MAX1259MJE Maxim Integrated, MAX1259MJE Datasheet - Page 5

• Manufacturer Part Number: MAX1259MJE
• Description: Battery Management
• Manufacturer: Maxim Integrated
• Series: MAX1259r

Specifications of MAX1259MJE

• Output Voltage: 3 V
• Output Current: 0.1 mA (Max)
• Operating Supply Voltage: 4.5 V to 5.5 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Package / Case: CDIP N
• Mounting Style: Through Hole

Figure 2 shows a typical application for the MAX1259.
CMOS RAM is powered from V
switchover circuit compares V
and connects V
Switchover occurs when V
falls, and when V
V
switching if V
equal to the battery voltage. Low-loss switches guaran-
tee an input-to-output differential of only 200mV, while
supplying 250mA from the primary power supply or
15mA from the battery.
Figure 1. Power-Down/Power-Up Conditions
Figure 2. Typical Application Circuit
CC
V
CC
rises. This hysteresis prevents repeated, rapid
15, 16
2
V
V
BATT
CCI
MAX1259
CC
CCO
GND
Battery Switchover and V
_______________________________________________________________________________________
7, 8
falls very slowly or remains nearly
CC
V
CCO
PF
to whichever is higher.
+4.25V
Detailed Description
is 60mV greater than V
V
+3V
CCI
12, 13
PF
11
CURRENT
BATTERY
CC
NMI
RAM1
μP
CC
equals V
t
PF
t
F
RAM2
to the V
CCO
RAM16
CE0
. The battery
BATT
CE1
ADDRESS
DECODE
BATT
BATT
as V
input,
CE15
CCO
CC
as
Note: With adequate filtering, the MAX1259 need only
supply the average current drawn by the CMOS RAM.
Many RAM data sheets specify a 75mA maximum sup-
ply current, but this peak current spike lasts only 100ns.
If the sum of the peak currents is greater than 250mA, a
capacitor placed on the V
high instantaneous current, while V
ply the average current, which is much less.
The MAX1259 operates with battery voltages from 2.5V
to 3.7V. High-value capacitors—either standard elec-
trolytic or farad-sized, double-layer capacitors—can
also be used for short-term memory backup (Figure 3).
Figure 3. Using a MAXCAP as a Backup Battery
6.2kΩ
NOTE: LARGE VALUE CAPACITORS, SUCH AS A 0.22F MAXCAP,
3kΩ
V
CC
MAY BE USED FOR SHORT-TERM MEMORY BACKUP.
MAXCAP
0.22F
2N3904
Battery Manager
t
R
15, 16
2
t
REC
V
V
BATT
CCI
CCO
MAX1259
GND
output can supply the
7, 8
CCO
V
CC0
need only sup-
12, 13
TO RAM
5