LT1239CS Linear Technology, LT1239CS Datasheet - Page 7

• Manufacturer Part Number: LT1239CS
• Description: IC BATT BACKUP MNGMNT SYS 16SOIC
• Manufacturer: Linear Technology

Specifications of LT1239CS

• Function: Back-Up Management
• Battery Type: Lithium-Ion (Li-Ion); Nickel-Metal Hydride (NiMH)
• Voltage - Supply: 7 V ~ 30 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

FUNCTIONAL DESCRIPTIO
Comparator: The output of the comparator is connected to
the output of regulator 2. This point provides power to
memory and power management circuitry. The compara-
tor looks at the main 5V power line and the output voltage
of regulator 2. If the main 5V line is up and regulating the
comparator output will pull up to 5V and supply power to
the memory from the main 5V regulator. If the main 5V
power line drops below 4.85V the comparator switches off
and regulator 2 will supply power to the memory from the
backup batteries. The comparator is powered from the raw
battery voltage at the input of regulator 1.
Error Amplifier: The Error Amplifier is used to equalize the
cell voltages of two lithium-ion cells connected in series.
The error amplifier is designed to source or sink 5mA.
APPLICATIONS
Device Overview
The LT1239 provides several functions needed for backup
battery management. It provides:
1. Battery Charging: The LT1239 can be set up to charge
2. Memory Power Control: The LT1239 provides power
BLOCK
lithium-ion or nickel cadmium batteries in either con-
stant voltage or constant current mode.
for the memory and includes automatic switchover
U
INPUT 1
DIAGRAM
U
14
SHDN1
3
U
REGULATOR
4
GND
1
2
INFORMATION
U
W
I
MON1
INPUT 2
15
16
1
10
OUT 1
ADJUST
W
U
E/A (IN)
LOW-BATTERY
DETECTOR
GROUND PINS 2, 4, 5 ARE TIED TO SUBSTRATE
U
7
IN
–
+
E/A
Low-Battery Detector: The low-battery detector circuit
acts as an undervoltage lockout. This circuit turns regula-
tor 2 and the error amplifier off if the backup battery
voltage drops below 5V. The low-battery detector circuit
will turn regulator 2 and the error amplifier back on when
the backup battery voltage rises above 5.3V. This circuit
has a quiescent current of approximately 3 A in the
undervoltage condition.
Regulator 2: Regulator 2 is used to regulate the voltage of
the backup batteries and isolate the backup batteries from
the main 5V line. This regulator will prevent reverse
current flow from the main 5V supply back into the backup
cells.
between the backup battery and the main 5V system
power. When the 5V system supply is up and running it
is used to power the memory, the regulator prevents
reverse current flow back into the backup battery.
Automatic switchover occurs when the 5V system
supply drops below 4.85V and the regulator then pro-
vides power to the memory from the backup cells.
Memory power is uniterruptable.
SHDN2
6
REGULATOR
GND
8
2
5
IN
E/A (OUT)
I
MON2
11
+
–
INPUT 1
COMP
OUT 2
12
POWER
SWITCH
13 5V
1239 BD
LT1239
IN
7