- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄375262 > ADP3801AR (ANALOG DEVICES INC) Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.50V) 8-SM8 -40 to 110 PDF資料下載
參數(shù)資料
| 型號： | ADP3801AR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 電源管理 |
| 英文描述： | Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.50V) 8-SM8 -40 to 110 |
| 中文描述： | 2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| 封裝： | SOIC-16 |
| 文件頁數(shù)： | 13/20頁 |
| 文件大?。?/td> | 256K |
| 代理商： | ADP3801AR |
ADP3801/ADP3802
–13–
REV. 0
Current Sense
The maximum charging current is specified by the battery
manufacturer as 4.0 A. To avoid losing excessive power on the
current-sense resistor, it is advisable to keep the voltage drop
across the resistor at maximum current to 160 mV or below.
Thus, R
CS
= 0.16 V/4 A = 40 m
. The resistor’s maximum
power rating can be calculated using the data sheet specification
for the Overcurrent Comparator. The overcurrent protection is
specified at 4.9 A when using a 40 m
resistor; therefore, the
resistor has to be rated at P
R
= (4.9)
2
×
0.04 = 0.96 W. Thus a
1.0 W or higher power rated resistor should be used. Two
2.2 nF capacitors are connected from the CS+ and CS– inputs
to ground to filter out high frequency switching noise.
ISET Programming Voltage
This voltage programs the charge current based on the above
calculated R
CS
. Using the data sheet specification for the current
programming at the ISET input of 0.1 V/V, we need:
V
R
I
V V
/
A
V V
/
V
ISET
CS
CHARGE
=
×
.
=
×
=
0 1
0 04
.
4 0
.
0 1
.
1 6
.
The 1.6 V can be obtained from the 3.3 V LDO by a resistor
divider of 20 k
and 22 k
.
PROG Voltage
Next, the PROG voltage has to be determined to set the proper
final battery voltage. From the data sheet, V
PROG
for two Li-Ion
batteries in series (12.6 V) is between 2.05 V and 2.3 V. A 2.2 V
input can be obtained from the 3.3 V LDO by a resistor divider
of 66.5 k
and 33.2 k
.
ADJ Voltage
Since no further adjustment of the final battery voltage is re-
quired, this pin is tied to the VL pin, which disables the internal
amplifier.
Output Voltage and Duty Cycle
A Buck type of converter’s output voltage V
O
can be calculated
as follows:
V
V
D
V
T
×
T
O
IN
100
IN
100
ON
=
×
=
×
In the above equation,
D
is the maximum duty cycle of the
converter in percentage, and
T
ON
and
T
are the ON time and
total period respectively. Setting V
INMIN
= 15 V provides margin
for external voltage drops and the common-mode input range of
the current sense amplifier.
For
V
IN
= 11
V
:
D
MAX
=
V
O
×
100 /
V
IN
= 12.6
×
100 / 15 = 84%
For
V
IN
= 20
V
:
D
MAX
=
V
O
×
100 /
V
IN
= 12.6
×
100 / 20 = 63%
Buck Inductor
The inductor value can be calculated after determining the
allowable amount of inductor ripple current. For continuous
buck operation, and considering low cost inductor core materi-
als and acceptable core losses at 200 kHz, the usual peak-to-
peak inductor ripple current (I
RPP
) used is 20%-40% of the
maximum dc current. Using 25% of 4.0 A
DC
gives I
RPP
= 1.0 A
PP
.
The maximum off-time of the Buck switch (T
OFFMAX
) occurs at
the maximum input voltage of 20 V:
T
D
×
f
kHz
s
OFFMAX
MAX
100
OSC
=
=
×
=
100
100
63
200
100
1 9
μ
This gives an inductor value of:
L
V
T
I
V
s
A
H
OMAX
OFFMAX
RPP
>
×
=
×
=
12 6
1 9
.
1 0
.
24
.
μ
μ
The max inductor peak current is calculated as follows:
I
LPEAK
=
I
DC
+
I
RPP
/2 = 4.0 + 1.0/2 = 4.5
A
PEAK
The max inductor rms current is calculated (where 0.577 is the
conversion factor for a peak to RMS value):
An appropriate inductor is the Coiltronix UP4B330, which is
specified at 33
μ
H and can carry the 4.5 A current with about a
20
°
C temperature rise. For the ADP3802, the above formulas
give:
T
OFFMAX
= 0.74
μ
s
and
L
= 10
μ
H
.
PFET Selection and Thermal Design
We have to consult the available P-channel MOSFET (PFET)
transistor selection charts for switch-mode power supply appli-
cations to find a PFET in the desired package whose Safe
Operation Area (SOA) would meet the maximum V
IN
and I
O
requirements with acceptable margin. For this application, the
Temic Si4463 was selected in an SO-8 package. This transistor
is specified at V
DSS
= –20 V, V
GSMAX
= 12 V, R
DS(ON)
= 0.013
(for V
GS
= 4.5 V), and I
DMAX
= 10 A. Its SOA covers the 20 V,
4.0 A
DC
, and 4.5 A
PEAK
application requirements with adequate
margin.
Since the switching losses are negligible for properly driven
PFETs compared to conduction losses, the worst-case conduc-
tion losses can be estimated from the worst case ON resistance
(R
DS(ON)
) of the selected PFET when subjected to short circuit
current at the minimum input voltage and close to 100% duty
cycle. R
DS(ON)
increases about 50% at T
J
= 150
°
C. Thus the
worst case value we can use is 0.023
. The maximum PFET
dissipation is calculated as follows:
P
DMAX
=
I
PEAK
2
×
R
DS(ON)
= 4.5
A
2
×
0.023
= 0.47
W
Next the maximum junction temperature T
JMAX
of the transistor
can be calculated:
T
J
MAX
=
T
A
+ (
R
θ
J
A
)
×
P
DMAX
= 50 + (50)
×
0.47 = 74
°
C
where
T
A
= 50
°
C and
R
θ
J
A
= 50
°
C/W, as specified on the
transistor’s data sheet for a 1 inch square PCB-pad. The calcu-
lated
T
J
MAX
should be below the maximum allowed junction
temperature of the transistor with adequate margin. The
Si4463 specifies a T
JMAX
of 150
°
C, which we meet with more
than adequate margin.
I
V
T
L
s
H
A
LRMS
O
OFF
=
×
×
×
=
×
=
0 577
.
0 5
.
0 577
.
0 5 12 6 1 9
.
μ
24
0 3
.
.
.
μ
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ADP3802AR | Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.50V) 8-SM8 -40 to 110 |
| ADP3810 | Secondary Side, Off-Line Battery Charger Controllers(電池充電控制器) |
| ADP3811 | Secondary Side, Off-Line Battery Charger Controllers(電池充電控制器) |
| ADP667 | +5 V Fixed, Adjustable Low-Dropout Linear Voltage Regulator |
| ADP667AN | +5 V Fixed, Adjustable Low-Dropout Linear Voltage Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADP3801AR-REEL | 制造商:Rochester Electronics LLC 功能描述:SWITCH MODE DUAL CHARGER/LDO REGULATOR - Tape and Reel |
| ADP3802 | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Frequency Switch Mode Dual Li-Ion Battery Chargers |
| ADP3802AR | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Frequency Switch Mode Dual Li-Ion Battery Chargers |
| ADP3804 | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Frequency Switch Mode Li-Ion Battery Charger |
| ADP3804JRU | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Frequency Switch Mode Li-Ion Battery Charger |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。