Datasheet

MAX1758
Stand-Alone, Switch-Mode
Li+ Battery Charger with Internal 28V Switch
12
Maxim Integrated
CSS
LEVEL SHIFT
AND
GAIN OF 10
ON
CCV
RCS
Rx
R2
BDIV
TO
BATT
R
3Rx
+1
GMS
TO
BATT
ENABLE
GMI
MIN AND CLAMP
REF
VL
CCI
CCS
BST
PGND
HSD
LX
CSSN
CSSP
GMV
CS
BATT
ISETIN
ISETOUT
CELL
VADJ
CNTRL
LOGIC
CSI
LEVEL SHIFT
AND
GAIN OF 7
ON
ON
SUMMING
COMPARATOR
BLOCK
LEVEL
SHIFT
REF/2 =
ZERO
CURRENT
V/I MODE
TO REF
OSCILLATOR, SM, TIMERS
THERM CONTROL
TEST CIRCUITRY
R2 = R(2N -1)
WHERE
N = CELL NUMBER
Rx
REF/2
3Rx
9R R
R
DCIN
THM
5.4V
REGULATOR
INTERNAL
REFERENCE
DRIVER
+1
FASTCHG
FULLCHG
FAULT
TIMER 1
TIMER 2
GND
+1
MAX1758
Figure 3. MAX1758 Functional Diagram
Input Current Regulator
The total input current (from a wall cube or other DC
source) is the sum of system load current plus the bat-
tery-charging current. The input current regulator limits
the source current by reducing charging current when
input current exceeds the set input current limit. System
current will normally fluctuate as portions of the system
are powered up or put to sleep. Without input current
regulation, the input source must be able to supply the
maximum system load current plus the maximum
charger input current. By using the input current limiter,
the current capability of the AC wall adapter may be
lowered, reducing system cost.
Input current is measured through an external sense
resistor at CSSP and CSSN. The voltage at ISETIN also
adjusts the input current limit. Full-scale input current is
achieved when ISETIN is connected to REF, setting the
full-scale current-sense regulation voltage to 100mV.