DC1459B - Demo Manual

DEMO CIRCUIT 1459B
LTC3588EMSE-1/-2
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LTC3588EMSE-1
LTC3588EMSE-2
Piezoelectric Energy
Harvesting Power Supply
DESCRIPTION
Demonstration Circuit 1459B is an energy harvesting
power supply featuring the LTC3588-1/LTC3588-2.
The LTC3588 integrates a low-loss full-wave bridge
with a high efficiency buck converter to form a complete energy harvesting solution optimized for high
output impedance energy sources such as piezoelectric transducers. An ultralow quiescent current undervoltage lockout mode with a wide hysteresis window
allows charge to accumulate on an input capacitor
until the buck converter can efficiently transfer a portion of the stored charge to the output. Four output
voltages are pin selectable with up to 100mA of continuous output current. A power good comparator
produces a logic high referenced to VOUT on the
PGOOD pin when the converter reaches the programmed VOUT, signaling that the output is in regulation.
The LTC3588EMSE-1/LTC3588EMSE-2 are available
in a 10-lead (3mm × 3mm) MSE surface mount package with exposed pad.
L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered
trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy
Drive, FilterCAD, Hot Swap, LinearView, µModule, Micropower SwitcherCAD, Multimode
Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No RSENSE, Operational Filter, PanelProtect,
PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT,
UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names
may be trademarks of the companies that manufacture the products.
TABLE 1
PERFORMANCE SUMMARY LTC3588EMSE-1 Specifications are at TA = 25°C
SYMBOL
VIN
VOUT 1.8V
VOUT 2.5V
VOUT 3.3V
VOUT 3.6V
PARAMETER
Input Voltage Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
CONDITIONS
D0 = 0, D1=0
D0 = 1, D1=0
D0 = 0, D1=1
D0 = 1, D1=1
MIN
4.3
1.71
2.425
3.201
3.491
to
to
to
to
MAX
18.0
1.89
2.575
3.399
3.708
UNITS
V
V
V
V
V
PERFORMANCE SUMMARY LTC3588EMSE-2 Specifications are at TA = 25°C
SYMBOL
VIN
VOUT 3.45V
VOUT 4.1V
VOUT 4.5V
VOUT 5.0V
PARAMETER
Input Voltage Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
Output Voltage Range
CONDITIONS
D0 = 0, D1=0
D0 = 1, D1=0
D0 = 0, D1=1
D0 = 1, D1=1
MIN
14.0
3.346
3.977
4.365
4.850
to
to
to
to
MAX
18.0
3.554
4.223
4.635
5.150
UNITS
V
V
V
V
V
1
LTC3588EMSE-1/-2
OPERATING PRINCIPLE
Refer to the block diagram within the LTC3588-1/-2
data sheet for its operating principle.
The LTC3588 is an ultralow quiescent current power
supply designed specifically for energy harvesting
and/or low current step-down applications. The part
is designed to interface directly to a piezoelectric or
alternative A/C energy source, rectify and store the
harvested energy on an external capacitor, bleed off
any excess energy via an internal shunt regulator,
and maintain a regulated output voltage by means of
a nano-power high efficiency synchronous buck regulator.
The LTC3588 has an internal full-wave bridge rectifier accessible via PZ1 and PZ2 that rectifies AC inputs such as those from a piezoelectric element. The
rectified output is stored on a capacitor at the VIN pin
and can be used as an energy reservoir for the buck
converter. The bridge is capable of carrying up to
50mA.
When the voltage on VIN crosses the UVLO rising
threshold the buck converter is enabled and charge
is transferred from the input capacitor to the output
capacitor. A wide (~1V) UVLO hysteresis window is
employed with a lower threshold approximately
200mV above the selected regulated output voltage
to prevent short cycling during buck power-up.
When the input capacitor voltage is depleted below
the UVLO falling threshold the buck converter is disabled.
Two internal rails, CAP and VIN2, are generated from
VIN and are used to drive the high side PMOS and
low side NMOS of the buck converter, respectively.
Additionally the VIN2 rail serves as logic high for output voltage select bits D0 and D1. The VIN2 rail is regulated at 4.8V above GND while the CAP rail is regulated at 4.8V below VIN. These are not intended to be
used as external rails. Capacitors should be con-
2
nected to the CAP and VIN2 pins to serve as energy
reservoirs for driving the buck switches.
The buck regulator uses a hysteretic voltage algorithm to control the output through internal feedback
from the VOUT sense pin. The buck converter charges
an output capacitor through an inductor to a value
slightly higher than the regulation point. It does this
by ramping the inductor current up to 250mA
through an internal PMOS switch and then ramping it
down to 0mA through an internal NMOS switch.
When the buck brings the output voltage into regulation the converter enters a low quiescent current
sleep state that monitors the output voltage with a
sleep comparator. During this operating mode load
current is provided by the buck output capacitor.
When the output voltage falls below the regulation
point the buck regulator wakes up and the cycle repeats. This hysteretic method of providing a regulated output reduces losses associated with FET
switching and maintains an output at light loads. The
buck delivers a minimum of 100mA average load
current when it is switching.
A power good comparator produces a logic high referenced to VOUT on the PGOOD pin the first time the
converter reaches the programmed VOUT, signaling
that the output is in regulation. The PGOOD pin will
remain high until VOUT falls to 92% of the desired
regulated voltage.
LTC3588EMSE-1/-2
QUICK START PROCEDURE
Using short twisted pair leads for any power connections, with all loads and power supplies off, refer
to Figure 1 for the proper measurement and equipment setup.
Follow the procedure below:
1. Before connecting PS1 to the DC1459B, PS1
must have its current limit set to 50mA. For
most power supplies with a current limit adjustment feature the procedure to set the current limit is as follows. Turn the voltage and
current adjustment to minimum. Short the
outputs terminals and turn the voltage adjustment to maximum. Adjust the current
limit to 50mA. Turn the voltage adjustment to
minimum. The power supply is now current
limited to 50mA.
2. Initial Jumper, PS and LOAD 1settings:
JP1 = 0
PS1 = OFF
JP2 = 0
LOAD1 = OFF
3. Connect PS1 to the VIN Terminals, then turn
on PS1 and slowly increase voltage to 2.0V
while monitoring the input current. If the current remains less than 5mA, increase PS1 to
17.0V.
4. Set LOAD1 to 100mA. Verify voltage on VOUT
is within the VOUT 1.8V/3.45V range in Table
1. Verify that the output ripple voltage is between 40mV and 90mV. Verify that PGOOD is
high (VOUT). Decrease LOAD1 to 5mA.
5. Decrease PS1 to 0V and move the connection
for PS1 from VIN to PZ1. Slowly increase PS1
voltage to 2.0V while monitoring the input
current. If the current remains less than 5mA,
increase PS1 to 17V. Verify voltage on VOUT
is within the VOUT 1.8V/3.45V range in Table
1.Decrease PS1 to 0V, swap the PZ1 move the
lead connections to PZ2 and repeat the test.
Decrease PS1 to 0V and move the connection
for PS1 from PZ2 to VIN.
6. Set JP1 to 1. Increase PS1 to 17V and set
LOAD1 to 100mA. Verify voltage on VOUT is
within the VOUT 2.5V/4.1V range in Table 1.
Verify that the output ripple voltage is between
40mV to 90mV.
7. Set JP1 to 0 and JP2 to 1. Set LOAD1 to
100mA. Verify voltage on VOUT is within the
VOUT 3.3V/4.5V range in Table 1. Verify that
the output ripple voltage is between 50mV and
90mV.
8. Set JP1 to 1 and JP2 to 1. Set LOAD1 to
100mA. Verify voltage on VOUT is within the
VOUT 3.6V/5.0V range in Table 1. Verify that
the output ripple voltage is between 60mV and
110mV.
9. Decrease LOAD1 to 1mA. Turn off PS1 and
insert a 1K ohm resistor between the positive
lead of the PS1 and the VIN turret. Turn on
PS1 and while monitoring the voltage on VIN,
increase PS1 until the voltage on VIN is 3V below the voltage on PS1. Verify input voltage,
VIN, VSHUNT of 19.0V to 21.0V.
10. Turn off PS1 and LOAD1.
3
LTC3588EMSE-1/-2
Figure 1. Proper Measurement Equipment Setup
4
LTC3588EMSE-1/-2
Figure 2: Schematic diagram
5
LTC3588EMSE-1/-2
Bill of Materials
6
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