LM2687 LM2687 Low Noise Regulated Switched Capacitor Voltage Inverter Literature Number: SNVS060D
LM2687 Low Noise Regulated Switched Capacitor Voltage Inverter General Description Features The LM2687 CMOS Negative Regulated Switched Capacitor Voltage Inverter delivers a very low noise adjustable output for an input voltage in the range of +2.7V to +5.5V. Four low cost capacitors are used in this circuit to provide up to 10mA of output current. The regulated output for the LM2687 is adjustable between −1.5V and −5.2V.
LM2687 Ordering Information for MSOP Package Device Order Number Package Number Package Marking* LM2687MM MUA08A S12A Tape and Reel (1000 units/reel) LM2687MMX MUA08A S12A Tape and Reel (3500 units/reel) Supplies As Ordering Information for LLP Package Device Order Number Package Number Package Marking* LM2687LD LDA08A L050B Tape and Reel (1000 units/reel) LM2687LDX LDA08A L050B Tape and Reel (3500 units/reel) Supplies As Note: * The small physical sizes of the MSOP-8 and LLP-8 pack
TJMAX (Note 3) (Note 1) θJA (Note 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VIN to GND or GND to OUT) 150˚C 250˚C/W Operating Input Voltage Range 2.7V to 5.5V Operating Output Current Range Operating Ambient + 5.8V Temp. Range (GND − 0.3V) to (VIN + 0.3V) SD VNEG and VOUT Continuous Output Current 10mA VOUT Short-Circuit Duration to GND (Note 2) 1 sec.
LM2687 10118021 FIGURE 1. Standard Application Circuit for Minimum Capacitance Values 10118022 FIGURE 2. Standard Application Circuit for Low Output Noise www.national.
Unless otherwise specified, TA = 25˚C, VOUT = −2.5V. Output Voltage vs. Output Current Figure 2 Output Voltage vs. Output Current Figure 1 10118005 10118004 Output Voltage vs. Input Voltage Maximum Output Current vs. Input Voltage 10118006 10118007 Maximum VNEG Current vs. Input Voltage No Load Supply Current vs. Input Voltage 10118008 10118009 5 www.national.
LM2687 Typical Performance Characteristics Unless otherwise specified, TA = 25˚C, VOUT = −2.5V. (Continued) Start-Up Time vs. Input Voltage Figure 1 Switching Frequency vs. Input Voltage 10118010 10118011 Start-Up from Shutdown (no load) Figure 2 Output Ripple Figure 1 10118013 10118012 Output Ripple Figure 2 Line Transient Response 10118017 10118014 www.national.
LM2687 Typical Performance Characteristics Unless otherwise specified, TA = 25˚C, VOUT = −2.5V. (Continued) Load Transient Response VFB vs. Temperature 10118018 10118015 Output Noise Spectrum Figure 1 Output Noise Spectrum Figure 2 10118024 10118023 10118003 FIGURE 3. Functional Block Diagram 7 www.national.
LM2687 Device Description The LM2687 is an inverting, regulated charge-pump power converter. It features low noise, small physical size, and is simple to use. It is an ideal solution for biasing GaAsFET devices such as power amplifier modules found in portable devices and cellular phones. A switched capacitor charge-pump circuit is used to invert the input voltage VIN to its corresponding negative value which is seen at VNEG. This voltage is regulated by a low dropout linear regulator at VOUT (Figure 3).
LM2687 Physical Dimensions inches (millimeters) unless otherwise noted MSOP-8 Package 8-Lead Mini SO-8 (MM) For Ordering, Refer to Ordering Information Table NS Package Number MUA08A 9 www.national.
LM2687 Low Noise Regulated Switched Capacitor Voltage Inverter Physical Dimensions inches (millimeters) unless otherwise noted (Continued) LLP-8 Package 8-Lead Leadless Leadframe Package (LD) For Ordering, Refer to Ordering Information Table NS Package Number LDA08A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.
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