DC1550A - Demo Manual

QUICK START GUIDE FOR
DC1550A
LTC3553EPD: Micropower USB
Power Manager with Li-Ion Charger,
Buck DC/DC, and LDO Regulator
DESCRIPTION
Demonstration Circuit DC1550A is a Micropower USB Power Manager with Li-Ion Charger, Buck DC/DC, and LDO
Regulator featuring the LTC®3553.
PERFORMANCE SUMMARY Specifications are at TA = 25°C
SYMBOL
VBUS
V(BAT)
I(BAT)
VLDO
VBUCK
PARAMETER
Bus Input Voltage Range
Battery Float Voltage
Battery Charge Current
LDO Output Voltage
Buck Regulator Output Voltage
CONDITIONS
Constant Voltage Mode
Constant Current Mode, RPROG = 1.87k
I(VLDO) ≤ 200mA
I(VBUCK) ≤ 200mA
MIN
4.35
4.15
420
3.25
1.15
TYP
MAX
6
4.23
500
3.35
1.25
UNITS
V
V
mA
V
V
QUICK START PROCEDURE
Refer to Figure 1 for the proper measurement
equipment setup and jumper settings and follow the
procedure below.
NOTE. When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscilloscope
probe. Measure the input or output voltage ripple by touching the
probe tip directly across the VBUS or VOUT(x) and GND terminals.
See Figure 2 for proper scope probe technique.
1. Set PS1 = 0V, PS2 = 3.6V. Press “ON” button
for > 0.5s. Observe I(BAT) (AM2), VBUCK
(VM5) and VLDO (VM6).
The LTC3553 is in STBY which reduces the battery current to less than 15μA, even with both
regulators running. In STBY the maximum current from regulators is reduced to as low as
10mA
2. Set STBY (JP6) to “OFF”, PS1 to 5V. Observe
I(VBUS) (AM1), I(BAT) (AM2) and VPROG
(VM2).
The LTC3553 is now operating in normal mode
drawing more current from the battery. However
the regulators are now capable of delivering over
200mA each. Also, since VBUS is now available,
the battery charger is operating, but charge current is limited by the input current limit to
100mA.
3. Set HPWR (JP2) to “500mA”. Observe I(VBUS)
(AM1), I(BAT) (AM2) and VPROG (VM2).
The input current limit is now 500mA, so the battery charger is delivering ~420mA to the battery.
4. Set LD2 to 200mA, LD3 to 200mA. Observe
VBUCK (VM5), VLDO (VM6) and I(BAT) (AM2).
Each regulator is supplying 200mA, and since
the efficiency is ~90%, drawing ~225mA. So,
the battery charger is only delivering approximately 50mA. This is because the input current
limit is 500mA – 225mA – 225mA = 50mA.
1
LTC3553EPD
5. Set LD2 to 0A, LD3 to 0A. Press “OFF” button.
Observe VBUCK (VM5) and VLDO (VM6).
The regulators are now off and therefore supplying 0 current. The battery charger is once again
supplying ~ 420mA to the battery.
6. Reset the Jumpers to their default position.
2
LTC3553EPD
VM2
+
-
VM3
AM1
-
+
PS1
1A
+
+
4.35V - 5.5V supply
-
+
-
+
VM1
-
AM2
+
3.6Ω
+
VM4
-
-
+
1A
-
+
+
AM3
LD2
0V - 5V
VM5
-
+
2A
AM4
+
PS2
0V - 5V supply
+
-
LD3
0V - 5V
VM6
-
2A
Note: All connections from equipment should be Kelvin connected directly to the board
pins which they are connected on this diagram and any input or output leads should be
twisted pair.
Figure 1. Proper Measurement Equipment Setup for DC1550A
GND
VIN
Figure 2. Measuring Input or Output Ripple
3
LTC3553EPD
Figure 3. Circuit Schematic
4
LTC3553EPD
Figure 4. Bill of Materials
5
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