MP2610 MPS, MP2610 Datasheet - Page 13

• Manufacturer Part Number: MP2610
• Description: 2a, 24v Input, 1.1mhz 1/2 - Cell Switching Li-ion Battery Charger
• Manufacturer: MPS

APPLICATION INFORMATION
Setting the Charge Current
The charge current of MP2610 is set by the
sense resistor RS1 (Figure1). The charge current
programmable formula is as following:
Selecting the Inductor
A 1µH to 10µH inductor is recommended for
most applications. The inductance value can be
derived from the following equation.
is 1/2 Cell battery voltage.
Choose inductor current to be approximately
30% if the maximum charge current, 2A. The
maximum inductor peak current is:
Under light load conditions below 100mA, larger
inductance
efficiency.
For
resistance is recommended to be less than
200mΩ.
NTC Function
As Figure 6 shows, the low temperature
threshold and high temperature threshold are
preset internally via a resistive divider, which are
73%·VREF33 and 30%·VREF33. For a given
NTC thermistor, we can select appropriate R3
and R6 to set the NTC window.
In detail, for the thermistor (NCP18XH103) noted
in above electrical characteristic,
At 0ºC, R
At 50ºC, R
MP2610 Rev. 0.91
7/13/2010
Where ΔI
optimized
NTC_Cold
NTC_Hot
L
L
is the inductor ripple current. VOUT
is
MP2610 – 2A, 24V INPUT, 1.1MHz 1-2CELL SWITCHING LI-ION BATTERY CHARGER
I
Table2—I
=
I
CHG
I
L(MAX)
1.5
0.8
0.5
CHG
2
1
V
= 27.445kΩ;
= 4.1601kΩ.
OUT
recommended
efficiency,
(A)
(A)
V
IN
=
×
=
× Δ ×
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
I
LOAD
(V
RS1(m
CHG
200mV
I
IN
L
−
+
Setting
f
RS(mΩ)
V
OSC
Δ
the
Ω
OUT
2
100
133
200
250
400
I
L
)
)
for
inductor
© 2010 MPS. All Rights Reserved.
improved
www.MonolithicPower.com
DC
(1)
(2)
(3)
Assume that the NTC window is between 0ºC
and 50ºC, the following equations could be
derived:
According to equation (4) and equation (5), we
can find that R3 = 9.63k and R6 = 505k.
To be simple in project, making R3=10k and R6
no
specification.
Selecting the Input Capacitor
The input capacitor reduces the surge current
drawn from the input and also the switching noise
from the device. The input capacitor impedance
at the switching frequency should be less than
the input source impedance to prevent high
frequency switching current passing to the input.
Ceramic capacitors with X5R or X7R dielectrics
are highly recommended because of their low
ESR and small temperature coefficients. For
most applications, a 4.7µF capacitor is sufficient.
Selecting the Output Capacitor
The output capacitor keeps output voltage ripple
small and ensures regulation loop stability. The
output capacitor impedance should be low at the
switching frequency. Ceramic capacitors with
X5R or X7R dielectrics are recommended.
R6
connect
R3
R3
R6//R
R6//R
Figure 6— NTC function block
+
+
R6//R
R
R6//R
R3
NTC
VREF33
NTC_Cold
NTC_Hot
will
NTC_Cold
NTC
NTC_Hot
approximately
=
=
VREF33
VREF33
V
Low Temp Threshold
V
High Temp Threshold
TH_High
TH_Low
V
V
=
TH_Low
TH_High
=
30%
73%
meet
the
(4)
(5)
13