LT1073CN8 Linear Technology, LT1073CN8 Datasheet - Page 6

• Manufacturer Part Number: LT1073CN8
• Description: IC DC/DC CONVERTER ADJSTBL 8-DIP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Step-Up (Boost), Invertingr

Specifications of LT1073CN8

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adjustable
• Current - Output: 400mA
• Frequency - Switching: 19kHz
• Voltage - Input: 1 ~ 30 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Power - Output: 500mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
LT1073
Table 1. Component Selection for Step-Up Converters
G = GOWANDA
Measuring Input Current at Zero or Light Load
Obtaining meaningful numbers for quiescent current and
efficiency at low output current involves understanding
how the LT1073 operates. At very low or zero load current,
the device is idling for seconds at a time. When the output
voltage falls enough to trip the comparator, the power
switch comes on for a few cycles until the output voltage
rises sufficiently to overcome the comparator hysteresis.
When the power switch is on, inductor current builds up
to hundreds of milliamperes. Ordinary digital multimeters
are not capable of measuring average current because of
bandwidth and dynamic range limitations. A different
approach is required to measure the 100 A off-state and
500mA on-state currents of the circuit.
Quiescent current can be accurately measured using the
circuit in Figure 1. V
6
VOLTAGE (V)
1.55-1.25
1.30-1.05
1.55-1.25
1.30-1.05
3.1-2.1
3.1-2.1
3.3-2.5
3.1-2.1
3.1-2.1
3.3-2.5
4.5-5.5
4.5-5.5
4.5-5.5
INPUT
V
SET
Figure 1. Test Circuit Measures No-Load
Quiescent Current of LT1073 Converter
Single Alkaline
Single Alkaline
Single Ni-Cad
Single Ni-Cad
–
+
Two Alkaline
Two Alkaline
Two Alkaline
Two Alkaline
TTL Supply
TTL Supply
TTL Supply
BATTERY
LTC1050
Lithium
Lithium
TYPE
12V
U
SET
*NONPOLARIZED
is set to the input voltage of the
V1
U
100
VOLTAGE (V)
1 F*
1M
1000 F
OUTPUT
12
12
12
12
12
24
3
5
V2
3
5
5
5
5
+
W
CURRENT (MIN)
CIRCUIT
LT1073
OUTPUT
100mA
60mA
20mA
30mA
10mA
80mA
25mA
25mA
30mA
90mA
22mA
35mA
1073 F01
5mA
U
CB = CADDELL-BURNS
VALUE ( H)
INDUCTOR
1000
180
180
120
470
150
120
470
150
220
220
LT1073. The circuit must be “booted” by shorting V2 to
V
nect the short. Input voltage is V2 and average input
current can be calculated by this formula:
Inductor Selection
A DC/DC converter operates by storing energy as mag-
netic flux, in an inductor core and then switching this
energy into the load. Since it is flux, not charge, that is
stored, the output voltage can be higher, lower, or oppo-
site in polarity to the input voltage by choosing an appro-
priate switching topology. To operate as an efficient energy
transfer element, the inductor must fulfill three require-
ments. First, the inductance must be low enough for the
inductor to store adequate energy under the worst-case
condition of minimum input voltage and switch ON time.
The inductance must also be high enough so that maxi-
mum current ratings of the LT1073 and inductor are not
exceeded at the other worst-case condition of maximum
input voltage and ON time. Additionally, the inductor core
must be able to store the required flux, i.e., it must not
saturate. At power levels generally encountered with
LT1073-based designs, small axial-lead units with
82
82
SET
I
IN
. After the LT1073 output voltage has settled, discon-
V
100
G GA10-822K, CB 7300-12
G GA10-183K, CB 7300-16
G GA10-822K, CB 7300-12
G GA10-183K, CB 7300-16
G GA10-123K, CB 7300-14
G GA10-473K, CB 7300-21
G GA40-153K, CB 6860-15
G GA10-123K, CB 7300-14
G GA10-473K, CB 7300-21
G GA10-153K, CB 7300-15
G GA40-223K, CB 6860-17
G GA10-104K, CB 7300-25
G GA40-223K, CB 6860-17
2
–
V
PART NUMBER
1
INDUCTOR
CAPACITOR
VALUE ( F)
*Add 68 from I
150
100
470
150
470
220
470
100
150
220
100
47
22
LIM
NOTES
*
*
*
*
*
*
to V
IN