MAX8903JETI+ Maxim Integrated, MAX8903JETI+ Datasheet - Page 22

• Manufacturer Part Number: MAX8903JETI+
• Description: Battery Management 2A 1-Cell Li+ DC-DC USB/Adapter Charger
• Manufacturer: Maxim Integrated
• Series: MAX8903A, MAX8903B, MAX8903C, MAX8903D, MAX8903E, MAX8903G, MAX8903H, MAX8903J, MAX8903Yr

Specifications of MAX8903JETI+

• Rohs: yes
• Battery Type: Li-Ion
• Output Voltage: 5 V
• Output Current: 1 mA
• Operating Supply Voltage: 4.1 V to 16 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Charge Safety Timers: Yes
• Maximum Power Dissipation: 1666.7 mW
• Operating Supply Current: 2.3 mA
• Product Type: Charge Management
• Temperature Monitoring: Yes
• Uvlo Start Threshold: 3.2 V

where:
R
ture T in Celsius
R
β = The material constant of the thermistor, which typi-
cally ranges from 3000K to 5000K
T = The temperature of the thermistor in °C
Table 3 shows the MAX8903_ THM temperature limits
for different thermistor material constants.
Some designs might prefer other thermistor temperature
limits. Threshold adjustment can be accommodated by
changing R
parallel with the thermistor, or using a thermistor with dif-
ferent β. For example, a +45°C hot threshold and 0°C
cold threshold can be realized by using a thermistor
with a β of 4250 and connecting 120kΩ in parallel. Since
the thermistor resistance near 0°C is much higher than it
is near +50°C, a large parallel resistance lowers the
cold threshold, while only slightly lowering the hot
threshold. Conversely, a small series resistance raises
the hot threshold, while only slightly raising the cold
threshold. Raising R
thresholds, while lowering R
Note that since VL is active whenever valid input power
is connected at DC or USB, thermistor bias current
flows at all times, even when charging is disabled (CEN
= high). When using a 10kΩ thermistor and a 10kΩ
pullup to VL, this results in an additional 250µA load.
This load can be reduced to 25µA by instead using a
100kΩ thermistor and 100kΩ pullup resistor.
The power enabled on battery detection function allows
the MAX8903B/MAX8903E/MAX8903G to automatically
enable/disable the USB and DC power inputs when the
battery is applied/removed. This function utilizes the
battery pack’s integrated thermistor as a sensing mech-
anism to determine when the battery is applied or
removed. With this function, MAX8903B/MAX8903E/
MAX8903G-based systems shut down when the battery
is removed regardless of whether external power is
available at the USB or DC power inputs.
The MAX8903B/MAX8903E/MAX8903G implement the
power enabled on battery detection function with the ther-
mistor detector comparator as shown in Figure 7. If no bat-
tery is present, the absence of the thermistor allows R
pull THM to VL. When the voltage at the THM pin increases
above 87% of VL, it is assumed that the battery has been
removed and the system powers down. However, there is
also the option to bypass this thermistor sensing option
completely, and so retain the ability to remove the battery
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MAX8903A–E/G/H/J/N/Y
22
T
25
= The resistance in Ω of the thermistor at tempera-
= The resistance in Ω of the thermistor at +25°C
TB
, connecting a resistor in series and/or in
Power Enable on Battery Detection
TB
lowers both the cold and hot
TB
raises both thresholds.
TB
to
and let the system continue to operate with external power.
If the THM pin is tied to GND (voltage at THM is below 3%
of VL), the thermistor option is disabled and the system
does not respond to the thermistor input. In those cases, it
is assumed that the system has its own temperature sens-
ing, and halts changing through CEN when the tempera-
ture is outside of the safe charging range.
Based on the version of the MAX8903_, the SYS load
regulation is either 25mV/A or 40mV/A. The 25mV/A ver-
sions achieve better load regulation by increasing the
feedback loop gain. To ensure feedback stability with
this higher gain, a larger SYS output capacitor is
required. Devices with 25m/V SYS load regulation
require 22µF SYS output capacitor whereas devices
with 40m/V only require 10µF. See Table 6 for more
information about the various versions of the
MAX8903_.
The MAX8903_'s control scheme requires an external
inductor (L
This section describes the control scheme and the consid-
erations for inductor selection. Table 5 shows recommend-
ed inductors for typical applications. For assistance with
the calculations needed to select the optimum inductor for
a given application, refer to the spreadsheet at:
www.maximintegrated.com/design/tools/calcula-
tors/files/MAX8903-INDUCTOR-DESIGN.xls.
The MAX8903 step-down DC-DC regulator implements a
control scheme that typically results in a constant switch-
ing frequency (f
a value near the output voltage, high duty cycle operation
occurs and the device can operate at less than f
to minimum off-time (t
cycle operation, the regulator operates with t
a peak current regulation. Similarly, when the input
voltage is too high to allow f
Table 4. Package Thermal Characteristics
Continuous
Power
Dissipation
θ
θ
JA
JC
OUT
28-PIN 4mm x 4mm THIN QFN
SINGLE-LAYER PCB
1666.7mW
Derate 20.8mW/°C
above +70°C
48°C/W
3°C/W
) from 1.0µH to 10µH for proper operation.
Minimum SYS Output Capacitor
SW
). When the input voltage decreases to
Step-Down DC-DC Regulator
OFFMIN
SW
Inductor Selection for
) constraints. In high duty
operation due to minimum
Power Dissipation
MULTILAYER PCB
2286mW
Derate 28.6mW/°C
above +70°C
35°C/W
3°C/W
Maxim Integrated
OFFMIN
SW
due
and