MAX17085BETL+T Maxim Integrated Products, MAX17085BETL+T Datasheet - Page 29

• 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

Table 5. Main SMPS Fault Protection and Shutdown Operation
The selection criteria for the inductor trades off efficien-
cy, transient response, size, and cost. The MAX17085B's
charger combines all the inductor trade-offs in an opti-
mum way using the high-frequency current-mode archi-
tecture. High-frequency operation permits the use of a
smaller and cheaper inductor, and consequently results
in smaller output ripple and better transient response.
The charge current, ripple, and operating frequency
(off-time) determine the inductor characteristics. For
optimum efficiency, choose the inductance according to
the following equation:
where k = 35ns/V.
For optimum size and inductor current ripple, choose
LIR
charge current and results in a good balance between
inductor size and efficiency. Higher inductor values
decrease the ripple current. Smaller inductor values
save cost but require higher saturation current capabili-
ties and degrade efficiency.
Shutdown (ON_ = High
to Low)
Output UVP (Latched
with 4 Autorestarts)
Output OVP (Latched
with 4 Autorestarts)
Thermal Fault (Latched
with 4 Autorestarts)
V
Edge
V
Edge
V
CC
CC
CC
MAX
UVLO Falling
UVLO Rising
POR
= 0.4, which sets the ripple current to 40% of the
MODE
Charger Design Procedure
L
Integrated Charger, Dual Main Step-Down
CHG
______________________________________________________________________________________
=
4 LIR
Internal error amplifier target immediately resets to GND.
Internal error amplifier target immediately resets to GND.
After ~ 7ms timeout, the controller restarts if ON_ is still high.
Controller shuts down and the internal error amplifier target
resets to GND.
After ~ 7ms timeout, the controller restarts if ON_ is still high.
SMPS controller disabled (assuming ON_ pulled high). Internal
error amplifier target immediately resets to GND.
After the die temperature falls by ~ 50NC, the controller restarts
if ON_ is still high.
SMPS controller disabled (assuming ON_ pulled high), internal
error amplifier target immediately resets to GND.
SMPS controller enabled (assuming ON_ pulled high),
controller ramps up the output to the preset voltage.
SMPS inactive.
×
Controllers, and Dual LDO Regulators
kV
MAX
ADP
Inductor Selection
×
2
I
CHG
CONTROLLER STATE
Inductor L
least the maximum charge current plus 1/2 of the ripple
current (DIL):
The ripple current is determined by:
The output capacitor absorbs the inductor ripple cur-
rent and must tolerate the surge current delivered from
the battery when it is initially plugged into the charger.
As such, both capacitance and ESR are important
parameters in specifying the output capacitor as a filter.
Beyond the stability requirements, it is often sufficient
to make sure that the output capacitor’s ESR is much
lower than the battery’s ESR. Either tantalum or ceramic
capacitors can be used on the output. Ceramic devices
are preferable because of their good voltage ratings and
resilience to surge currents. Choose the output capacitor
based on:
CHG
must have a saturation current rating of at
I
SAT
∆
IL
Output Capacitor Selection
DL and DH immediately pulled low;
20I output discharge active.
DL and DH immediately pulled low;
20I output discharge active.
DL immediately driven high;
DH pulled low;
20I output discharge active.
DL and DH pulled low;
20I output discharge active.
DL and DH pulled low;
20I output discharge active.
DL and DH held low and 20I output
discharge active until V
the UVLO threshold.
DL and DH pulled low;
20I output discharge active.
CHG
=
I
CHG
=
4 L
+
kV
⋅
DRIVER STATE
∆
ADP
IL
CHG
2
CHG
2
CC
passes
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