MAX17085BETL+T Maxim Integrated Products, MAX17085BETL+T Datasheet - Page 22

• Manufacturer Part Number: MAX17085BETL+T
• Description: Battery Management Dual Main Step-Down Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX17085BETL+T

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

Integrated Charger, Dual Main Step-Down
Controllers, and Dual LDO Regulators
The MAX17085B charger has three regulations loops: a
voltage-regulation loop (CCV) and two current-regulation
loops (CCI and CCS). The loops operate independently
of each other. The CCV voltage-regulation loop monitors
BATT to ensure that its voltage never exceeds the volt-
age set by VCTL and CELLS. The CCI battery charge
current-regulation loop monitors current delivered to
BATT to ensure that it never exceeds the current limit
set by ISET. The charge current-regulation loop is in
control as long as the battery voltage is below the set
point. When the battery voltage reaches its set point,
the voltage-regulation loop takes control and maintains
the battery voltage at the set point. A third loop (CCS)
takes control and reduces the charge current when
the adapter current exceeds the input current limit. The
CCI current loop is internally compensated while the
CCS and CCV loops are externally compensated with a
capacitor at the CC pin.
The new thermally optimized high-frequency architecture
controls the power dissipation in the high-side MOSFET,
resulting in reduced output capacitance and inductance.
The MAX17085B features separate control inputs to set
the per-cell voltage and the number of cells in series.
The VCTL input sets the per-cell voltage, while the
CELLS input sets the total number of cells in series.
Together, these two inputs set the charge voltage at the
BATT input, providing a flexible way to support different
cell types and different battery-pack configurations.
The MAX17085B supports charge voltages of 4.0V/cell
to 4.4V/cell based on the following equation:
The dynamic range of the VCTL input is limited, so it
is possible to achieve ±0.5% charge voltage accuracy
using resistive voltage-dividers composed of 1% accu-
rate resistors.
Figure 3 shows a simple method to set two different
CELL voltages using a logic output from the embedded
controller.
Connecting VCTL to REF = 2.10V, which gives
4.375V/cell.
The trilevel CELLS input allows simple switching between
2, 3, and 4 cells in series.
22
_____________________________________________________________________________________
Charger Detailed Description
Setting the Per-Cell Charge Voltage (VCTL)
V
BATT
Setting the Number of Cells (CELLS)
Setting the Charge Voltage
Cell 2.083 VCTL
=
×
The ISET input controls the voltage across current-sense
resistor RS2. ISET can accept either analog or digital
inputs. The full-scale differential voltage between CSIP
and CSIN is 100mV (5A for RS2 = 20mI).
Important: Keep ISET low during the initial power-up of
the MAX17085B. Wait 10ms to allow PDSL to reach its
final voltage before enabling the battery charger.
When the MAX17085B powers up and the charger is
ready, if there are no two clock edges within 20ms, the
circuit assumes ISET is an analog input, and disables the
PWM filter block. For ISET analog input, set ISET accord-
ing to the following equation:
The input range for ISET is from 0 to REF. To shut down
the charger, pull ISET below 26mV.
Table 3. CELLS Pin Setting
Figure 3. VCTL Setting
CELLS PIN
VOLTAGE
> 2.8V
OPEN
GND
V
CONTROL
CELL
V
CELL
VCTL
(L) = 2.083 O
(H) = 2.083 O
COUNT
CELLS
I
R3
CHG
Setting Charge Current (ISET)
2
3
4
V
R1 + R2//R3
REF
V
R1 + R2
=
REF
R1
O R2//R3
100mV
O R2
RS2
Charge with 2 times the cell
voltage programmed at VCTL
Charge with 3 times the cell
voltage programmed at VCTL
Charge with 4 times the cell
voltage programmed at VCTL
R2
×
REF
VCTL
V
V
ISET
REF
MAX17085B
SETTING
Analog ISET