ISL6255AHRZ Intersil, ISL6255AHRZ Datasheet - Page 18

• Manufacturer Part Number: ISL6255AHRZ
• Description: IC BATTERY CHRGR NOTEBOOK 28-QFN
• Manufacturer: Intersil

Specifications of ISL6255AHRZ

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 7 V ~ 25 V
• Operating Temperature: -10°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 28-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Loop Compensation Design
ISL6255, ISL6255A uses a constant frequency current mode
control architecture to achieve fast loop transient response.
An accurate current sensing resistor in series with the output
inductor is used to regulate the charge current, and the
sensed current signal is injected into the voltage loop to
achieve current mode control to simplify the loop
compensation design. The inductor is not considered as a
state variable for current mode control and the system
becomes a single order system. It is much easier to design a
compensator to stabilize the voltage loop than voltage mode
control. Figure 17 shows the small signal model of the
synchronous buck regulator.
PWM Comparator Gain F
The PWM comparator gain Fm for peak current mode
control is given by:
Power Stage Transfer Functions
Transfer function F
Where
M
F
1
( )
R8, R11
=
PARTS
Q1, Q2
Q3, Q4
S
R10
R12
R13
Q5
Q6
R1
R2
R3
R4
R5
R6
R7
R9
--------- .
V
L
11
=
IN
v ˆ
ω
d ˆ
o
esr
TABLE 2. COMPONENT LIST (Continued)
=
V
=
10 μ H/3.8A/26m Ω , Sumida, CDRH104R-100
30V/35m Ω , FDS6912A, Fairchild
-30V/30m Ω , SI4835BDY, Siliconix
Signal P-channel MOSFET, NDS352AP
Signal N-channel MOSFET, 2N7002
40m Ω , ±1%, LRC-LR2512-01-R040-F, IRC
20m Ω , ±1%, LRC-LR2010-01-R020-F, IRC
18 Ω , ± 5%, (0805)
2.2 Ω , ± 5%, (0805)
100k Ω , ± 5%, (0805)
10k, ± 5%, (0805)
100 Ω , ± 5%, (0805)
130k, ± 1%, (0805)
10.2k Ω , ± 1%, (0805)
4.7 Ω , ± 5%, (0805)
20k Ω , ± 1%, (0805)
1.87k Ω , ± 1%, (0805)
in
R
c
ω
S
1
C
PART NUMBERS AND MANUFACTURER
o
2
2
o
1
1
(S) from control to output voltage is:
+
,
+
ω
Q
ω
o
p
S
S
esr
Q
≈
p
R
+
o
18
m
1
C
:
L
o
,
ω
o
=
LC
1
o
ISL6255, ISL6255A
+
+
+
+
Transfer function F
Current loop gain T
equation:
where R
usually equal to the product of the charging current sensing
resistance and the gain of the current sense amplifier, CA2.
For ISL6255, ISL6255A, R
The voltage gain with open current loop is:
Where
error amplifier. The Voltage loop gain with current loop
closed is given by:
If T
From the above equation, it is shown that the system is a
single order system, which has a single pole located at
before the half switching frequency. Therefore, simple type II
compensator can be easily used to stabilize the system.
T
T
L
F
L
i ˆ
i ˆ
i ˆ
i ˆ
i ˆ
i ˆ
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
in
in
in
in
in
in
V
i
v
v
in
in
in
in
in
in
0.25V
0.25V
2
FIGURE 17. SMALL SIGNAL MODEL OF SYNCHRONOUS
( )
( )
( )
S
(
( )
S
i
S
S
S
(S)>>1, then it can be simplified as follows:
)
=
=
=
=
=
CA2
CA2
K =
i ˆ
1
d ˆ
0.25 R
T
L
KM F
4 V
-------------- -
T
+
11/Vin
11/Vin
I
I
I
I
I
I
V
is the trans-resistance in current loop. R
L
L
L
L
L
L
v
=
T
d ˆ
d ˆ
d ˆ
d ˆ
d ˆ
d ˆ
V
O
F B
( )
V
i
S
R
+
+
FB
-
-
( )
o
BUCK REGULATOR
S
1
o
(
----------------------------- -
T
1:D
1:D
1:D
1:D
V
( )A
d ˆ
d ˆ
d ˆ d ˆ
d ˆ d ˆ
R
F
S
+
in
, V
O
2
R
R
( )M
+
2
S
FB
L
i
(S) is expressed as the following
V
T
(S) from control to inductor current is:
R
( )
V
V
V
V
V
V
ω
S
S
L
in
in
in
in
in
in
is the feedback voltage of the voltage
o
)
2
2
d ˆ
d ˆ
d ˆ
d ˆ
d ˆ
d ˆ
----------------------- - A
1
1
+
1
T
+
+
ω
+
= 20R
i ˆ
i ˆ
i ˆ
i ˆ
i ˆ
i ˆ
ω
o
----------- -
ω
L
L
L
L
L
L
T
T
T
T
S
S
-------
ω
Q
S
S
z
esr
i
i
i
i
(S)
(S)
(S)
(S)
P
p
L
L
L
L
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
+
comp
comp
comp
comp
comp
comp
1
V
1
.
( )
S
, where
V
V
R
R
R
R
CA2
CA2
,
T
T
T
T
-Av(S)
-Av(S)
-Av(S)
-Av(S)
ω
P
≈
---------------- -
R
ω
O
z
Rc
Rc
Rc
Rc
Co
Co
1
C
≈
Ro
Ro
Ro
Ro
O
T
T
T
T
T
May 23, 2006
R
v
v
v
v
is
(S)
(S)
o
(S)
(S)
1
FN9203.2
C
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
v ˆ
o
ω
o
o
o
o
o
o
.
p
K
K
K
K