MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = float, CLS =
REF, V
BST
- V
LX
= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
REF Undervoltage-Lockout Trip
Point
V
REF
falling 3.1 3.9 V
TRIP POINTS
BATT Power-Fail Threshold V
DCIN
falling, referred to V
CSIN
50
100
150 mV
BATT Power-Fail Threshold
Hysteresis
200
mV
ACIN Threshold ACIN rising
2.007 2.048 2.089
V
ACIN Threshold Hysteresis 0.5% of REF 20 mV
ACIN Input Bias Current V
ACIN
= 2.048V -1 +1 µA
SWITCHING REGULATOR
DHI Off-Time
V
BATT
= 16V, V
DCIN
= 19V,
V
CELLS
= V
REFIN
0.36
0.44
µs
DHI Minimum Off-Time
V
BATT
= 16V, V
DCIN
= 17V,
V
CELLS
= V
REFIN
0.24 0.28 0.33
µs
DHI Maximum On-Time 2.5 5 7.5 ms
DLOV Supply Current I
DLOV
DLO low 5 10 µA
BST Supply Current I
BST
DHI high 6 15 µA
BST Input Quiescent Current
V
DCIN
= 0, V
BST
= 24.5V,
V
BATT
= V
LX
= 20V
0.3 1 µA
LX Input Bias Current V
DCIN
= 28V, V
BATT
= V
LX
= 20V
150
500 µA
LX Input Quiescent Current V
DCIN
= 0, V
BATT
= V
LX
= 20V 0.3 1 µA
DHI Maximum Duty Cycle 99
99.9
%
Minimum Discontinuous-Mode
Ripple Current
0.5 A
Battery Undervoltage Charge
Current
V
BATT
= 3V per cell (RS2 = 15mΩ),
MAX1908 only, V
BATT
rising
150 300
450 mA
CELLS = GND, MAX1908 only, V
BATT
rising 6.1 6.2 6.3
CELLS = float, MAX1908 only, V
BATT
rising
9.15
9.45
Battery Undervoltage Current
Threshold
CELLS = V
REFIN
, MAX1908 only, V
BATT
rising 12.2 12.4 12.6
V
DHI On-Resistance High V
BST
- V
LX
= 4.5V, I
DHI
= +100mA 4 7 Ω
DHI On-Resistance Low V
BST
- V
LX
= 4.5V, I
DHI
= -100mA 1 3.5 Ω
DLO On-Resistance High V
DLOV
= 4.5V, I
DLO
= +100mA 4 7 Ω
DLO On-Resistance Low V
DLOV
= 4.5V, I
DLO
= -100mA 1 3.5 Ω
ERROR AMPLIFIERS
GMV Amplifier Transconductance
GMV
V
V C T L
= V
LD O
, V
BAT T
= 16.8V ,
C E LLS = V
RE F IN
0.0625 0.125 0.2500
GMI Amplifier Transconductance
GMI V
ICTL
= V
RE F IN
, V
CSIP
- V
CSIN
= 75mV 0.5 1 2.0
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