MAX8765ETI Maxim Integrated, MAX8765ETI Datasheet - Page 22
MAX8765ETI
Manufacturer Part Number
MAX8765ETI
Description
Battery Management
Manufacturer
Maxim Integrated
Series
MAX1908, MAX8724, MAX8765, MAX8765Ar
Datasheet
1.MAX8765ETI.pdf
(30 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
MAX8765ETI
Manufacturer:
MAXIM
Quantity:
276
Company:
Part Number:
MAX8765ETI+
Manufacturer:
Maxim Integrated Products
Quantity:
135
Company:
Part Number:
MAX8765ETI+T
Manufacturer:
MAXIM
Quantity:
5 442
MAX1908/MAX8724/MAX8765/MAX8765A
22
Compensation of the CCV loop depends on the para-
meters and components shown in Figure 5. C
R
series resistor. R
(ESR) of the charger output capacitor (C
equivalent charger output load, where R
I
amplifier, R
transconductance, GMV = 0.125µA/mV. The DC-DC
converter transconductance, GM
where A
sense resistor in the Typical Application Circuits .
The compensation pole is given by:
The compensation zero is given by:
The output pole is given by:
Low-Cost Multichemistry Battery Chargers
Figure 5. CCV Loop Diagram
CHG
CV
are the CCV loop compensation capacitor and
. The equivalent output impedance of the GMV
CCV
CSI
R
C
CV
CV
= 20, and RS2 is the charging current-
OGMV
f
P CV
f
f
P OUT
GM
_
Z CV
ESR
R
_
_
OGMV
OUT
≥ 10MΩ. The voltage amplifier
GM
is the equivalent series resistance
=
GMV
=
OUT
2π
=
=
2π
R
2π
A
OGMV
R
CCV Loop Definitions
R
CSI
CV
L
1
1
×
REF
1
1
×
×
OUT
C
×
C
RS
BATT
OUT
C
CV
2
CV
= 3.33A/V:
C
OUT
R
ESR
OUT
L
). R
= V
CV
R
L
L
BATT
is the
and
/
where R
Output zero due to output capacitor ESR:
The loop transfer function is given by:
Assuming the compensation pole is a very low
frequency, and the output zero is a much higher fre-
quency, the crossover frequency is given by:
To calculate R
Cells = 4
C
V
I
GMV = 0.125µA/mV
GM
R
f = 400kHz
Choose crossover frequency to be 1/5th the
MAX1908’s 400kHz switching frequency:
Solving yields R
Conservatively set R
frequency at:
Choose the output-capacitor ESR so the output-capacitor
zero is 10 times the crossover frequency:
CHG
BATT
OGMV
OUT
OUT
= 2.5A
= 22µF
= 16.8V
f
LTF GM
CO CV
L
= 10MΩ
= 3.33A/V
R
f
varies with load according to R
ESR
Z ESR
_
_
f
=
CO CV
CV
(
=
(
f
1
1
Z ESR
_
+
=
CV
2
+
_
=
and C
OUT
π
sC
sC
GMV R
2
×
= 26kΩ.
π
=
CV
10
OUT
CV
f
R
CO_CV
×
GMV R
=
ESR
CV
R
×
×
×
= 1kΩ, which sets the crossover
2
2π
L
f
R
CO CV
×
π
values of the circuit of Figure 2:
1
×
CV
OGMV
C
×
R
R
×
1
GMV R
_
ESR
= 3kHz
C
ESR
2π
OUT
×
OUT
CV
C
GM
1
)
)
OUT
×
(
×
×
1
(
1
×
C
C
+
=
OUT
+
GM
OUT
OUT
OGMV
sC
2 412
sC
.
L
CV
OUT
OUT
=
= V
=
80
MHz
×
Maxim Integrated
×
0 24
.
BATT
R
kHz
×
CV
R
Ω
L
)
/I
)
CHG.