MAX745 Maxim, MAX745 Datasheet - Page 6

• Manufacturer Part Number: MAX745
• Description: Switch-Mode Lithium-Ion Battery-Charger
• Manufacturer: Maxim

Switch-Mode Lithium-Ion
Battery Charger
V
battery cell count.
The battery limit voltage is set by the following:
Solving for V
Set V
and determine R3 by:
Table 1. Cell-Count Programming Table
Figure 1. Standard Application Circuit
6
V
REF
BATT
0.1 F
_______________________________________________________________________________________
C4
ADJ
/ 2, the voltage limit is 4.2V. Table 1 defines the
CELL0
GND
GND
VL
VL
= cell count x V
V
ADJ
by choosing a value for R11 (typically 100k),
100k
100k
R11
1%
1%
R3 = [1 - (V
R3
ADJ
=
, we get:
9.523 V
cell count
R16
R12
ADJ
CELL1
BATT
GND
GND
REF
VL
VL
C2, 0.1µF
4.7 F
/ V
THM 1
C5
R15
10k
V
REF
IN
9.023V
)] x R11 (Figure 1)
47nF
(UP TO 24V)
10k
R2
C3
V
ADJ
CELL COUNT
REF
9.523
REF
THM/SHDN
SETI
VADJ
CCV
CCI
1
2
1
2
3
4
V
REF
VL
MAX745
GND
DCIN
IBAT
where V
(Table 1).
The voltage-regulation loop is compensated at the CCV
pin. Typically, a series-resistor-capacitor combination
can be used to form a pole-zero doublet. The pole
introduced rolls off the gain starting at low frequencies.
The zero of the doublet provides sufficient AC gain at
mid-frequencies. The output capacitor (C1) rolls off the
mid-frequency gain to below unity. This guarantees sta-
bility before encountering the zero introduced by the
C1’s equivalent series resistance (ESR). The GMV
amplifier’s output is internally clamped to between one-
fourth and three-fourths of the voltage at REF.
The charging current is set by a combination of the cur-
rent-sense resistor value and the SETI pin voltage. The
current-sense amplifier measures the voltage across
the current-sense resistor, between CS and BATT. The
current-sense amplifier’s gain is 6. The voltage on SETI
is buffered and then divided by 4. This voltage is com-
pared to the current-sense amplifier’s output.
Therefore, full-scale current is accomplished by con-
necting SETI to REF. The full-scale charging current
(I
STATUS
FS)
PGND
BATT
DLO
BST
DHI
CS
LX
is set by the following:
IN4148
REF
I
FS
D2
1/2 IRF7303
= 185mV / R1 (Figure 1)
= 4.2V and cell count is 1, 2, 3, or 4
C7
0.1 F
M1B
C6
0.1 F
1/2 IRF7303
M1A
D1
MBRS
340T3
22 H
L1
Current Control
BATTERY
D6
MBRS
340T3
0.2
R1
C1
68 F