LM2636M/NOPB National Semiconductor, LM2636M/NOPB Datasheet - Page 9

• Manufacturer Part Number: LM2636M/NOPB
• Description: IC REG SYNCH BUCK 5-BIT 20-SOIC
• Manufacturer: National Semiconductor

Specifications of LM2636M/NOPB

• Applications: Power Supplies
• Current - Supply: 2.5mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM2636M; *LM2636M/NOPB; LM2636M

Applications Information
turned on. Whenever an over current condition is detected,
the high side switch is immediately turned off and the low
side switch turned on, until the next switching cycle comes.
The delay of 300 ns is to circumvent switching noise when
the MOSFET is first turned on.
DESIGN CONSIDERATIONS
Control Loop Compensation
A switching regulator should be properly compensated to
achieve a stable condition. For a synchronous buck regula-
tor that needs to meet stringent load transient requirement
such as a Pentium II MPU core voltage supply, a simple
2-pole-1-zero compensation network should suffice, such as
the one shown in Figure 4 (C
because the ESR zero of the typical output capacitors is low
enough to make the control-to-output transfer function a
single-pole-roll-off.
As an example, let us figure out the values of the compen-
sation network components in Figure 4. Assume the follow-
ing parameters: R = 20Ω, R
C = 7.5 mF, V
= 300 kHz. These parameters are based on the typical
application in Figure 1. Notice R
DC resistance and the on resistance of the MOSFETs.
FIGURE 4. Buck Converter from a Control Point of
IN
= 5V, V
m
L
View
= 2V and switching frequency
= 20 mΩ, R
1
L
, C
is the sum of the inductor
2
, R
C
1
= 9 mΩ, L = 2 µH,
and R
(Continued)
2
). This is
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