Using the TPS2420, TPS2421-1 and TPS2421-2 User's Guide Literature Number: SLUU343 January 2009
User's Guide SLUU343 – January 2009 TPS2420 Hot Swap Controller System Test Board This user’s guide describes the setup and operation of the TPS2420 system test board. 1 Introduction This user’s guide describes the features of the TPS242X EVM. The TPS242X schematic, layout and List of Materials are provided as well as a setup and getting started. 2 Description The EVM is a 3 V to 18 V module using the TPS2420/21 hot swap controller with integrated MOSFET.
Block Diagram www.ti.com 2.2 Features • • • • • • • • • • • 3 3-V to 18-V Operation Controlled Inrush Current Fast Circuit Breaker Control Hardware Programmable – Operating Current – Fault Current – Fault Timer to Avoid Nuisance Tripping – Latch Off or Retry (TPS2420 is pin selectable, TPS2421-1 is latch-off only and TPS2421-2 is re-try only.) LED status display A Slide Switch Controls the ENABLE Signal.
Schematic 4 www.ti.com Schematic Figure 2.
List of Materials www.ti.com 5 List of Materials This is the List of Material for the TPS242X EVM Table 1. List of Materials COUNT REF DES DESCRIPTION PART NUMBER MFR 2 C1, C3 Capacitor, ceramic, 0.1 µF, 603 STD muRata 2 C2, C6 Capacitor, ceramic, 0.1 µF, 603 STD muRata 1 C4 Capacitor, ceramic, 10V , 0.56 µF, 805 STD muRata 1 C5 Capacitor, ceramic, 25 V, 1 µF, 1206 STD muRata 1 D1 Diode, LED, red, 20 mA, 0.9 mcd, 0.068 x 0.
Board Outline 6 www.ti.com Board Outline Figure 3. Board Outline (top) Figure 4.
Board Outline www.ti.com 6.1 Test Points Test Points TP14, TP15, TP16, TP17, are not installed. These are placed on the board unmarked near Load and Load Return. This is a user option to hardwire additional capacitors, etc to the output. Table 2. Test Points 6.2 TEST POINT NAME TP1 VIN TP2 4.3 V REF DESCRIPTION Input voltage power supply $0.
Equipment 6.4 www.ti.com Switches 6.4.1 Enable Switch S1 The Enable slide switch turns on the hot plug controller to ramp the output voltage. When the switch is off, the output is off. 6.5 Indicators • • Green LED Indicator for Power Good (PG) Red LED Indicator for FAULT (FLT) 7 Equipment 7.1 Equipment Needed 7.1.1 6.1.1 Voltage Source The input voltage source, VIN is a 20-V variable dc source at 10 A. 7.1.2 6.1.3 Oscilloscope A digital oscilloscope can be used to monitor the test points.
Getting Started (example) www.ti.com 8 Getting Started (example) 8.1 Equipment Connections Reference Figure 5 for equipment connections. • Input power supply positive voltage to J1 and negative voltage to GND, J2. Connectors J1 and J2 can accept #6 ring or spade lugs. • RC load at J4 and the load return at J5. The example here uses 220 µF, 15 Ω. • Scope to current probe to measure the load current. • Scope the VOUT - TP8, EN - TP3, PG - TP5.
Getting Started (example) 8.3 www.ti.com Test Results Observe waveforms similar to Figure 6. • The current to the load is not constant but increases after the initial inrush. Current is low initially because the voltage across the internal MOSFET is initially at its highest level and the controller is power limiting the MOSFET. VPASS = VIN - VOUT PTPS 2420 = VPASS ´ IOUT • • • Although the current limit, IFLT, is set to 4 A, the start up current never goes above 2.2 A because of the power limiting.
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