QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
1
DESCRIPTION
Demonstration Circuit 1189 is a high efficiency USB
power manager with PowerPath
TM
control and Li-
ion/Polymer battery charger featuring the LTC
4088-1.
The LTC4088-1 includes a synchronous switching input
regulator, a full-featured battery charger and an ideal
diode. Designed specifically for USB applications, the
LTC4088-1’s switching regulator automatically limits its
input current to either 100mA, 500mA or 1A for wall-
powered applications via logic control.
The switching input stage provides power to VOUT
where power sharing between the application circuit and
the battery charger is managed. Charge current is auto-
matically reduced to maintain a regulated 3.6V VOUT
during low battery conditions. As the battery is charged,
VOUT tracks VBAT for high efficiency charging. This fea-
ture allows the LTC4088-1 to provide more power to the
application and eases thermal issues in constrained
applications.
An ideal diode ensures that system power is available
from the battery when the input current limit is reached
or if the USB or wall supply is removed.
The external P-
channel MOSFET supplements the internal ideal diode
by reducing R
ON
and increasing efficiency.
A CHRG LED indicates four possible states of the bat-
tery charger. Charging is indicated when the LED is
steady-ON. Not charging is indicated by a steady-OFF.
A NTC fault is indicated by a slow blinking rate
(1.5Hz) and a bad battery is indicated by a fast blink-
ing rate (6.1Hz).
The LTC4088-1 is available in the low profile 14-Lead
4mm
3mm
0.75mm DFN surface mount package.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Liner Technology Corporation.
Table 1. Typical Specifications (25
°
°°
°
C)
Input Voltage Range
, VBUS
4.35V to 5.5V
VOUT
3.5V to 4.7V (Mode and load dependent)
3.3V
Output Float Voltage V
BAT
(constant voltage mode)
4.2V
Output Charge Current I
BAT
(constant current mode)
0.5
A (R
PROG
equals 2
.00
K
Ω
)
QUICK START PROCEDURE
Refer to Table 1 for a listing of the inputs and outputs
of the 1189 Demo Circuit. Demo Circuit 1189 is best
evaluated using a Li-Ion/Polymer battery. When using
a battery simulator for evaluation, oscillations must
be
verified with a real battery at the same conditions
because it is difficult to match the impedance of a
real battery, which is required for battery charger
stability.
Refer to Figure 1 for the proper measurement and
equipment setup and follow the procedure below.
1. If using an external supply, connect a 0 to 6V,
1.5A supply with voltage adjusted to 0V be-
tween the VBUS and GND terminals. Connect a
Voltmeter across the VBUS and GND terminals.
If using the USB input option, have cable ready
to plug in when all loads and jumpers are set.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
2
Do not use the USB input and an external sup-
ply at the same time.
2. Set JP1, NTC jumper to INT to use the demo
board resistor. To use an external 100kOhm
NTC resistor, connect the NTC resistor between
J2-3 and the GND terminal. Then set the NTC
jumper to EXT.
3. Use Table 2 to set JP2, JP3, and JP4 (D0, D1,
and D2 respectively) to select the desired input
current limit and charger status.
TABLE 2. Controlled Input Current Limit
D0 D1 D2 CHARGER
I
LIM
0
0
0
OFF
100mA(1x
)
0
0
1
ON
100mA(1x)
0
1
0
OFF
500mA(5x)
0
1
1
ON
500mA(5x)
1
0
0
OFF
1A(10x)
1
0
1
ON
1A(10x)
1
1
0
OFF
2.5mA(Susp High)
1
1
1
OFF
500uA(Susp Low)
4. Connect a 0 to 2A adjustable load in series with
an ammeter between the VOUT terminal and the
GND terminal. Connect a Voltmeter between the
VOUT and GND terminals.
5. Connect a partially charged (~3.6V) Lithium ion
battery with the positive lead to the BAT termi-
nal and the negative lead to a GND terminal.
Connect the positive lead of a Voltmeter to the
BAT terminal and the negative lead to the GND
terminal. Connect the positive terminal of a
Voltmeter to PROG and the negative terminal to
GND to measure the current flowing into the
battery. The voltage on PROG will read 1 Volt
when the maximum charge current is reached.
The voltage on CLPROG will read 1.188 Volts
when the input current limit is reached. Ob-
serve VOUT.
See the datasheet for the proper values of I
BUSQ
and
h
CLPROG
in the 1X, 5X and 10X modes.
6. If using the USB input, plug in the USB cable
and observe the battery charge current and
VOUT. If using an external power supply, slowly
increase the supply and observe that the
LTC4088-1 starts to use the VBUS input power
as VBUS reaches 4.35V.
7. Discharge the battery to 2.5 volts. If Charger
mode is on, observe it is charging in trickle
charge mode and the charge current is 50mA.
As the battery voltage increases above 2.85V
observe that the charger goes into full constant
current mode. Observe that VOUT stays above
3.6V when the input current limit is not ex-
ceeded. Remove the NTC jumper on JP2. Ob-
serve the CHRG LED slow blinking rate. Also
observe the 35KHz pulse with varying duty cy-
cle between 4.7% and 95.3% on the
CHRG
terminal with an oscilloscope. Reinstall the NTC
jumper.
8. Increase the VOUT load and observe when the
input current starts to limit (V
CLPROG
=1.188 V).
When input current limit is reached, VOUT
drops from 300 mV above the BAT voltage to
15mV below the BAT voltage and the additional
load transitions to the battery through the ideal
diode. Due to the high efficiency of the switch-
ing regulator, the charge and load current may
be significantly above the input current depend-
ing on the voltage on the BAT pin.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
3
9. Repeat step 9 with different current limit
modes.
10. Set the VBUS input supply to 5V. Observe the
battery current as the battery voltage increases
above 4.1V. The Charge current starts to de-
crease as the battery voltage increases towards
4.2V.
See the latest LTC4088 data sheet for more infor-
mation on how this part performs.
APPLICATION INFORMATION
This demo circuit is designed to demonstrate the
full capability of the LTC4088-1 High Efficiency Bat-
tery Charger. Not all components are required in all
applications. The critical circuit components are on
the top of the board near the IC and listed in the
Required Circuit Components section of the Bill-of-
Materials below.
The input capacitor network of C7 and R13 is used
to dampen source lead inductances that commonly
occur in laboratory setups with twisted leads and a
bench power supply. When using an USB cable or
adaptor cable this input damping network will likely
not be required. Please note that the in-circuit ca-
pacitance of the specified 10uF, 0805 ceramic ca-
pacitor for C2 and C7 is approximately 5uF each at
a VBUS greater than 4.25 Volts.
Capacitor C4 is only required when using the 10X
mode. The LTC4088-1 requires a minimum of 10uF
on the VOUT pin in 10X mode for voltage loop sta-
bility. As an alternative to using two smaller X5R
capacitors, one larger X5R ceramic capacitor would
be acceptable, provided that the actual in-circuit
capacitance with 4.6 Volts applied is greater than
10uF.
Capacitor C5 is included to simulate a low imped-
ance battery. It is especially helpful when testing
the demo circuit with a battery simulator comprised
of a standard power supply with a 3.6 Ohm power
resistor across it. The leads connecting the power
supply to the demo circuit should be a twisted pair
to minimize lead inductance; although, even twisted
pairs can introduce enough inductance into the cir-
cuit to cause instability in the battery charger sec-
tion without the presence of C5. Capacitor C5 will
also provide proper operation of the circuit without
a battery present. Refer to the datasheet for more
discussion of operation without a battery. If de-
sired, it is possible to use a ceramic capacitor in
series with a low valued resistor to stabilize the bat-
tery charger when no battery is present. Please
refer to the datasheet for the suggested capacitor
and resistance range.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
4
Figure 1. Proper Measurement Equipment Setup for DC1189A
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1189A
HIGH EFFICIENCY BATTERY CHARGER/USB POWER MANAGER
WITH REGULATED OUTPUT VOLTAGE
LTC4088-1
6