FEATURES DESCRIPTIONS (CON.)
Output Voltage Adjustment (TRIM)
To increase or decrease the output voltage set point, connect an external resistor between the TRIM pin and either the SENSE(+) or
Figure 20: Circuit configuration for trim-up (increase output voltage)
If the external resistor is connected between the TRIM and SENSE (+) pins, the output voltage set point increases (Fig. 20). The external resistor value required to obtain a percentage of output voltage change △% is defined as:
⎡ | Vonom(1 + ∆) − Vref | ⎤ | |
Rtrim_up(∆) = ⎢ | ⎥10kΩ − 11kΩ | ||
Vref∆ | |||
⎣ | ⎦ |
where
Vonom = nominal Vout (3.3V or 1.8V) Vref = 1.225V
∆= trim expressed as decimal fraction, i.e. 10% is written as 0.1
Ex. When trim up to 1.9V from 1.8V Vonom = 1.8V
Vref = 1.225V
∆ =
Rtrim − up = (1.8⋅1.05556 −1.225) ⋅10KΩ
⇒1.225* 0.05556
−11KΩ = 88.18KΩ
Figure 21: Circuit configuration for trim-down (decrease output voltage)
If the external resistor is connected between the TRIM and SENSE
Rtrim_down(∆) = 10ΚΩ − 11kΩ
∆
where
Vonom = nominal Vout (3.3V or 1.8V)
∆= trim expressed as decimal fraction, i.e. 40% is written as 0.4
Ex. When trim down to 0.8V from 1.8V
Vonom = 1.8V
∆=
Rtrim − down = 0.555610K −11KΩ = 7KΩ
The output voltage can be increased by both the remote sense and the trim, however the maximum increase allowed is the larger of either the remote sense spec or the trim spec, not the sum of both.
When using remote sense and trim, the output voltage of the module is usually increased, which increases the power output of the module with the same output current.
Care should be taken to ensure that the maximum output power of the module remains at or below the maximum rated power.
Output voltage | Ω | ) |
| Resistor value ( k | |
1.5V | 49.00 |
|
1.2V | 19.00 |
|
1.0V | 11.50 |
|
0.9V | 9.0 |
|
0.8V | 7.0 |
|
Figure 22: Trim resistor value example for popular output voltages. Connect the resistor between the TRIM and SENSE (-) pins.
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