MAX1613EEE-T Maxim Integrated, MAX1613EEE-T Datasheet - Page 10

• Manufacturer Part Number: MAX1613EEE-T
• Description: Battery Management
• Manufacturer: Maxim Integrated
• Series: MAX1612, MAX1613r

Bridge-Battery Backup Controllers
for Notebooks
where I
rent, V
ward drop across D1, V
average current provided by the bridge battery, and
V
channel power transistor at LX (typically 0.5V). A larger
number of cells reduces the I
reduces the discharge current, thereby extending the
discharge time. The same is true for decreasing the
output voltage or output current. For example, choose
the following values: I
V
1V for each cell, Table 2 summarizes some common
values.
Step 2: To avoid saturation, choose an inductor (L) with
a peak current rating above the I
Step 1. Use low series resistance (
mize efficiency. In this example, a 15µH inductor is
used. See Table 4 for a list of component suppliers.
The “edge-of-continuous” DC-DC algorithm causes the
inductor value to fall out of the peak current equation.
Therefore, the exact inductor value chosen is not criti-
cal to the design. However, the switching frequency is
inversely proportional to inductance, so trade-offs of
switching losses versus physical inductor size can be
made by adjusting the inductor value.
where f is the switching frequency, V
voltage, V
FET switch, V
peak current, and V
The maximum practical switching frequency is 400kHz.
Step 3: Choose the charging (C
(C
quency that the counter increments/decrements.
For instance, using a charge time of 16 hours and a dis-
charge time of one hour, C
(Consult battery manufacturers’ specifications for stan-
dard charging information, which generally compen-
sates for battery inefficiencies.)
Step 4: Using the peak current calculated in Step 1,
calculate the series resistor (R
where V
10
f
RDS(ON)
BBATT
C
CD
C
L(I
CD
______________________________________________________________________________________
CC
) timing capacitors. These capacitors set the fre-
PEAK
BBATT
1
(nF) = 4.3 · expected discharge time (in hours)
PEAK
= 2V (two cells). Using the minimum voltage of
(nF) = 4.3 · expected charge time (in hours)
BBON
RDSON
R
)
is the voltage drop across the internal N-
BBON
(V
is the bridge-battery voltage, V
D
is the peak current, I
BBATT
= 2V (internally regulated).
is the forward voltage of D1, I
is the voltage across the internal MOS-
= (V
BBATT
(V
V
OUT
BBON
RDSON
OUT
OUT
CC
is the bridge battery voltage.
= 100mA, V
is the output voltage, I
· 42,000) / I
) (V
V
= 68nF and C
BBON
RDSON
OUT
PEAK
CC
OUT
) as follows:
PEAK
≤
) and discharging
OUT
V
V )
200mΩ), to opti-
BBATT
D
is the load cur-
and, in effect,
OUT
PEAK
calculated in
is the output
CD
D
PEAK
= 5V, and
is the for-
V )
= 4.3nF.
D
is the
IN
is
Table 2. Summary of Common Values for
Designing with the MAX1612/MAX1613
Note: In this table, I
Table 3. Component List
Table 4. Component Suppliers
Step 5: Resistors R1, R2, and R3 set the DC-DC con-
verter’s output voltage and the low-battery comparator
trip value. The sum of R1, R2, and R3 must be less than
2MΩ, to minimize leakage errors. Choose resistor R1 =
750kΩ for the example. Calculate R2 and R3 as follows:
SUPPLIER
Sumida CD43
or CD54 series
AVX
Motorola
NIEC
Sanyo
Sumida
V
INDUCTORS
(V)
4.5
4.5
OUT
6
5
6
5
6
5
R2 = [ V
V
BBATT
(V)
2
2
2
3
3
3
4
4
R3 = (R1 + R2) / [ (V
USA: 207-287-5111
USA: 408-749-0510
USA: 805-867-2555
Japan: 81-3-3494-7411
USA: 619-661-6835
Japan: 81-7-2070-6306
USA: 708-956-0666
Japan: 81-3-3607-5111
OUT
I
AVERAGE
PEAK
Sprague 595D
series, AVX
TPS series
800-521-6274
CAPACITORS
(R3) - 2 (R1) - 2 (R3) ] / (2 - V
OUT
PHONE
600
500
450
400
333
300
300
250
= 100mA and battery capacity = 50mAh.
(mA)
(mA)
300
250
225
200
167
150
150
125
I
IN
TRIP
Motorola
MBR0530,
NIEC
EC10QS03L
RECTIFIERS BATTERY
USA: 207-283-1941
USA: 805-867-2556
Japan: 81-3-3494-7414
USA: 619-661-1055
Japan: 81-7-2070-1174
USA: 708-956-0702
Japan: 81-3-3607-5144
/ 1.8) - 1]
DISCHARGE TIME
(MINUTES)
MINIMUM
FAX
13.2
—
10
12
15
18
20
20
24
Sanyo
N-50AAA
OUT
)