Datasheet LT1120A (Analog Devices) - 7

LT1120A
block DiagraM
REF 6 VIN 5 + 100k COMP OUT 7 – 4 V REF OUT 2.5V 2 FEEDBACK 120k 3 SHUTDOWN 1 GROUND 8 –INPUT 1120A BD01
applicaTions inForMaTion
The LT1120A is especially suited for micropower system
Reference
applications. For example, the comparator section of the Internal to the LT1120A is a 2.5V trimmed class B out- LT1120A may be used as a battery checker to provide an put reference. The reference was designed to be able indication of low battery. Another type of system applica- to source or sink current so it could be used in supply tion for the LT1120A would be to generate the equivalent splitting applications as well as a general purpose refer- of split supplies off of a single power input. The regu- ence for external circuitry. The design of the reference lator section provides regulated output voltage and the al ows it to source and sink typical y 4mA. The avail- reference, which can both source and sink current is then able source and sink current decreases as temperature an artificial system ground providing a split supply for increases. It is sometimes desirable to decrease the AC the system. output impedance by placing an output capacitor on Pin For many applications the comparator can be frequency 6. The reference in the LT1120A becomes unstable with compensated to operate as an amplifier. Compensation large capacitive loads placed directly on it. When using an values for various gains are given in the data sheet. The output capacitor, about 20Ω should be used to isolate the comparator gain is purposely low to make it easier to capacitor from the reference pin. This 20Ω resistor can be frequency compensate as an amplifier. The NPN output is placed directly in series with the capacitor or alternatively capable of sinking 10mA and can drive loads connected the reference line can have 20Ω placed in series with it to voltages in excess of the positive power supply. This and then a capacitor to ground. This is shown in Figure 1. is useful for driving switches or linear regulators off of a higher input voltage. 1120afb For more information www.linear.com/LT1120A 7 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Package Description Revision History Related Parts