13
L T 1111
1111fd
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
Table 2. Inductor Manufacturers
MANUFACTURER PART NUMBERS
Coiltronics Incorporated CTX100-4 Series
6000 Park of Commerce Blvd. Surface Mount
Boca Raton, FL 33487
407-241-7876
Toko America Incorporated Type 8RBS
1250 Feehanville Drive
Mount Prospect, IL 60056
312-297-0070
Sumida Electric Co. USA CD54
708-956-0666 CDR74
CDR105
Surface Mount
Using the Gain Block
The gain block (GB) on the LT1111 can be used as an error
amplifier, low-battery detector or linear post regulator.
The gain block itself is a very simple PNP input op amp with
an open collector NPN output. The negative input of the
gain block is tied internally to the 1.25V reference. The
positive input comes out on the SET pin.
Arrangement of the gain block as a low-battery detector
is straightforward. Figure 12 shows hookup. R1 and R2
need only be low enough in value so that the bias current
of the SET input does not cause large errors. 33k for R2
is adequate. R3 can be added to introduce a small amount
of hysteresis. This will cause the gain block to “snap”
when the trip point is reached. Values in the 1M to 10M
range are optimal. However, the addition of R3 will
change the trip point.
Table 3. Capacitor Manufacturers
MANUFACTURER PART NUMBERS
Sanyo Video Components OS-CON Series
1201 Sanyo Avenue
San Diego, CA 92073
619-661-6322
Nichicon America Corporation PL Series
927 East State Parkway
Schaumberg, IL 60173
708-843-7500
Sprague Electric Company 150D Solid Tantalums
Lower Main Street 550D Tantalex
Sanford, ME 04073
207-324-4140
Matsuo 267 Series
714-969-2491 Surface Mount
LT1111 • F12
V
BAT
R1
R2
1.25V
REF
SET
GND
IN
V
LT1111
47k
5V
TO
PROCESSOR
+
–
A0
R3
R1 =
V
LB
– 1.25V
35.1µA
V
LB
= BATTERY TRIP POINT
R2 = 33k
R3 = 1.6M
Figure 12. Setting Low-Battery Detector Trip Point
Table 1. Component Selection for Common Converters
INPUT OUTPUT OUTPUT CIRCUIT INDUCTOR INDUCTOR CAPACITOR
VOLTAGE VOLTAGE CURRENT (MIN) FIGURE VALUE PART NUMBER VALUE NOTES
2 to 3.1 5 90mA 4 15µH S CD75-750K 33µF*
2 to 3.1 5 10mA 4 47µH S CD54-470K, C CTX50-1 10µF
2 to 3.1 12 30mA 4 15µH S CD75-150K 22µF
2 to 3.1 12 10mA 4 47µH S CD54-470K, C CTX50-1 10µF
5 12 90mA 4 33µH S CD75-330K 22µF
5 12 30mA 4 47µH S CD75-470K, C CTX50-1 15µF
6.5 to 11 5 50mA 5 15µH S CD54-150K 47µF**
12 to 20 5 300mA 5 56µH S CD105-560K, C CTX50-4 47µF**
20 to 30 5 300mA 5 120µH S CD105-121K, C CTX100-4 47µF**
5 –5 75mA 6 56µH S CD75-560K, C CTX50-4 47µF
12 –5 250mA 6 120µH S CD105-121K, C CTX100-4 100µF**
S = Sumida
C = Coiltronics
* Add 47Ω from I
LIM
to V
IN
** Add 220Ω from I
LIM
to V
IN
