lm2637mx National Semiconductor Corporation, lm2637mx Datasheet
lm2637mx
Available stocks
Related parts for lm2637mx
lm2637mx Summary of contents
Page 1
... GTL+ bus an easy job. In minimum configuration, the two controllers default to 1.5V and 2.5V respectively. Pin Configuration M II ™ trademark of Cyrix Corporation a wholly owned subsidiary of National Semiconductor Corporation. Pentium is a trademark of Intel Corporation. ™ trademark of Advanced Micro Devices, Inc. © 2004 National Semiconductor Corporation Both linear controllers have under voltage latch-off ...
Page 2
Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications Junction Temperature Power Dissipation (Note 2) Electrical Characteristics 12V unless ...
Page 3
Electrical Characteristics 12V unless otherwise specified. Typicals and limits appearing in plain type apply for appearing in boldface type apply over the 0˚C to +70˚C range. Symbol Parameter B Error Amplifier Unity ...
Page 4
V = 12V 5 25˚C, Test Mode Symbol V 5-Bit DAC Output Voltages for Different VID Codes DACOUT www.national.com TABLE 1. 5-Bit DAC Output Voltage Table Parameter VID4:0 = 01111 VID4:0 ...
Page 5
Block Diagram 5 10084830 www.national.com ...
Page 6
Test Circuit Typical Applications FIGURE 2. Motherboard Power Supply for Pentium II Processor Core (1.3V - 2.8V, 14.2A), GTL+ Bus (1.5V, 4A), and Legacy I/O (2.5V, 0.3A). External sense resistor is used to provide both over-current limit and dynamic voltage ...
Page 7
Typical Applications (Continued) FIGURE 3. Motherboard Power Supply for Pentium II Processor Core (1.8V - 2.8V, 14.2A), GTL+ Bus (1.5V, 4A), and Legacy I/O (2.5V, 0.3A). High side FET is used to provide the current limit. 7 10084804 www.national.com ...
Page 8
Pin Description Pin Pin Name 1 LG Low side N-FET gate driver output. 2 PGND Ground for the two FET drivers of the switching section Supply for the FET gate drivers. Usually tied to +12V SNS2 ...
Page 9
Applications Information provides two levels of protection. The first turns off the high-side FET and turns on the low-side. The second pro- vides a gate signal that can be used to fire an external SCR. The PWM frequency is adjustable ...
Page 10
Applications Information happens, the error in the output voltage level is fed to the error amplifier. The output of the error amplifier is then compared with an internally generated PWM ramp signal and the result of the comparison is a ...
Page 11
Applications Information Notice however, that the r of the FET has a positive DS_ON temperature coefficient and it can increase by as much as 50% when heated up. Also the distribution of the r be fairly wide, a 1.25 to ...
Page 12
Applications Information The corresponding Bode plots are shown in Figure 7. Notice since the ESR zero frequency is so low that the phase doesn’t even go beyond −90˚. This makes the compensation easier to do. Since the DC gain and ...
Page 13
Applications Information FIGURE 8. Loop Bode Plots Linear Section — The linear section is designed for high control bandwidth operation. The phase margin and cutoff frequency depends on the external N-FET, output capacitors and their ESR rule of ...
Page 14
Applications Information may have to have a small output inductor to quickly supply current to the output capacitors when the load suddenly kicks in and to quickly stop supplying current when the load is suddenly removed. Multilayer ceramic (MLC) capacitors ...
Page 15
Applications Information Since the D of LM2637 is at 0%, the slew rate is therefore MIN −1.4 A/µs. So the approximate total recovery time will be 14A/(1.4 A/µ µs. Often times the power supply designer may have to ...
Page 16
Applications Information FIGURE 10. Dynamic Voltage Positioning by Using a Stand-Alone Resistor A possible drawback of the scheme in Figure 9 is slow transient recovery speed. Since the 5 kΩ resistor and the 0.1 µF capacitor have a large time ...
Page 17
Physical Dimensions inches (millimeters) unless otherwise noted National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and ...