LT1500IS-3/5 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LT1500IS-3/5' PDF : 16 Pages View PDF
LT1500/LT1501
APPLICATIONS INFORMATION
capacitors may require the capacitor to be larger. To
ensure proper reset of the soft start capacitor, an external
resistor must be connected in parallel with the capacitor.
The resistor value should be 470k or more.
Calculating Temperature Rise
For most applications, temperature rise in the IC will be
fairly low and will not be a problem. However, if load
currents are near the maximum allowed and ambient
temperatures are also high, a calculation should be done
to ensure that the maximum junction temperature of
100°C is not exceeded. The calculations must account for
power dissipation in the switch, the drive circuitry and the
sense resistor.
PTOTAL
=
(IOUT )2(RSW)(VOUT )(VOUT
(VIN )2
−
VIN )
( ) ( ) + IOUT VOUT − VIN
30
+
RSENSE IOUT • VOUT
(VIN ) 2
2
PTOTAL = total device power dissipation
RSW = switch resistance (0.72Ω max)
RSENSE = sense resistance (0.42Ω max)
With VIN = –2.2V, VOUT = 5V, IOUT = 150mA, an 8-pin SO
package and maximum ambient temperature of 85°C
(industrial range),
PTOTAL
=
(0.15)2(0.72)(5)(5
(2.2)2
−
2.2)
+
0.15(5 −
30
2.2)
+
0.42(0.15 •
(2.2)2
5)2
= 0.47 + 0.014 + 0.049 = 0.11W
The SO package has a thermal resistance of 120°C/W, so
maximum device temperature will be:
TJMAX = 85°C + 0.11W(120°C/W) = 98°C
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157**
(3.810 – 3.988)
14
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
2
34
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270)
BSC
SO8 0695
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