DEMO MANUAL DC1768A
DESCRIPTION
LTC3626EUDC
20V, 2.5A Synchronous Monolithic
Step-Down Regulator with Current
and Temperature Monitoring
Demonstration circuit 1768A is a step-down converter,
using the LTC3626 monolithic synchronous buck regulator,
which has current and temperature monitoring capabilities.
The 1768A has an input voltage range of 3.6V to 20V, and
is capable of delivering up to 2.5A of output current. The
output voltage of the 1768A can be set as low as 0.6V, the
reference voltage of the LTC3626. At light load currents, the
1768A is capable of operating in Burst Mode™, which makes
for greater efficiency, and during shutdown, it consumes
less than 2μA of quiescent current. In continuous mode
operation, the 1768A is a high efficiency circuit over 90%.
The 1768A can also track another voltage with the LTC3626
track function. Because of the current and temperature
monitoring and limiting capabilities of the LTC3626, the
1768A input or output current, as well as its maximum
temperature can be limited or clamped. The 1768A uses
low profile surface mount components, due to the high
switching frequency capability of the LTC3626, which is
programmable up to 3MHz. All these features make the
1768A an ideal circuit for use in industrial applications.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PERFORMANCE SUMMARY
PARAMETER
CONDITIONS
VALUE
Input Voltage Range
3.6V –20V
Output Voltage Range
0.6V-6V
Run/Shutdown
GND = Shutdown
VIN = Run
Output Voltage Regulation
VIN = 3.6V to 20V, IOUT = 0A to 2.5A
1.2V ±2% Typ. (1.176V – 1.224V)
VIN = 3.6V to 20V, IOUT = 0A to 2.5A
1.8V ±2% Typ. (1.764V – 1.836V)
VIN = 4V to 20V, IOUT = 0A to 2.5A
3.3V ±2% Typ. (3.234V – 3.366V)
Typical Output
Ripple Voltage
VIN = 12V, VOUT = 1.8V
IOUT = 2.5A (20MHz BW)
< 20mVP-P
Burst Mode-to-Continuous Mode
Transition Current Values
VIN = 12V, VOUT = 1.2V
IOUT < 680mA
VIN = 12V, VOUT = 1.8V
IOUT < 880mA
VIN = 12V, VOUT = 3.3V
IOUT < 1.2A
Mode Pin = INTVCC
Burst Mode
Mode = GND
FCM (Forced Continuous Mode)
Mode
Nominal Switching Frequency
Mode = Floating
Synchronized or Burst Mode
RT = 324k
1MHz ±20%
RT connected to INTVCC
2MHz ±30%
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1
DEMO MANUAL DC1768A
QUICK START PROCEDURE
Demonstration Circuit 1768A is easy to set up to evaluate
the performance of the LTC3626. For proper measurement
equipment configuration, set up the circuit according to
the diagram in Figure 1. Before proceeding to test, check
that the shunts are inserted into the default locations: 1.2V
position of the output voltage header JP1, the SS position of the soft-start/track header JP5, the FCM (Forced
Continuous Mode) position of the MODE header JP6, the
ON position of RUN header JP7, the 1MHz position of the
frequency header JP8, the EXT position of the ITH header
JP9, the SET/OFF position of the temperature set header
JP10, the OFF position of the temp. monitoring header
JP11, the OFF position of the output current monitoring
header JP12, and the OFF position of the input current
monitoring header JP13.
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 VIN or VOUT
and GND terminals. See Figure 2 for proper scope probe
measurement technique.
With the 1768A set up according to the proper measurement configuration and equipment in Figure 1, apply 6.3V
at VIN (Do not hot-plug VIN or increase VIN over the rated
maximum supply voltage of 20V, or the part may be damaged.). Measure VOUT; it should read 1.2V (If desired, the
quiescent current of the circuit can be monitored now by
swapping the shunt in header JP7 into the OFF position.).
The output voltage should be regulating. Measure VOUT it
should measure 1.2V ±1% (1.188V to 1.212V).
Vary the input voltage from 3.6V to 20V and adjust the
load current from 0 to 2.5A. VOUT should regulate around
1.2V ±2% (1.176V to 1.224V). Measure the output ripple
voltage; it should measure less than 20mVAC. Set the input
voltage to 12V and the output current to any current less
than 1.25A. Observe the discontinuous mode of operation
at the switch node, and measure the output ripple voltage.
It should measure less than 50mV. Change the shunt
position on the MODE header from BM to FCM (Forced
Continuous Mode) and observe the voltage waveform at
the switch pins (the other side of the inductor from the
output). Verify the switching frequency is between 850kHz
and 1.2MHz (T = 1.17μs and 833ns), and that the switch
node waveform is rectangular in shape.
Insert the JP7 shunt into the OFF position and move the
shunt in the 1.2V output JP1 header into any of the two
remaining output voltage option headers: 1.8V (JP2) or
3.3V (JP3). Just as in the 1.2V VOUT test, the output voltage should read VOUT ±1% tolerance under static line and
load conditions and ±1% tolerance under dynamic line and
load conditions ±2% total). Also, the circuit operation in
discontinuous mode will be the same.
Monitor the input and output currents, and the die temperature, by changing the shunts on headers JP13, JP12,
and JP11, respectively. The currents and temperature can
even be limited using headers JP13, JP12, and JP10 – the
TSET header, and adjusting the values of resistors R12,
R13, and R14 (Consult the Input/Output Current and OnDie Temperature Monitor and Limit section of the LTC3626
datasheets for more details.).
When finished, turn off the circuit by inserting the shunt
in header JP7 into the OFF position.
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DEMO MANUAL DC1768A
QUICK START PROCEDURE
Table 1. Jumper Description
JUMPER
FUNCTION
RANGE/SETTING (DEFAULT)
JP1
Output Voltage Setting.
1.2V
JP5
Soft-Start (TRACK or SS)
TRACK – (SS)
JP6
MODE/SYNC: Forced Continuous Mode (FCM), Burst Mode, or SYNC
(FCM) – BM – SYNC
JP7
RUN
(ON) – OFF
JP8
Frequency (FREQ)
(1MHz) – 2MHz
JP9
ITH: External Comp. (EXT) or Internal (INTVCC) Comp. (INT)
(EXT) – INT
JP10
Temperature Setting (TSET): Externally Set (EXT SET) or Internally Set (INTVCC) or Off (SET/OFF)
EXT SET – (SET/OFF)
JP11
Temperature Monitoring (TMON)
ON – (OFF)
JP12
Output Current Monitoring (IOUT)
ON – (OFF)
JP13
Input Current Monitoring (IIN)
ON – (OFF)
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DEMO MANUAL DC1768A
QUICK START PROCEDURE
IIN
+
–
IOUT
+
+
+
VS
–
–
VIN
+
–
VOUT
–
+
LOAD
–
Figure 1. Proper Equipment Measurement Set-Up
GND
VIN
Figure 2. Measuring Input or Output Ripple
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DEMO MANUAL DC1768A
QUICK START PROCEDURE
Normal Switching Frequency and Output Ripple Voltage Waveforms
Figure 3. Switch Node Voltage, Output Ripple Voltage & Inductor Ripple Current Waveforms
VIN = 12V, VOUT = 3.3V, IOUT = 2.5A, fSW = 1MHz Trace 1: Switch Voltage (10V/DIV)
Trace 2: Output Ripple Voltage (20mV/DIV AC) Trace 4: Inductor Ripple Current (2A/DIV)
Load Step Response Waveforms
Figure 4. Load Step Response VIN = 12V. VOUT = 1.2V, 2.5A Load Step (0A-2.5A)
Forced Continuous Mode, fSW = 1MHz. Trace 2: Output Voltage (20mV/DIV AC)
Trace 4: Output Current (1A/DIV)
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5
DEMO MANUAL DC1768A
QUICK START PROCEDURE
Load Step Response Waveforms
Figure 5. Load Step Response VIN = 12V, VOUT = 1.8V, 2.5A Load Step (0A-2.5A)
Forced Continuous Mode fSW = 1MHz Trace 2: Output Voltage (50mV/DIV AC)
Trace 4: Output Current (1A/DIV)
Load Step Response Waveforms
Figure 6. Load Step Response VIN = 12V, VOUT = 3.3V, 2.5A Load Step (0A-2.5A)
Forced Continuous Mode fSW = 1MHz Trace 2: Output Voltage (50mV/DIV AC)
Trace 4: Output Current (1A/DIV)
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6
DEMO MANUAL DC1768A
QUICK START PROCEDURE
Figure 7. Input and Output Current Monitoring VIN = 12V, IIN = 620mA, VOUT = 3.3V, IOUT = 2A, fSW = 1MHz
Trace 1: IOUTMON Voltage (0.5V/DIV) Trace 2: IINMON Voltage (0.1V/DIV) Trace 3: IOUT Current (2A/DIV)
Trace 4: IIN Current (500mA/DIV)
With a Current Sense Resistor of 4.02k Connected to Both The Input and Output Current Monitors, Their Voltages Equate to:
VIOUTMON = 2A/16000 × 4.02k = 0.503V
VINMON = 620mA/16000 × 4.02k = 0.156V
95
Vo = 3.3V
80
Vo = 1.8V
Vo = 1.2V
Efficiency (%)
65
50
35
20
1.00E-03
1.00E-02
1.00E-01
Load Current (A)
1.00E+00
1.00E+01
Figure 8. Efficiency Graph VIN = 12V, Burst Mode,
fSW = 1MHz L:1 μH Vishay IHLP-2020BZ-ER-1R0-MO1
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DEMO MANUAL DC1768A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Cap., NP0, 220pF, 25V, 10%, 0402
AVX, 04023A221KAT2A
Required Circuit Components
1
1
CITH
2
1
C1
Cap., X5R, 2.2μF, 16V, 20%, 0603
TDK, C1608X5R1C225M
3
2
C3, C6
Cap., X7R, 22μF, 25V, 20%, 1210
MURATA, GRM32ER71E226M
4
1
C4
Cap., X5R, 47μF, 6.3V, 20%, 1206
Taiyo Yuden, JMK316BJ476ML-T
5
1
C5
Cap., NP0, 22pF, 50V, 10% 0402
AVX, 04025A220KAT
6
1
C8
Cap., X7R, 0.1μF, 25V, 10% 0603
TDK, C1608X7R1E104K
7
1
C11
Cap., X5R, 1μF, 6.3V, 10% 0402
AVX, 04026D105KAT2A
8
1
L1
Inductor, 1.0μH IHLP-2020BZ-01
Vishay IHLP-2020BZER1R0M01
9
1
RITH
Res., Chip, 13k, 0.06W, 5% 0402
VISHAY, CRCW040213K0JNED
10
2
R3, R4
Res., Chip, 115k, 0.06W, 1% 0402
VISHAY, CRCW0402115KFKED
11
1
U1
IC. LTC3626EUDC, 3 × 4mm, 20 QFN
LINEAR TECH., LTC3626EUDC#PBF
Additional Demo Board Circuit Components
12
0
CC(OPT)
Cap., 0402
13
1
C2
Cap., Tant. 3.3μF, 35V, 20%, 6032
14
0
C7, C10(OPT)
Cap., 1206
15
1
C9
Cap., X7R, 2200pF, 25V, 20%, 0402
AVX, 04023C225MAT
16
2
C12, C13
Cap., X5R, 1μF, 25V, 10%, 0603
TDK, C1608X5R1E105K
17
0
C14(OPT)
Cap., 1812
18
1
C15
Cap., X5R, 0.33μF, 25V, 20%, 0603
19
0
D1(OPT)
Schottky Diode, SOD-323
AVX, TAJW335M035R
AVX, 06033D334MAT
20
2
R10, RON
Res., Chip, 0Ω, 0.06W, 0402
VISHAY, CRCW04020000Z0ED
21
1
R1
Res., Chip, 100k, 0.06W, 5%, 0402
VISHAY, CRCW0402100KFKED
22
1
R2
Res., Chip, 324k, 0.06W, 1%, 0402
NIC, NRC04F3243TRF
23
1
R5
Res., Chip, 57.6k, 0.06W, 1%, 0402
VISHAY, CRCW040257K6FKED
24
1
R6
Res., Chip, 25.5k, 0.06W, 1%, 0402
VISHAY, CRCW040225K5FKED
25
0
R7, R9, R14(OPT)
Res., 0402
26
2
R8, R11
Res., Chip, 1M, 0.06W, 5%, 0402
VISHAY, CRCW04021M00JNED
27
2
R12, R13
Res., Chip, 4.02k, 0.06W, 1%, 0402
VISHAY, CRCW04024K02FKED
28
1
R17
Res., Chip,10Ω, 0.06W, 5%, 0402
VISHAY, CRCW040210R0JNED
Hardware: For Demo Board Only
29
13
E1-E13
Turret,Testpoint
Mill Max2501-2-00-80-00-00-07-0
30
4
JP1, JP2, JP3, JP4
2 PIN 0.079 SINGLE ROW HEADER
SAMTEC, TMM102-02-L-S
31
1
JP5
2X2, 0.079 DOUBLE ROW HEADER
SAMTEC, TMM102-02-L-D
32
1
JP6
2X3, 0.079 DOUBLE ROW HEADER
SAMTEC, TMM103-02-L-D
33
7
JP7-JP13
3 PIN 0.079 SINGLE ROW HEADER
SAMTEC, TMM103-02-L-S
34
10
XJP1, XJP5-XJPP13
SHUNT, .079" CENTER
SAMTEC, 2SN-BK-G
35
4
MH1-MH4
STAND-OFF, NYLON 0.25"
KEYSTONE, 8831(SNAP ON)
dc1768af
8
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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SCHEMATIC DIAGRAM
dc1768af
9
DEMO MANUAL DC1768A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1768af
10 Linear Technology Corporation
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