LM3524DN National Semiconductor, LM3524DN Datasheet - Page 17

• Manufacturer Part Number: LM3524DN
• Description: ENHANCED PWM CONTROLLER, 3524, DIP
• Manufacturer: National Semiconductor

Specifications of LM3524DN

• Frequency: 350kHz
• Power Dissipation Pd: 1W
• Digital Ic Case Style: DIP
• No. Of Pins: 16
• Operating Temperature Range: 0°C To +125°C
• Svhc: No SVHC (15-Dec-2010)
• Operating Temperature Max: 125°C
• Base Number: 3524
• Controller Type: PWM
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Typical Applications
THE STEP-UP SWITCHING REGULATOR
Figure 18 shows the basic circuit for a step-up switching
regulator. In this circuit Q1 is used as a switch to alternately
apply V
and energy is drawn from V
biased and I
Q1 opens, t
where D1 turns ON. The output current is now supplied
through L1, D1 to the load and any charge lost from C
during t
regulator, the current through L1 has a DC component plus
some ∆I
I
ON and OFF times.
Since ∆I
and neglecting V
The above equation shows the relationship between V
and duty cycle.
L
. Figure 19 shows the inductor’s current in relation to Q1’s
FIGURE 18. Basic Step-Up Switching Regulator
IN
ON
L
L
. ∆I
+ = ∆I
across inductor L1. During the time, t
is replenished. Here also, as in the step-down
o
OFF
L
is supplied from the charge stored in C
is again selected to be approximately 40% of
L
, voltage V1 will rise positively to the point
−, V
SAT
IN
FIGURE 19. Relation of Switch Timing to Inductor Current in Step-Up Regulator
and V
t
ON
= V
D1
IN
and stored in L1; D1 is reverse
o
t
OFF
− V
(Continued)
IN
t
OFF
,
ON
, Q1 is ON
00865023
o
. When
IN
, V
o
o
17
In calculating input current I
tor’s DC current, assume first 100% efficiency:
for η = 100%, P
OUT
= P
IN
IN(DC)
00865024
, which equals the induc-
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