LM2574 Micrel, Inc.
M9999-072805 4 July 2005
Electrical Characteristics
Symbol Parameter Condition Min Typ Max Units
Device Parameters, Adjustable Regulator
I
B
Feedback Bias Current V
OUT
= 5V 50 100 nA
500 nA
Device Parameters, Fixed and Adjustable Regulators
f
o
Oscillator Frequency Note 8 47 52 58 kHz
42 63 kHz
V
SAT
Saturation Voltage I
OUT
= 0.5A
(4)
0.8 1.2 V
1.4 V
DC Max Duty Cycle (ON)
Note 5 93 98 %
I
CL
Current Limit Peak Current, t
ON
≤ 3µs
(4)
0.7 1.0 1.6 A
0.65 1.8
I
L
Output Leakage Current V
IN
, Note 6, Output = 0V 2 mA
Note 6, Output = –1V 7.5 30
I
Q
Quiescent Current Note 6 5 10 mA
I
STBY
Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50 200 µA
θ
JA
Thermal Resistance N Package, Junction to Ambient
(7)
85 °C/W
On/Off Control, Fixed and Adjustable Regulators Test Circuit
Figures 2, 3
V
IH
ON/OFF Input Level V
OUT
= 0V 2.2 1.4 V
2.4 V
V
IL
ON/OFF Input Level V
OUT
= 5V 1.2 1.0 V
0.8 V
I
IH
ON/OFF Logic Current ON/OFF = 5V (OFF) 4 30 µA
I
IL
ON/OFF Logic Current ON/OFF = 0V (ON) 0.01 10 µA
Notes:
4. Output (pin 2) sourcing current. No diode, inductor, or capacitor connected to input.
5. Feedback (pin 4) removed from output and connected to 0V.
6. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.
7. Junction-to-ambient thermal resistance with approximately 1 square inches of PC board copper surrounding the leads.
Test Circuit
V
IN
PWR
GND
SIG
GND
ON/
OFF
OUT
FB
LM2574
(adjustable)
C
IN
22µF
11DQ06
C
OU T
220µF
330µH
3.09k
1k
Figure 2. Adjustable Regulator Test Circuit
V
IN
P W R
GND
SI G
GND
ON/
OF F
OUT
FB
LM2574–
3.3, 5, 12
C
IN
22µF
11DQ06
C
OU T
220µF
330µH
Figure 3. Fixed Regulator Test Circuit
