MAX1870AETJ+ Maxim Integrated Products, MAX1870AETJ+ Datasheet - Page 22

• Manufacturer Part Number: MAX1870AETJ+
• Description: Battery Management Li+ Step Up/Step Down Battery Charger
• Manufacturer: Maxim Integrated Products

Specifications of MAX1870AETJ+

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Step-Up/Step-Down
Li+ Battery Charger
•
•
Figure 8. MAX1870A Step-Up/Step-Down Inductor-Current Waveform
22
A)
B)
CCMP: CCMP compares the current-mode control
point, LVC, to the inductor current. In step-down
mode, the off-time (state A) is terminated when the
inductor current falls below the current threshold
set by LVC. In step-up mode, the on-time (state C)
is terminated when the inductor current rises above
the current threshold set by LVC.
IMAX: The IMAX comparators provide a cycle-by-
cycle inductor current limit. This circuit compares
the inductor current (CSI in step-down mode or
CSS in step-up mode) to the internally fixed cycle-
______________________________________________________________________________________
MINIMUM
STEP-UP
ON-TIME
STATE C
STATE C
PEAK REGULATED
PRECALCULATED STEP-UP
STEP-UP
ON-TIME
STATE B
STATE B
OFF-TIME
VALLEY REGULATED
STEP-DOWN
OFF-TIME
STATE A
STATE A
STATE B
STATE B
PRECALCULATED STEP-DOWN
PRECALCULATED STEP-DOWN
STEP-DOWN
MINIMUM
OFF-TIME
ON-TIME
ON-TIME
dl
dt
•
=
V
BATT
by-cycle current limit. The current-sense voltage
limit is 200mV. With RS1_ = RS2 = 30mΩ, which
corresponds to 6.7A. If the inductor current-sense
voltage is greater than V
on-time is terminated or a step-down on-time is not
permitted.
ZCMP: The ZCMP comparator detects when the
inductor current crosses zero. If the ZCMP output
goes high during a step-down off-time, the
MAX1870A switches to the idle state (state D) to
conserve power.
L
- V
IN
dl
dt
=
V
L
IN
IMAX
(200mV), a step-up
dl
dt
=
V
BATT
L