参数资料
型号: ADP3802AR
厂商: ANALOG DEVICES INC
元件分类: 电源管理
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
封装: SOIC-16
文件页数: 15/20页
文件大小: 256K
代理商: ADP3802AR
ADP3801/ADP3802
–15–
REV. 0
The efficiency of this circuit is shown in Figure 26 for a charge
current of 4 Amps. As expected, the efficiency increases with the
output voltage, up to a maximum of 92% at 12.6 V.
OUTPUT – Volts
6
7
8
9
10
12
11
E
60
13
14
VCC = 15V
I
CHARGE
= 4 AMP
FREQ = 200kHz
FREQ = 500kHz
100
70
80
90
Figure 26. Efficiency for I
CHARGE
= 4.0 Amp
Figure 27 shows the output voltage transient when a battery
load is snapped off. The output is charging a battery (which is
currently discharged to 5 V) at 4.0 A when the battery is re-
moved. The high charge current causes the output voltage to
quickly increase and exceed the final battery voltage. However,
the overvoltage comparator quickly controls the output and only
a small overshoot results. When the battery is returned to the
circuit, VBAT is pulled back down to the battery’s voltage.
TIME – ms
2.00V
O
6V
8V
10V
12V
14V
CH1
M50.0ms
CH 1
10.0V
V
BAT
= 12.6V
I
= 4 AMP
VCC = 15V
50ms/DIV
Figure 27. Output Voltage Transient Due to Battery Snap
Off
The behavior of the circuit when it is powered on with a dead
battery inserted is important to check to make sure that the
charger does not exhibit irregular behavior during power-up. In
this case, the ADP3801 needs to regulate the output current to
4.0 A. Figure 28 shows the average Si4463 source current
under such a condition. When the input power is applied to the
charger, the source current ramps up in a controlled manner
due to the ADP3801’s soft start.
I
C
5V
10V
15V
VCC = 15V
T
A
= +25
8
C
I
= 4 Amps
20ms/DIV
I
CHARGE
(AVERAGE)
VCC
4A
0A
V
C
Figure 28. Source Current Due to Input Turn-On
Feedback Loop Compensation Design
The ADP3801 and ADP3802 have two separate feedback loops,
the current control loop and the voltage control loop. Each loop
must be compensated properly so that the circuit is stable dur-
ing the entire charging cycle of a battery including the case where
no battery is present. A series RC from the COMP pin to ground
provides pole/zero compensation for both loops. The circuit in
Figure 24 is properly compensated for the ADP3801 and
ADP3802 and can be used as is.
Figure 29 shows a typical ac model of the ADP3801/ADP3802.
The current loop and voltage loop are comprised of voltage
controlled current sources (GM stages). The gains given in the
schematic and the impedance at the COMP node are typical
values for both the ADP3801 and ADP3802. This model can be
used to simulate the small signal ac behavior of the part using a
SPICE-based simulator when paired with an ac model of a buck
regulator. However, transient and dc behavior is not modeled
with this model. The GM stages are actually modeled using the
“Table” component in PSpice, which limits the dc levels to ease
dc convergence. The coefficients on the schematic give the table
coefficients. The input resistors (R1 and R2) are currently set
for a 4.2 V final battery voltage. Use the accompanying table to
adjust R1 and R2 for the other voltage options. Doing so is
important to properly set the voltage loop gain.
GM2
CS+
V1
1.65V
gm = 8E – 3
(–12.5m, –200E – 6) (12.5m,0)
I1
100
m
A
GM3
GM1
CS–
4.2V 173k
V
112k
V
8.4V 229k
V
56k
V
12.6V
247.7k
V
37.3k
V
V
BAT
R1
R2
R3
100k
V
R2
112k
V
R1
173k
V
V
BAT
gm = 1.6E – 3
(–62.5m, –200E – 6) (62.5m,0)
GAIN = 1V/V
OUT
E4
R4
4M
V
gm = 1E – 4
(0,0) (0.2, 20E – 6)
ISET
Figure 29. AC Behavioral SPICE Model for the ADP3801
and ADP3802
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