DEMO MANUAL DC1721A-A
LTC4000EGN/LTC3789EGN
14.6V, 5A Battery Charger with 6V
IN
to 36V
IN
Buck-Boost Converter
DESCRIPTION
Demonstration circuit 1721A-A is a 14.6V, 5A battery
charger and PowerPath™ manager with 6V
IN
to 36V
IN
buck-boost converter featuring the LTC
®
4000/LTC3789,
targeted at 4-cell LiFePO
4
applications. The output of this
demo board was specifically tailored for a Tenergy 10A-
hour battery, P/N 30207. Other voltages can be set by
changing R
OFB2
and R
BFB2
. The desired nominal voltage
can be accurately trimmed by using trim resistors R42 and
R43. For example, for 14.4V battery float voltage, change
R
OFB2
and R
BFB2
to 86.6k, and add 7.5M at R42 and R43
for greater set point accuracy.
This circuit was designed to demonstrate the high levels of
performance, efficiency, and small solution size attainable
using these parts in a buck-boost converter battery charger,
intelligent PowerPath manager, and power supply. It oper-
ates at 400kHz and produces a regulated 5A/14.6V battery
charger output as well as a system output of up to 6.25A
from an input voltage range of 6V to 36V: suitable for a
wide variety of portable applications including instruments,
industrial equipment, power tools, and computers. It has
a total footprint area of 12.4cm
2
(3.6cm
2
for the LTC4000
circuit only). Synchronous rectification helps to attain
efficiency exceeding 96% at full load and nominal input.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
PERFORMANCE SUMMARY
SYMBOL
V
IN
I
IN
V
FLOAT
I
BAT
V
OUT_SYS
I
OUT_SYS
f
SW
V
OUT_SYS_P-P
P
OUT
/P
IN
PARAMETER
Input Supply Range
Input Current Limit
Battery Float Voltage
Output Regulation
Battery Charge Current
System Output Voltage
System Output Current Range
Switching (Clock) Frequency
System Output Ripple
System Output Efficiency (See Figure 3)
Approximate Size
(T
A
= 25°C)
CONDITIONS
MIN
6
11
14.4
Line and Load (6V to 36V, 0A to 5A)
12.3
0
400
V
IN
= 24V, I
OUT_SYS
= 5A (20MHz BW)
V
IN
=24V, I
OUT_SYS
= 5A
Component Area
×
Top Component Height
50
96.5
12.4cm
2
×
0.40cm
14.6
±0.05
5
14.6
15.5
6.25
14.8
TYP
MAX
36
UNITS
V
A
V
%
A
V
A
kHz
mV
P-P
%
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DEMO MANUAL DC1721A-A
QUICK START PROCEDURE
Demonstration circuit 1721 is easy to set up to evaluate the
performance of the LTC4000/LTC3789. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
WARNING: BATTERIES ARE POTENTIALLY DANGEROUS
HIGH ENERGY SOURCES. IMPROPER CONNECTION,
OVERCHARGE, OR RAPID DISCHARGE COULD RESULT
IN EXPLOSION AND/OR FIRE.
NOTE: When measuring the output voltage ripple, care must
be taken to avoid a long ground lead on the oscilloscope
probe. Measure the output voltage ripple by touching the
probe tip and ground ring directly across the last output
capacitor as shown in Figure 1.
1. Connect a low ESR electrolytic capacitor to the BAT
output (≥1800μF at ≥20V).
NOTE: This capacitor helps simulate the low imped-
ance of a battery and maintain stability of the charge
current loop. It is only needed for test purposes with
electronic or resistive loads, and not needed in the
actual application (where the load is a battery).
2. Set MODE jumper to CCM. Set CHARGE jumper to
DISABLE.
3. Set an input power supply that is capable of 6V to 36V
and 12A to 24V. Then turn off the supply.
4. With power off, connect the supply to the input terminals
V
IN
and GND.
NOTE:
a. Input voltages lower than 6V can keep the converter
from turning on due to the undervoltage lockout
feature of the LTC4000.
b. If efficiency measurements are desired, refer to
Figure 1 for test setup.
5. Turn on the power at the input.
NOTE: Make sure that the input voltage never
exceeds 36V.
6. Check for the proper V
OUT_SYS
of 15.3V. Turn off the
power at the input.
7. Once the proper output voltages are established, con-
nect a variable load capable of sinking 7A at 16V to the
output terminals V
OUT_SYS
and GND. Set the current
for 0A.
8. Turn on the power at the input.
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
9. Once the proper V
OUT_SYS
is again established, adjust
the load and/or source within the operating range and
observe the output voltage regulation, ripple voltage,
efficiency, input and output current limit, and other
desired parameters.
10. Turn off the power at the input.
11. Connect the output load and meters to the BAT output.
12. Set CHARGE jumper to ENABLE.
13. Turn on the power at the input.
14. Once the proper V
OUT_SYS
is again established, adjust
the load and/or source within the operating range and
observe the battery float voltage regulation and other
desired parameters.
15. Set the load to constant voltage mode to more easily
observe charge current and trickle charge current.
NOTE: Operation in the instant-on region (V
OUT
< 12.5V)
may engage thermal limit circuit to protect Q7 in linear
region.
NOTE: The optional thermal limit circuit for Q6 (Q9,
RNTC3, R55-R59, and U4) is included to protect Q6 in
case of an extended short-circuit on V
OUT_SYS
under
adverse thermal conditions (T
A
> 40°C). It may not be
needed in applications with less severe thermal condi-
tions, lower current available to V
OUT_SYS
, or where
continuous short circuit protection on V
OUT_SYS
is not
required.
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DEMO MANUAL DC1721A-A
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
Figure 2. Proper Noise Measurement Setup
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3
DEMO MANUAL DC1721A-A
QUICK START PROCEDURE
100
95
EFFICIENCY (%)
90
85
80
0.5
V
IN
= 6V
V
IN
= 15V
V
IN
= 24V
V
IN
= 36V
1.5
2.5
3.5
I
OUT
(A)
4.5
5.5
dc1721aa F03
Figure 3. Efficiency from V
IN
to V
OUT_SYS
LTC4000 / LTC3789 SYSTEM BLOCK DIAGRAM
VIN
VOUT-SYS
Rsense-input
LTC3789
DC - DC CONVERTER
+
+
ITH
CC1
RC1
CC2
Gm
Rsense-charge
BAT
10nF
A10
LTC4000
A9
Gm
GND
NOT ON THE BOARD
A5
Gm
A8
Gm
A7
Gm
A4
A6
Figure 4. Block Diagram
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DEMO MANUAL DC1721A-A
PARTS LIST
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
QTY
2
2
3
3
2
2
2
1
4
2
4
1
1
1
1
1
2
1
2
2
1
1
1
1
1
2
2
2
1
3
2
1
1
1
REFERENCE
CL, CBAT
C24, CBIAS
CC2, C14, CTMR
CIIMON, CIBMON, C19
C15, CIN
CIN1, CIN2
COUT1, COUT2
CSS
C1, C2, C16, C17
C4, C22
C5, C6, C9, C25
C10
C12
C13
C18
C33
C34, C35
D2
D4, D7
D5, D6
D9
D10
F1
LED2
L1
Q2, Q4
Q3, Q5
Q6, Q7
Q8
ROFB1, RBFB1, R45
ROFB2, RBFB2
RCL
RIL
RCS
PART DESCRIPTION
Capacitor, X5R, 2.2μF 25V, 20%, 0805
,
Capacitor, X7R, 1μF 16V, 10%, 0603
,
Capacitor, X7R, 0.1μF 50V, 10%, 0603
,
Capacitor, C0G, 1000pF 25V, 5%, 0603
,
Capacitor, X7R, 1μF 50V, 10%, 1210
,
Capacitor, Alum, HVH, 56μF 50V
,
Capacitor, OS-CON, 150μF 20V, 20%
,
Capacitor, X7R, 0.022μF 50V, 10%, 0603
,
Capacitor, X5R, 22μF 25V, 10%, 1210
,
Capacitor, X7R, 0.22μF 16V, 10%, 0603
,
Capacitor, X7R, 3.3μF 50V, 10%, 1210
,
Capacitor, X5R, 2.2μF 6.3V, 20%, 0603
,
Capacitor, NPO, 390pF 100V, 5%, 1206
,
Capacitor, NPO, 1.8nF 100V, 5%, 1206
,
Capacitor, X7R, 10μF 10V, 10%, 1206
,
Capacitor, X5R, 4.7μF 10V, 20%, 0603
,
Capacitor, X7R, 10nF 25V, 5%, 0603
,
Diode, Switch, 75V, 350mW, SOT23-3
Diode, Schottky, 1A, 60V, POWERDI123
Diode, Schottky, 40V, 2A, SMA
Diode, Zener, SM, BZT52C3V0, SOD323
Diode, Zener, 5.6V, 500mW, SOD123
FUSE, 6.3A 32V, T-Lag, 1206, SMD
LED, Dual Red/Green
Inductor, 4.7μH
MOSFET N-Channel, 40V, POWERPAK-8
MOSFET N-Channel, 20V, POWERPAK-8
MOSFET P-Channel, 30V, 1206-8 ChipFET
Small Signal MOSFET
Resistor, Chip, 1M, 0.1W, 1%, 0603
Resistor, Chip, 84.5k, 0.1W, 1%, 0603
Resistor, Chip, 24k, 0.1W, 5%, 0603
Resistor, Chip, 18.2k, 0.1W, 1%, 0603
Sensor Resistor, 0.01Ω, 1W, 2%, 1508 SMD
MANUFACTURER/PART NUMBER
AVX, 08053D225MAT2A
AVX, 0603YC105KAT2A
AVX, 06035C104KAT2A
AVX, 06033A102JAT2A
AVX, 12105C105KAT2A
Sun Electronics, 50HVH56M
Sanyo, 20SVP150M
AVX, 06035C223KAT2A
AVX, 12103D226KAT2A
Taiyo Yuden, EMK107BJ224KA
AVX, 12105C335KAT2A
AVX, 06036D225MAT2A
AVX, 12061A391JAT2A
AVX, 12061A182JAT2A
AVX, 1206ZC106KAT2A
AVX, 0603ZD475MAT2A
AVX, 06033C103JAT2A
Diode Inc., BAS16-7-F
Diode Inc., DFLS160-7
Diode Inc., B240A-13-F
Diodes, BZT52C3V0
Diode Inc., BZT52C5V6
Cooper Bussman, 3216TD6.3-R
LiteOn, LTST-C155KGJRKT
Toko, FDA1254-4R7M
Vishay, SiR422DP-T1-GE3
Vishay, SiR496DP-T1-GE3
Vishay, Si7135DP
On Semi, 2N7002LT1G
Vishay, CRCW06031M00FKEA
Vishay, CRCW060384K5FKEA
Vishay, CRCW060324KJKEA
Vishay, CRCW060318K2FKEA
Susumu, RL3720WT-R010-G
Required Circuit Components
dc1721aaf
5
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