MAX17435ETG+T Maxim Integrated Products, MAX17435ETG+T Datasheet - Page 23

• Manufacturer Part Number: MAX17435ETG+T
• Description: IC SMBUS BATT CHARGER 24TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17435ETG+T

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 8 V ~ 26 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 8. IINPVoltage() (0x3E) (continued)
The MAX17435/MAX17535 employ a synchronous step-
down DC-DC converter with an n-channel, high-side
MOSFET switch and an n-channel low-side synchronous
rectifier. The MAX17435/MAX17535 feature a pseudo-
fixed-frequency, current-mode control scheme with cycle-
by-cycle current limit. The controller’s constant off-time
(t
constant with a minimum value of 300ns. The MAX17435/
MAX17535 can also operate in discontinuous conduction
mode for improved light-load efficiency. The operation of
the DC-DC controller is determined by the following five
comparators as shown in the block diagram in Figure 2:
U The IMIN comparator sets the peak inductor current
U The CCMP comparator is used for current-mode
U The IMAX comparator provides a cycle-by-cycle
U The ZCMP comparator provides zero-crossing
U The OVP comparator checks for the battery voltage
OFF
in discontinuous mode. IMIN compares the control
signal (LVC) against 100mV (typ). When LVC voltage
is less than 100mV, DHI and DLO are both low.
regulation in continuous conduction mode. CCMP
compares LVC against the charging current feedback
signal (CSI). The comparator output is high and the
high-side MOSFET on-time is terminated when the
CSI voltage is higher than LVC.
current limit. IMAX compares CSI to 2V (corresponding
to 10A when RS2 = 10mI). The comparator output is
high and the high-side MOSFET on-time is terminated
when the current-sense signal exceeds 10A. A new
cycle cannot start until the IMAX comparator output
goes low.
detection during discontinuous conduction. ZCMP
compares the current-sense feedback signal to
500mA (RS2 = 10mI). When the inductor current
is lower than the 500mA threshold, the comparator
output is high and DLO is turned off.
) is calculated based on V
BIT
10
11
12
13
14
15
______________________________________________________________________________________
IINP Voltage, DACV 6
IINP Voltage, DACV 7
DC-DC Converter
BIT NAME
DCIN
—
—
—
—
, V
CSIN
, and a time
Low-Cost SMBus Chargers
0 = Adds 0mA of IINP voltage.
1 = Adds 828.8mV of IINP voltage.
0 = Adds 0mV of IINP voltage.
1 = Adds 1.6576V of IINP voltage to a maximum of 2.20V.
Not used. Normally a 4096mV weight.
Not used. Normally a 8192mV weight.
Not used. Normally a 16384mV weight.
Not used. Normally a 32768mV weight.
The MAX17435/MAX17535 control input current (CCS
control loop), charge current (CCI control loop), or
charge voltage (CCV control loop), depending on the
operating condition. The three control loops, CCV, CCI,
and CCS are brought together internally at the lowest
voltage clamp (LVC) amplifier. The output of the LVC
amplifier is the feedback control signal for the DC-DC
controller. The minimum voltage at the CCV, CCI, or CCS
appears at the output of the LVC amplifier and clamps
the other control loops to within 0.3V above the control
point. Clamping the other two control loops close to the
lowest control loop ensures fast transition with minimal
overshoot when switching between different control
loops (see the Compensation section).
With
MAX17535s’ inductor current never crosses zero,
which is defined as continuous conduction mode.
The MAX17435 switches at 850kHz (nominal) and the
MAX17535 switches at 500kHz (nominal) if the charger
is not in dropout (V
starts a new cycle by turning on the high-side MOSFET
and turning off the low-side MOSFET. When the charge
current feedback signal (CSI) is greater than the control
point (LVC), the CCMP comparator output goes high and
the controller initiates the off-time by turning off the high-
side MOSFET and turning on the low-side MOSFET. The
operating frequency is governed by the off-time and is
dependent upon V
At the end of the fixed off-time, the controller initiates a
new cycle if the control point (LVC) is greater than 150mV,
and the peak charge current is less than the cycle-by-
cycle current limit. Restated another way, IMIN must be
high, IMAX must be low, and OVP must be low for the
400mV above the set point and, if that condition is
detected, it disables charging.
CCV, CCI, CCS, and LVC Control Blocks
sufficient
High-Frequency,
DESCRIPTION
Continuous Conduction Mode
charge
CSIN
CSIN
and V
< 0.88 x V
current,
DCIN
.
DCIN
the
). The controller
MAX17435/
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