LT1307CS8#PBF Linear Technology, LT1307CS8#PBF Datasheet - Page 13

• Manufacturer Part Number: LT1307CS8#PBF
• Description: IC DC/DC CONV SINGLE CELL 8-SOIC
• Manufacturer: Linear Technology
• Type: Step-Up (Boost)r

Specifications of LT1307CS8#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V
• Current - Output: 100mA
• Frequency - Switching: 600kHz
• Voltage - Input: 1 ~ 5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Primary Input Voltage: 5V
• No. Of Outputs: 1
• Output Voltage: 28V
• Output Current: 100mA
• No. Of Pins: 8
• Operating Temperature Range: 0°C To +70°C
• Msl: MSL 1 - Unlimited
• Switching Frequency Max: 600kHz
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
tions where small size is not critical, Panasonic HFQ series
aluminum electrolytic capacitors have been found to per-
form well.
Table 2. Vendor Telephone Numbers
VENDOR
Coilcraft
Marcon
Murata-Erie
Sumida
Tokin
AVX
Sprague
Coiltronics
Diodes
Most of the application circuits on this data sheet specify
the Motorola MBR0520L surface mount Schottky diode.
This 0.5A, low drop diode complements the LT1307 quite
well. In lower current applications, a 1N4148 can be used,
although efficiency will suffer due to the higher forward
drop. This effect is particularly noticeable at low output
voltages. For higher voltage output applications, such as
LCD bias generators, the extra drop is a small percentage
of the output voltage so the efficiency penalty is small. The
low cost of the 1N4148 makes it attractive wherever it can
be used. In through hole applications the 1N5818 is the all
around best choice.
SHUTDOWN PIN
The LT1307 has a Shutdown pin (SHDN) that must be
grounded to shut the device down or tied to a voltage equal
or greater than V
shown in Figure 13.
Note that allowing SHDN to float turns on both the start-
up current (Q2) and the shutdown current (Q3) for V
2V
and behaves erratically. SHDN voltage above V
lowed. This merely reverse-biases Q3’s base emitter junc-
tion, a benign condition.
BE
. The LT1307 doesn’t know what to do in this situation
IN
Inductors, Capacitors
U
to operate. The shutdown circuit is
COMPONENTS
Capacitors
Capacitors
Capacitors
Capacitors
Inductors
Inductors
Inductors
U
W
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
U
TELEPHONE
IN
is al-
IN
>
LOW-BATTERY DETECTOR
The LT1307’s low-battery detector is a simple PNP input
gain stage with an open collector NPN output. The nega-
tive input of the gain stage is tied internally to a 200mV
ment as a low-battery detector is straightforward. Figure
14 details hookup. R1 and R2 need only be low enough in
value so that the bias current of the LBI pin doesn’t cause
large errors. For R2, 100k is adequate. The 200mV refer-
ence can also be accessed as shown in Figure 15.
5% reference. The positive input is the LBI pin. Arrange-
Figure 14. Setting Low-Battery Detector Trip Point
R1
R2
100k
SHDN
Figure 15. Accessing 200mV Reference
200mV
V
LBI
REF
2N3906
Figure 13. Shutdown Circuit
GND
200mV
INTERNAL
REFERENCE
+
–
10k
V
IN
Q1
+
R2
400k
200k
200k
10 F
LT1307/LT1307B
LT1307
V
IN
LBO
1307 F14
Q3
Q2
SHUTDOWN
CURRENT
START-UP
CURRENT
1307 F13
LBO
LBI
3.3V
LT1307
GND
V
1M
IN
R1 =
1307 F15
V
TO PROCESSOR
LB
– 200mV
2 A
13
1307fa