This inverting regulator is a compact, high power, extended input voltage range

“Positive to negative DC/DC conversion (negative output) is widely used in LCD devices, OLED displays, audio amplifiers, industrial equipment, measurement tools, test systems, LED drivers, and battery chargers. In all of these applications, inverting converters must be compact, support high power, and accommodate extended input voltage ranges. The LTC7149 meets all of these requirements. Its integrated 4A switch and wide input voltage range of 3.4V to 60V meet and exceed the requirements of most demanding applications, including those in automotive environments.

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Positive to negative DC/DC conversion (negative output) is widely used in LCD devices, OLED displays, audio amplifiers, industrial equipment, measurement tools, test systems, LED drivers, and battery chargers. In all of these applications, inverting converters must be compact, support high power, and accommodate extended input voltage ranges. The LTC7149 meets all of these requirements. Its integrated 4A switch and wide input voltage range of 3.4V to 60V meet and exceed the requirements of most demanding applications, including those in automotive environments.

Circuit Description and Function

Figure 1 shows a positive-to-negative converter based on the LTC7149. This solution provides a C10V/2A output from a 12V input voltage (eg, an automotive power rail). The power chain components are selected for a nominal 12V input, but with appropriate derating, the input voltage for this application can be as low as 4V or as high as 50V.

Figure 1: LTC7149 Positive-to-Negative Converter (V_IN: 4V ~ 50V, V_OUT: C10V/2A)

In automotive applications, the LTC7149’s ability to handle high voltage inputs eliminates the need for expensive voltage suppressors. Very low minimum input voltage keeps sensitive systems operating even in cold crank conditions. Guidelines for calculating voltage and current stress on components surrounding the LTC7149 can be found in the LTC7149 data sheet. Figure 2 shows an example of output current derating for input voltages below 12V.

Figure 2: Output Current Derating vs. Input Voltage (for the circuit of Figure 1)

The circuit of Figure 1 uses external loop compensation. As shown in Figure 3, connect ITH to INTV_CC Internal compensation is allowed. Connect MODE/SYNC to GND to enable Burst Mode^®) operate. If desired, a sync pulse referenced to GND can be applied to this pin. The efficiency of this solution reached 94%.

Voltage Controlled Variable Negative Output Circuit

Dynamically changing negative bias is required for many applications, including LCDs, OLED monitors, and test equipment systems. The LTC7149 has features designed to simplify this task.

Figure 3 shows a negative voltage supply where the negative output is controlled by a positive signal voltage. A positive control voltage referenced to GND is applied to V_OUTSNS pin. In Figure 3, this is V in the 0V to 5V range_CTRL. The resulting negative output voltage V_OUTC It is determined by the following formula:

V_OUTC = C50μA • R_SET +V_CTRL

Figure 3: With variable _VOUTC Positive to Negative Converter (from C5V to C10V)

low pass filter R_F/C_F Provides noise suppression. V_OUTSNS The pin must not be floating under any circumstances, a voltage potential must always be present on the pin. If this requirement cannot be met (e.g. during system testing), resistor R should be installed_P.

Figure 4 shows that V_OUTC with V_CTRL The functional relationship curve of . Figure 5 illustrates the broad application potential of this approach, since V_CTRL The voltage is shaped into a sine wave with an amplitude of 2.5V.

Figure 4: As V_CTRL Variable negative output V of a linear function of_OUT.

Figure 5: Variable Negative Output V_OUTC follow V_CTRL sine waveform on .

in conclusion

The LTC7149 is a high efficiency 50V, 4A synchronous monolithic regulator for negative output supplies that combines wide input and output voltage ranges with integrated switching transistors to simplify converter design. The solutions and circuits discussed in this Design Essentials assist in implementing this regulator in automotive and industrial applications, Display and monitor systems.