MAX8900BEWV+T Maxim Integrated Products, MAX8900BEWV+T Datasheet - Page 30

• Manufacturer Part Number: MAX8900BEWV+T
• Description: IC LI-ION/POLY BATT CHRGR 30WLP
• Manufacturer: Maxim Integrated Products

Specifications of MAX8900BEWV+T

• Function: Battery Monitor
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 3.4 V ~ 8.7 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 30-WLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1.2A Switch-Mode Li+ Chargers with ±22V Input
Rating and JEITA Battery Temperature Monitoring
capacitor (C
greater. If C
than 1:10 between C
to drive the high-side n-channel gate. The minimum AVL
capacitor is 0.1FF with a voltage rating of 6.3V. The mini-
mum PVL capacitor is 1.0FF with a voltage rating of 6.3V.
Ceramic capacitors with X5R or X7R dielectric are highly
recommended due to their small size, low ESR, and small
temperature coefficients.
Certain applications require dynamic programming of the
charge current. For example, if the input supply is a USB
source, then the system might need to adjust the charge
current to support the 100mA and 500mA input current
ratings dictated by the USB-IF. Figure 2 illustrates one
approach to dynamically program the charge current. By
driving the gates of two MOSFET switches to logic-high
or logic-low, a microprocessor (FP) connects or discon-
nects different program resistors. This method allows for
four different charge current values ranging from 95mA
to 1187mA. When a MOSFET is turned on, its associated
resistor is connected to SETI. As resistors are added
in parallel, the total resistance from SETI to ground
decreases, which causes I
In the particular example of a USB input, the circuit of
Figure 2 could be leveraged as follows: When a VBUS
connect event is detected, the FP can immediately initi-
ate the USB 100mA current mode by setting GPIO[6:4]
= 0b000. After the USB transceiver has enumerated with
500mA permission, the FP can initiate the USB 500mA
current mode by setting GPIO[6:4] = 0b010. If the USB
transceiver detects that a USB suspend is needed, then
the FP can reduce the input current to 40FA by set-
ting GPIO[6:4] = 0b001. Alternatively, it is possible that
after the VBUS connect event that the USB transceiver
determines that there is a dedicated USB wall charger
(D+ and D- shorted together) and then the FP can set
the charge current to the full capability of the MAX8900_
(1.2A) by setting GPIO[6:4] = 0b110.
No-battery operation may be necessary in the applica-
tion and/or end-of-line testing during production. The
MAX8900_ can operate a system without a battery as
long as the following conditions are satisfied:
U The system must not draw load currents that are
30
greater than I
Dynamic Charge Current Programming
BST
BST
) is a 0.1FF with a voltage rating of 10V or
is increased then maintain a ratio of less
Applications Information
FC
.
BST
and C
FC
No-Battery Operation
to increase.
PVL
. C
BST
stores charge
U The system must not draw load currents that are
U The thermistor node (THM) must be satisfied. Note
U The battery node should have enough capacitance
A battery charger’s input is typically very accessible to
the end-user (i.e., available on a connector) and can
potentially be exposed to very harsh conditions. The
MAX8900_ provides for high-reliability solution that can
survive harsh conditions seen on its input.
Charge source impedance can vary due to quality of
the charge source and the associated connectors. The
MAX8900_ operates very nicely with input impedance
up to 1I. When high input impedances cause the input
voltage to drop, the MAX8900_ simply reduces the
charge current to a sustainable level and tries to put as
much energy into the battery as possible. If the input
voltage falls within the V
voltage, the MAX8900_ shuts down to prevent any cur-
rent flowing from the battery back to the charger source.
The MAX8900_ does not suffer from the self-oscillation
problems that plague other chargers when exposed to
high-impedance sources.
Often the input source has long leads connecting to the
MAX8900_, which, during connection and disconnect,
can cause voltage spikes. The lead inductance and the
input capacitor create an LC tank circuit. In the event
that the LC tank circuit has a high Q (i.e., low series
greater than I
that if the thermistor is in the battery pack and the
pack is removed, the MAX8900_ THM node voltage
goes high and disables the charger. If the MAX8900_
is expected to deliver charge without a battery then
V
to hold the battery voltage to some minimum accept-
able system value (V
charge state transition time of 100Fs (t
For example, if the maximum system load without a
battery could be 300mA (I
acceptable system voltage is 3.4V (V
the battery node should have at least 37.5FF.
THM
must be forced to AVL/2.
C
C
BAT
BAT
PQ
≥
≥
I
300mA
LOAD
when the battery is less than V
SYSRST
×
IN2BAT
×
V
4.2V - 3.4V
BATREG
Charge-Source Impedance
Charge-Source Issues
100 s
t
LOAD
) during the done-to-fast-
DONE2FC
threshold of the battery
F
- V
) and the minimum
=
SYSRST
35.7 F
Inductive Kick
DONE2FC
SYSRST
F
PQUTH
), then
).
.