MAX8724ETI+ Maxim Integrated Products, MAX8724ETI+ Datasheet - Page 23

• Manufacturer Part Number: MAX8724ETI+
• Description: IC CHARGER BATTERY 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8724ETI+

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 8 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-WFQFN Exposed Pad
• Product: Charge Management
• Operating Supply Voltage: 2.5 V to 3.6 V
• Supply Current: 400 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Charge Safety Timers: Yes
• Mounting Style: SMD/SMT
• Temperature Monitoring: No
• Uvlo Start Threshold: 7 V
• Uvlo Stop Threshold: 7.85 V
• Case: QFN
• Dc: 05+
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The 22µF ceramic capacitor has a typical ESR of
0.003Ω, which sets the output zero at 2.412MHz.
The output pole is set at:
where:
Set the compensation zero (f
the output pole (f
ing a pole-zero cancellation and maintaining a single-
pole system response:
Choose C
zero (f
Figure 6. CCV Loop Gain/Phase vs. Frequency
Z_CV
f
f
CV
P CV
P OUT
) at 1.6kHz. This sets the compensation pole:
C
Low-Cost Multichemistry Battery Chargers
_
_
R
-20
-40
-60
CV
80
60
40
20
= 100nF, which sets the compensation
0
L
f
Z CV
1
=
=
=
P_OUT
_
______________________________________________________________________________________
=
2
∆
2
∆
π
V
π
2
I
10
CHG
R
BATT
R
π
=
CV
R
OGMV
2π
= 1.08kHz), effectively produc-
L
CCV LOOP GAIN
vs. FREQUENCY
100
×
×
1
FREQUENCY (Hz)
1
1
R
=
1 08
C
CV
.
Battery ESR
Z_CV
×
OUT
1
C
1k
kHz
×
CV
C
) so it is equivalent to
=
CV
10k
=
1 08
=
.
147
0 16
.
100k
kHz
nF
Hz
1M
Compensation of the CCI loop depends on the parame-
ters and components shown in Figure 7. C
loop compensation capacitor. A
of the current-sense amplifier. RS2 is the charge cur-
rent-sense resistor, RS2 = 15mΩ. R
lent output impedance of the GMI amplifier ≥ 10MΩ.
GMI is the charge-current amplifier transconductance
= 1µA/mV. GM
ductance = 3.3A/V. The CCI loop is a single-pole sys-
tem with a dominant pole compensation set by f
The loop transfer function is given by:
Since:
The loop transfer function simplifies to:
LTF GM
-105
-120
-135
-45
-60
-75
-90
=
1
OUT
10
LTF GMI
OUT
f
P CI
GM
×
_
CCV LOOP PHASE
=
vs. FREQUENCY
100
A
FREQUENCY (Hz)
OUT
is the DC-DC converter transcon-
CSI
=
2π
1k
×
×
=
RS
R
1
A
OGMI
+
2
10k
CSI
CCI Loop Definitions
sR
×
1
R
GMI
OGMI
1
×
CSI
OGMI
100k
×
RS
C
1
OGMI
is the internal gain
2
CI
+
×
sR
1M
C
R
CI
OGMI
is the equiva-
OGMI
CI
is the CCI
×
P_CI
C
CI
:
23