LTC3789 LINER [Linear Technology], LTC3789 Datasheet - Page 28

• Manufacturer Part Number: LTC3789
• Description: High Voltage High Current Controller for Battery Charging and Power Management
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
LTC4000
• The charge termination time is set at 2.9 hours accord-
• The C/X current termination level is programmed at 1A
• The output voltage regulation level is set at 12V accord-
• The instant-on voltage level is consequently set at 9.79V
28
ing to the following formula:
according to the following formula:
Note that in this particular solution, the timer termina-
tion is selected since a capacitor connects to the TMR
pin. Therefore, this C/X current termination level only
applies to the CHRG indicator pin.
ing to the following formula:
according to the following formula:
The worst-case power dissipation during instant-on
operation can be calculated as follows:
• During trickle charging:
• And beyond trickle charging:
Therefore, depending on the layout and heat sink avail-
able to the charging PMOS, the suggested PMOS over
temperature detection circuit included in Figure 7 may
need to be included. For the complete application circuit,
please refer to Figure 25.
R
R
C
V
INST _ ON
TMR
CX
OFB1
P
P
INST _ ON
TRKL
=
(nF) = t
=
(
1A • 5mΩ
⎛
⎜
⎝
= 0.86 • 10.8
= 9.3W
= 0.86 • V
1.193
=
[
[
12
= 0.86 • 10.8 – 7.33
= 19.3W
1150kΩ + 127kΩ
= 0.86 • V
TERMINATE
0.25µA
[
[
− 1
)
127kΩ
+ 0.5mV
⎞
⎟ • 127kΩ ≈ 1.15MΩ
⎠
FLOAT
]
(h) • 34.6 = 2.9 • 34.6 = 100nF
FLOAT
• 1A
– V
≈ 22.1kΩ
BAT
– V
• 0.974V = 9.79V
BAT
]
]
• I
• 10A
CLIM _ TRKL
]
• I
CLIM
• The range of valid temperature for charging is set at
• For compensation, the procedure described in the
Figure 15. Charge Current Regulation Loop Compensation Setup
B
–1.5°C to 41.5°C by picking a 10k Vishay Curve 2 NTC
thermistor that is thermally coupled to the battery, and
connecting this in series with a regular 10k resistor to
the BIAS pin.
empirical loop compensation section is followed. As
recommended, first a 1µF C
sets all the loops to be stable. For an example of typical
transient responses, the charge current regulation loop
when V
Figure 15 shows the recommended setup to inject a
DC-coupled charge current variation into this particular
loop. The input to the CL pin is a square wave at 70Hz
with the low level set at 120mV and the high level set
at 130mV, corresponding to a 1.2A and 1.3A charge
current (100mA charge current step). Therefore, in this
particular example the trickle charge current regulation
stability is examined. Note that the nominal trickle
charge current in this example is programmed at 1.25A
(R
CL
A
= 24.9kΩ).
OFB
is regulated to V
1500pF
10k
C
OUT(INST_ON)
0.015µF
and 10k R
SQUARE WAVE
GENERATOR
f = 60Hz
1k
C
is used, which
is used here.
IBMON
CL
LTC4000
4000 F15
4000f