DC1645A-D Linear Technology, DC1645A-D Datasheet - Page 12

• Manufacturer Part Number: DC1645A-D
• Description: BOARD EVAL LTM8061-8.4
• Manufacturer: Linear Technology
• Series: LTM®, uModule®r

Specifications of DC1645A-D

• Main Purpose: Power Management, Battery Charger
• Embedded: No
• Utilized Ic / Part: LTM8061
• Primary Attributes: 2 Cell- Li-Ion, 8.2V 2A Output
• Secondary Attributes: LED Status Indicators
• Lead Free Status / RoHS Status: Not applicable / Not applicable

APPLICATIONS INFORMATION
LTM8061
V
The LTM8061 is biased directly from the charger input
supply through the V
currents, so a high quality, low ESR decoupling capacitor
is recommended to minimize voltage glitches on V
4.7μF capacitor is typically adequate for most charger
applications.
Reverse Protection Diode
The LTM8061 integrates a high voltage power Schottky
diode to provide input reverse voltage protection. The
anode of this diode is connected to V
is connected to V
at each end; please see the Block Diagram.
BIAS Pin Considerations
The BIAS pin is used to provide drive power for the internal
power switching stage and operate other internal circuitry.
For proper operation, it must be powered by at least 2.9V
and no more than the absolute maximum rating of 10V. In
most applications, connect BIAS to BAT.
When charging a 2-cell battery using a relatively high input
voltage, the LTM8061 power dissipation can be reduced
by connecting BIAS to a 3.3V source.
BAT Decoupling Capacitance
In many applications, the internal BAT capacitance of the
LTM8061 is suffi cient for proper operation. There are cases,
however, where it may be necessary to add capacitance or
otherwise modify the output impedance of the LTM8061.
Case 1: the μModule charger is physically located far from
the battery and the added line impedance may interfere with
the control loop. Case 2: the battery ESR is very small or
very large; the LTM8061 controller is designed for a wide
range, but some battery packs have an ESR outside of this
range. Case 3: there is no battery at all. As the charger is
designed to work with the ESR of the battery, the output
may oscillate if no battery is present.
12
IN
Input Supply
IN
. There is a small amount of capacitance
IN
pin. This pin carries large switched
INA
, and the cathode
IN
. A
The optimum ESR is about 100mΩ, but ESR values both
higher and lower will work. Table 1 shows a sample of
parts verifi ed by Linear Technology:
Table 1. Recommended BAT Capacitors
PART NUMBER
16TQC22M
35SVPD18M
TPSD226M025R0100
T495D226K025AS
TPSC686M006R0150
TPSB476M006R0250
APXE100ARA680ME61G
APS-150ELL680MHB5S
If system constraints preclude the use of electrolytic ca-
pacitors, a series R-C network may be used. Use a ceramic
capacitor of at least 22μF and an equivalent resistance of
100mΩ.
CLP: Input Current Limit
The LTM8061 contains a PowerPath™ control feature to
support multiple load systems. The charger adjusts charge
current in response to a system load if input supply current
exceeds the programmed maximum value. Maximum input
supply current is set by connecting a sense resistor (R
as shown in Figure 3. The LTM8061 begins to limit the
charge current when the voltage across the sense resistor
is 50mV. The maximum input current is defined by:
R
CLP
INPUT SUPPLY
Figure 3. R
= 0.05/(Max Input Current)
CLP
Sets the Input Supply Current Limit
R
CLP
DESCRIPTION
22μF , 16V, POSCAP
18μF , 35V, OS-CON
22μF , 25V Tantalum
22μF , 25V, Tantalum
68μF , 6V, Tantalum
47μF , 6V, Tantalum
68μF , 10V Aluminum
68μF , 25V Aluminum
SYSTEM LOAD
V
V
IN
INC
/CLP
LTM8061
MANUFACTURER
Sanyo
Sanyo
AVX
Kemet
AVX
AVX
Nippon Chemicon
Nippon Chemicon
8061 F03
CLP
8061f
)