LT1239CS Linear Technology, LT1239CS Datasheet - Page 11

• 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

APPLICATIONS
backup batteries have been completely discharged. Once the
backup batteries are charged the power in regulator 1 drops
significantly. The power in regulator 2 when regulator 2 is
providing power to the memory will be equal to:
I
monitoring circuitry.
The power in the comparator when the comparator is provid-
ing power to the memory will be equal to:
I
monitoring circuitry. Comparator Output Saturation Voltage
vs Output Current can be found in the Typical Performance
Characteristics.
OUT
OUT
(V
Example: (6.8V – 4.85V) 30mA = 58.5mW
(V
Example: (V
is the current needed to power the memory and power
SAT
BACKUPBATTERY
is the current needed to power the memory and power
I
OUT
SAT
)
U
I
– 4.85V) I
LOAD
MAIN
BATTERY
PACK
INFORMATION
) = (0.15V 30mA) = 4.5mW
U
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Figure 5. Adding a Protection Resistor for Lithium-Ion Charger
+
OUT
V
1
W
R4 >
IN 1
GND
MAX CHARGE CURRENT
LT1239
V1 – V2
U
E/A (0UT)
E/A (IN)
OUT 1
I
MON1
ADJ
Note that power for memory will be supplied by either
regulator 2 or the comparator. The power in the error
amplifier when the cells are unequalized will be equal to:
This component goes to zero when the cell voltages are
equalized.
The thermal resistance of the LT1239 is 120 C/W when
the device is mounted to a PC board with at least one
ground or power plane. The junction temperature rise will
be equal to the total power in the device multiplied by
120 C/W or (P
the junction temperature rise will be (300mW 120 C/W)
= 36 C. Given that the thermal limit temperature is ap-
proximately 100 C, this allows for a maximum ambient
temperature of roughly 60 C before the device thermal
limits. This temperature is near the maximum ambient
allowed for most battery types.
*R4
300pF
C1
Example: (6.8V/2) 3mA = 10.2mW
V
BACKUPBATTERY
*THIS RESISTOR IS REQUIRED
V
BY SOME SAFETY AGENCIES.
2
R3
604k
R2
69.8k
R1
681k
TOTAL
+
/2
10 F
120 C/W). For 300mW dissipation
3mA
3.4V Li-Ion
CELL
3.4V Li-Ion
CELL
LT1239 • F05
LT1239
11