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PTB48540C Datasheet(PDF) 7 Page - Texas Instruments |
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PTB48540C Datasheet(HTML) 7 Page - Texas Instruments |
7 / 12 page Application Notes For technical support and further information visit http://power.ti.com Table 2-2 DC/DC CONVERTER ADJUSTMENT RESISTOR VALUES Series Pt # PTB48540B PTB48540A PTB48540C Vo(nom) 3.3 V 5 V 12 V Va(req’d) 2.95 (90.0)k Ω 3.0 (146.0)k Ω 3.05 (223.0)k Ω 3.1 (340.0)k Ω 3.15 (534.0)k Ω 3.2 (923.0)k Ω 3.25 (2090.0)k Ω 3.3 3.35 1190.0k Ω 3.4 501.0k Ω 3.45 272.0k Ω 3.5 157.0k Ω 3.55 88.4k Ω 3.6 42.5k Ω 3.65 9.7k Ω • 4.5 (258.0)k Ω 4.6 (364.0)k Ω 4.7 (541.0)k Ω 4.8 (895.0)k Ω 4.9 (1960.0)k Ω 5.0 5.1 578.0k Ω 5.2 234.0k Ω 5.3 119.0k Ω 5.4 62.1k Ω 5.5 27.7k Ω • 10.8 (399.0)k Ω 11.0 (499.0)k Ω 11.5 (1110.0)k Ω 12.0 12.5 87.8k Ω 13.0 18.9k Ω 13.2 7.5k Ω R 1 = (Blue) R 2 = Black PTB48540 Series Adjusting the Output Voltage of the PTB48540 Series of Power Over Ethernet Modules The set-point output voltage of the PTB48540 series of PoE modules may be adjusted (trimmed) by up to ±10 %. This is accomplished with the addition of a single exter- nal resistor. For the input voltage range specified in the data sheet, Table 2-1 gives the allowable adjustment range for each model as Vo (min) and Vo (max). Adjust Up: An increase in the output voltage is obtained by adding a resistor, R2 between pin 2 (Vout Adj), and pin 1 (–Vout). Adjust Down: Add a resistor (R1), between pin 2 (Vout Adj) and pin 3 (+Vout). Refer to Figure 2-1 and Table 2-2 for both the placement and value of the required resistor, (R1) or R2. The values of (R1) [adjust down], and R2 [adjust up], can also be calculated using the following formulas. (R1) = 56.2 (Va – 1.225) – Rs k Ω Vo – Va R2 = 68.845 – Rs k Ω Va – Vo Where, Vo = Original output voltage Va = Adjusted output voltage Rs = Internal resistance (Table 2-1) Notes: 1. Use only a single 1 % resistor in either the (R1) or R2 location. Place the resistor as close to the module as possible. 2. Never connect capacitors to Vo adjust. Any capacitance added to the Vo adjust control pin will affect the stability of the module. 3. The output power is limited to 10 W. If the output voltage is increased, the maximum load current must be derated according to the following equation. Io(max) = 10 Va In any instance, the load current must not exceed the converter’s rated current (See Table 2-1). Table 2-1 DC/DC CONVERTER ADJUSTMENT PARAMETERS Series Pt # PTB48540B PTB48540A PTB48540C Rated Current 3 3 A 2 A 0.85 A Vo(nom) 3.3 V 5 V 12 V Vo(min) 2.95 V 4.5 V 10.8 V Vo(max) 3.65 V 5.5 V 13.2 V Rs (k Ω Ω Ω Ω Ω) 187 110 49.9 +V OUT V OUT Adj –V OUT L O A D (R 1) Adjust Dn R 2 Adjust Up 1 2 3 PTB48540 Figure 2-1; Adjust Resistor Placement Not Recommended for New Designs |
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