MAX1538ETI+T Maxim Integrated Products, MAX1538ETI+T Datasheet - Page 20

• Manufacturer Part Number: MAX1538ETI+T
• Description: IC PWR SOURCE SELECTOR 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1538ETI+T

• Function: Dual Battery Controller
• Battery Type: All Battery Types
• Voltage - Supply: 4.75 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Power-Source Selector for
Dual-Battery Systems
where V
I
the battery’s inductance. C
adequate for typical applications. Adding capacitance
at BAT_ pins lengthens the time needed to detect bat-
tery removal. See the Battery-Absence-Detection Delay
section.
Upon adapter removal the adapter’s connector may
bounce. To avoid false detection of adapter reinsertion
select R1, R2, and R3 according to the following equation:
where V
ing an AC adapter and airline-adapter voltage when
removing an airline adapter, C
at ADPIN, and t
the Airline Mode and AC Adapter section for a defini-
tion of V
When a selected battery is removed, the system load
quickly pulls BAT_ below 5 x V
source is selected. The battery is considered present
and undervoltage until V
another power source is quickly switched to the system
load, capacitance at BAT_ (see the Inductive "Kick"
section) delays the detection of the removed battery. If
another battery is inserted before this delay has
passed, it is considered undervoltage. Calculate the
delay using the following equation:
where I
a 5MΩ internal resistor), and C
from BAT_ to GND. When C
corresponds to a 5s time constant. If this time is unac-
ceptable, use a smaller capacitance or connect a resis-
tor or current sink from BAT_ to GND.
20
CHG_MAX
R
1
+
______________________________________________________________________________________
R
BAT_
_Threshold
Adapter
2
BAT__MIN
is the maximum charge current, and L
+
Battery-Absence-Detection Delay
t
is the 3.9µA BAT_ quiescent current (due to
R
Absence delay
3
is the AC-adapter voltage when remov-
<
Bounce
Adapter Removal Debouncing
.
C
ADPIN
is the minimum battery voltage,
_
is the 5ms debounce time. See
V
BAT_
_
×
Threshold
=
BAT_
(
BAT_
V
19
ADPIN
Adapter
falls below 2V. Although
BAT_
V
values of 0.01µF are
I
= 1µF, t
×
BAT
MINV_
×
is the capacitance
is the capacitance
C
t
−
BAT
Bounce
V
and another
Absence_delay
_
_
Threshold
BAT_
)
is
The MAX1538 selector fits in a very small layout.
Ensure that C1 is placed close to V
Connect the paddle to GND directly under the IC. A
complete layout example is shown in Figure 10.
Because BATA and BATB are high-impedance nodes,
prevent leakage current between BATA/BATB and
other high-voltage sources by carefully routing traces.
Note that flux remaining on the board can significantly
contribute to leakage current. See the Leakage Current
into BAT_ section.
Minimize parasitic inductance in the BATA and BATB
path to reduce inductive kick during battery discon-
nect. This reduces the capacitance requirement at
BATA and BATB.
TRANSISTOR COUNT: 5431
PROCESS: BiCMOS
*EXPOSED PADDLE
BATSEL
MINVA
MINVB
RELRN
CHRG
OUT0
OUT1
1
2
3
4
5
6
7
(5mm x 5mm)
MAX1538 *
THIN QFN
Pin Configuration
Chip Information
21
20
19
18
17
16
15
DD
N.C.
CHGB
CHGA
DISBAT
CHGIN
EXTLD
N.C.
and GND.
Layout