds many applications in distributed power systems where a voltage conversion at the point of load is required. All models are fully line and load regulated and maintain specified accuracy over the whole wide input voltage ranges. Output voltage ripple and noise is <50mV pk-pk with an additional 2.2uF low ESR electrolyte capacitor is equipped to the output. These step-down regulators do not need a minimum load and are continuous short circuit protected. They draw an input current of 1mA at no load condition and 100µA typ. in stand-by mode (extern Remote ON/OFF control turned o ff). On 3.3VDC output voltage models the output voltage can be adjusted between 1.8 and 3.3VDC respective on the 5VDC output models between 3.0 and 5.0VDC. 1. 1 Block diagram: Fig.: 1.1 Block Diagram of TSI 10N Step-down Regulator 2. Standard Application: These regulators should be connected to a low impedance input voltage source. High inductive source impedance can affect the stability of the regulator. In applications where the input power is supplied over long input lines and full load is required it maybe necessary to use a capacitor on the input to ensure a proper start-up. This capacitor should be equipped as close as possible to the regulator (see figure 2.1; C1) to ensure a very high stability of the regulator. We recommend to use a high quality low Equivalent Series Resistor (ESR < 1.0Ω at 100kHz). The values are 100µF for the 5V input models and 33µF for the 12V and 24V input models. F1 = - +Vin +Vout 4 TSI 10N C1 C2 ON/OFF 100µF/26V 1 for 5V Input Models 33µF/35V for 12V and 24V Input Models GND V Adj. 5 22µF/35V Load + 2 3 Figure 2.1: Standard Application To add a fuse on the input would be recommendable to reduce the risk of fire. (See figure 2.1 fuse F1). The recommended input fuses values are: TSI 10N-0510 recommended fuse = 4A slow blow type TSI 10N-1211 recommended fuse = 3A slow blow type TSI 10N-24xx recommended fuse = 1A slow blow type Created by Traco Electronic AG Arp. page 1 of 4 pages Date of print out: 22.02.07 File: Application_Note_General_TSI10N_28-03-2003.doc 3. Remote ON/OFF Control: The Remote ON/OFF control is used to reduce the input current to a very low level if the output power of the regulator is not used (to keep the regulator in a stand-by mode). For ON/OFF control, a low current closure is between the Remote ON/OFF pin and Vin(–), and can be provided by a mechanical switch, an open-collector transistor or an optoisolator. Figure 3.1, 3.2 and 3.3 shows different possibilities to provide a low current closure. Note that Von/off is defined as the voltage at the Remote ON/OFF pin with respect to the Vin(–) pin. Ion/off is the current drawing from the Remote ON/OFF pin. Please be aware that the Remote ON/OFF output do not provide any current nor any voltage level. The maximum sink current at the ON/OFF terminal during a logic low signal is 100µA. The maximum leakage of the switch at the ON/OFF terminal is 50µA at Von/off = 3 to 5VDC. +Vin Ion/off +Vin Remote ON/OFF Ion/off Module + Remote ON/OFF +Vin Ion/off Module + Von/off - -Vin Table No. 3.4: Summarizes of logic levels and module states Logic State Module State Logic Low or switch closed Module OFF Logic High or switch open Module ON Module Von/off - -Vin Figure 3.2: Open-Collector Transistor Figure 3.1: Mechanical Switch Remote ON/OFF -Vin Figure 3.3: Optocoupler (Optoisolator) If the Remote ON/OFF pin left isolated (open) or supplied with a high logic level (3.0 to 5.0VDC), the converter is ON and performs within the specifications and when the Remote ON/OFF pin is shorted to Vin(–) or supplied with a low logic level (-0.3 to 1.2VDC) the converter is OFF. Table 3.4 summarizes the logic levels and module states. Table 3.5 summarizes the electrical specifications for the Remote ON/OFF pin and the switch for isolated closure positive-logic ON/OFF. In order to satisfy the requirements for the low-impedance state, the Table No. 3.5: Positive-Logic Remote ON/OFF closure must maintain a voltage less than the Parameter Symbol Min Max maximum logic-low on/off ON/OFF Voltage: voltage. The logic-high voltage Logic Low (Switch closed Î Module OFF) Von/off -0.3 VDC 1.2 VDC (V on/off) defines the maximum Logic High (Switch open Î Module ON) Von/off 3.0 VDC 5.0 VDC voltage to which the ON/OFF pin floats when the isolated closure is in the high-impedance state. The isolated closure must be rated to handle the logic-low current (Ion/off) during its low-impedance state and withstand the logic-high voltage (Von/off) during its high-impedance state. Avoid any voltage levels between 1.2VDC and 3.0VDC on the Remote ON/OFF pin with respect to Vin(–). +Vin +Vin Vcc (+) TTL GATE System ON/OFF Control Ion/off + Remote ON/OFF Ion/off Module + 4.7V Von/off - Module Von/off - -Vin Remote ON/OFF -Vin Figure 3.7: Level Control / Using Line Voltage Figure 3.6: Level Controlled / Using TTL Gate Figure 3.6 shows a level controlled ON/OFF control using a TTL Gate. An other example of a level control is shown in figure 3.7 using a line driven circuit. The Zener diode is sized to clamp Von/off below the maximum high voltage level, while the resistor limits the power dissipation in the Zener diode. 3. Over Current Protection: To provide a sufficient protection in fault conditions (like over load or short circuit) these regulators are equipped with an internal current limiting circuitry and can handle continuous over load or short circuit conditions. At the current limitation trigger point the units switches from voltage controlled to current control. The current limitation is auto recovery and will perform within the specifications as soon as the over load or short circuit condition disappear. Created by Traco Electronic AG Arp. page 2 of 4 pages Date of print out: 22.02.07 File: Application_Note_General_TSI10N_28-03-2003.doc 4. Reduction of Output Ripple and Noise value: A high quality low ESR electrolyte capacitor of 22µF/35V (see figure 2.1; C2) placed as near as possible and practicable across the load will provide the best ripple and noise performance. By adding a 100nF ceramic capacitor parallel to the capacitor C2 will reduce the noise (spikes). 5. Maximum Capacitive Load: The TSI 10N series has a limitation of maximum capacitive load which can be connected to the output because the TSI 10N may perform in current limiting mode during start-up which affects the ramp up of the output voltage and start-up time. For a reliable performance of the TSI 10N we recommend not to have a higher capacitive load than 3300µF in total. 6. Output Voltage Adjustment: The TSI 10N series output voltage can be adjusted either between 1.8 and 3.3VDC (TSI 10N-xx10) or 3.0 to 5.0VDC (TSI 10N-xx11) by adding the resistor VR1 between VAdj pin and +Vout pin. See figure 6.1. The value for resistor VR1 depends on the requested output voltage value and can be calculated according to following formula: VR1 = (Rx • 1200) • (Vout - 1.195) = [Ω] (Rx • 1.195) - (1200 • (Vout • 1.195)) Rx = 2130Ω Î TSI 10N-xx10 Rx = 3840Ω Î TSI 10N-xx11 + = - +Vin +Vout 4 TSI 10N C1 ON/OFF 1 100µF/26V for 5V Input Models 33µF/35V for 12V and 24V Input Models GND 3 V Adj. VR1 5 C2 22µF/35V Load 2 Figure 6.1: Output Voltage Adjustment 7. Thermal Consideration: A lot of different conditions may affect the thermal performance of the TSI 10N regulator such as location, airflow around and over the TSI 10N regulator and spacing available around the TSI 10N regulator. To avoid any damage on the equipped components (exceeding the maximum temperature ratings of the components used on the TSI 10N regulator) the operating ambient temperature must be kept below +70°C. See figure 7.1 to find the point for the operating ambient temperature measurements. Figure 7.1: Test point for operating ambient temperature measurements The derating curves (see figure 7.2) are determinate from measurements obtained in an experimental apparatus. Figure 7.2: Derating curves Created by Traco Electronic AG Arp. page 3 of 4 pages Date of print out: 22.02.07 File: Application_Note_General_TSI10N_28-03-2003.doc 8. Outline Dimensions in mm (inches): 20.2 (+1.0 / -0.5) [0.795 (+0.04 / -0.02)] C/L 3.5 ±1.5 [0.138 ±0.06] 5 0.5 [0.02] 5.0 ±0.5 4.2 typ. [0.165 typ.] [0.945 max] 21.5 +1.0/-0.5 1 [0.846 +0.04/-0.02] 24.0 max 2.5 typ. [0.1 typ.] 8.3 max [0.327 max.] 0.8 [0.03] 0.25 [0.01] PINOUT Pin Description 1 Remote ON/OFF 2 +V Input (Vcc) -V Input 3 (GND) -V Output 4 +V Output 5 VAdj. Vout adjustment 2.54 2.54 2.54 2.54 [0.197 ±0.02] [0.1] [0.1] [0.1] [0.1] 8. Physical Characteristics: Vibration: 5 to 10Hz amplitude kept constant 10mm pk-pk 10 to 55Hz acceleration kept constant at 2G Shock: 20G max 11ms Weight: 8.6g (0.019lb.) Soldering 235°C max for 10 seconds Temperature: 455°F max for 10 seconds Created by Traco Electronic AG Arp. page 4 of 4 pages Date of print out: 22.02.07 File: Application_Note_General_TSI10N_28-03-2003.doc