MAX8677AETG+T Maxim Integrated Products, MAX8677AETG+T Datasheet - Page 13
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MAX8677AETG+T
Manufacturer Part Number
MAX8677AETG+T
Description
IC USB/AC ADP CHARGER 24-TQFN
Manufacturer
Maxim Integrated Products
Datasheet
1.MAX8677AETG.pdf
(21 pages)
Specifications of MAX8677AETG+T
Function
Charge Management
Battery Type
Lithium-Ion (Li-Ion)
Voltage - Supply
4.1 V ~ 6.6 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 1. External Components List for Figures 2 and 3
The MAX8677A features OVP. Part of this protection is
a 5.3V voltage limiter at SYS. If the DC or USB input
exceeds 5.3V, SYS still limits at 5.3V. It is expected that
the SYS limiter will not need to operate, and will be in
dropout in most cases. A typical 5VAC adapter oper-
ates below the limit level, so both DC and SYS would
be at 5V in that case.
The MAX8677A has numerous other charging and
power-management features, which are detailed in the
following sections.
The MAX8677A Smart Power Selector seamlessly dis-
tributes power between the external inputs, the battery,
and the system load (Figure 4). The basic functions
performed are:
•
Figure 4. Smart Power Selector Block Diagram
ADAPTER
(FIGURES 2, 3)
COMPONENT
USB
With both an external power supply (USB or
adapter) and battery connected:
R
AC
PU
R
R
C
C
THM
C
PSET
CL
CT
RT
ISET
SYS
BAT
IN
(x 4)
USB
DC
Q1
Q2
1.5A Dual-Input USB/AC Adapter Charger
Input filter capacitor
VL filter capacitor
SYS output bypass capacitors
Battery bypass capacitor
Charger timing capacitor
Logic output pullup resistors
Negative TC thermistor
THM pullup resistor
Input current-limit programming resistor
Fast-charge current programming resistor
______________________________________________________________________________________
MAX8677A
CHARGE AND
CURRENT
CHARGE
SYS LOAD
SWITCH
Smart Power Selector
Q3
FUNCTION
LOAD
CURRENT
SYS
BAT
GND
SYSTEM
LOAD
BATTER
and Smart Power Selector
4.7µF ceramic capacitor
0.1µF ceramic capacitor
10µF ceramic capacitor
4.7µF ceramic capacitor
0.068µF low TC ceramic capacitor
560kΩ
Phillips NTC thermistor, P/N 2322-640-63103, 10kΩ ±5% at +25°C
10kΩ ±1%
1.5kΩ ±1% for 2A limit
3kΩ ±1% for 1A charging
•
•
A thermal-limiting circuit reduces the battery charge
rate and external power-source current to prevent the
MAX8677A from overheating.
An internal 40mΩ MOSFET connects SYS to BAT (Q3,
Figure 4) when no voltage source is available at DC or
USB. When an external source is detected at DC or
USB, this switch is opened and SYS is powered from
the valid input source through the input limiter.
The SYS-BAT switch also holds up SYS when the sys-
tem load exceeds the input current limit. If that should
happen, the SYS-BAT switch turns on so that the bat-
tery supplies additional SYS load current. If the system
load continuously exceeds the input current limit, the
battery does not charge, even though external power is
connected. This is not expected to occur in most
cases, since high loads usually occur only in short
peaks. During these peaks, battery energy is used, but
at all other times the battery charges.
When the battery is connected and there is no
external power input, the system is powered from
the battery.
When an external power input is connected and
there is no battery, the system is powered from the
external power input.
When the system load requirements are less
than the input current limit, the battery is
charged with residual power from the input.
When the system load requirements exceed the
input current limit, the battery supplies supple-
mental current to the load.
PART
System Load Switch
13