DEMO MANUAL DC1750A
LT8611
42V, 2.5A Micropower Synchronous
Step-Down Regulator with Current Sense
DESCRIPTION
Demonstration circuit 1750A is a 42V, 2.5A micropower
synchronous step-down regulator with current sense
featuring the LT
®
8611. The LT8611 is a compact, high ef-
ficiency, high speed synchronous monolithic step-down
switching regulator that consumes only 2.5μA of quiescent
current when output is regulated at 3.3V. Top and bottom
power switches, compensation components and other
necessary circuits are inside of the LT8611 to minimize
external components and simplify design.
The demonstration circuit has output current limit set at
2.5A by default. The current limit can be moved to the input
side for application where input supply current is limited,
such as energy harvesting application. ICTRL and IMON on
the board set and monitor the regulated current respectively.
The SYNC pin on the demo board is grounded by default
for low ripple Burst Mode
®
operation. To synchronize to an
external clock, move JP1 to SYNC and apply the external
clock to the SYNC turret. Once JP1 is on SYNC position,
a DC voltage of higher than 2V or INTV
CC
can be applied
to the SYNC turret for pulse skipping operation. Figure 1
shows the efficiency of the circuit at 12V input.
The demo board has an EMI filter installed. The EMI
performance of the board is shown on Figure 2. Figure 3
shows the EMI performance of the board running at 1MHz
switching frequency. The limit in Figure 2 and Figure 3 is
EN55022 Class B. Both figures show the circuit passes
the test with a wide margin. To use the EMI filter, the input
should be tied to VEMI, not VIN.
The LT8611 datasheet gives a complete description of the
part, operation and application information. The data sheet
must be read in conjunction with this quick start guide for
demo circuit 1750A.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
12V
IN
to 3.3V
OUT
Efficiency
100
95
EFFICIENCY (%)
90
85
80
0
0.5
1
1.5
LOAD CURRENT (A)
2
2.5
1750 F01
Figure 1. LT8611 Efficiency from 12V to 3.3V (R5 = 0)
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DEMO MANUAL DC1750A
QUICK START PROCEDURE
Demonstration circuit 1750A is easy to set up to evalu-
ate the performance of the LT8611. Refer to Figure 4 and
Figure 5 for proper measurement equipment setup and
follow the procedure below:
1. With power off, connect the input power supply to VIN
and GND.
2. With power off, connect the load VOUT and GND.
3. Check JP1 setting
4. Turn on the power at the input.
5. Carefully evaluate other design parameters as needed.
Figure 4. Proper Measurement Equipment Setup
Figure 5. Measure Output Ripple
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DEMO MANUAL DC1750A
PARTS LIST
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
5
6
7
8
9
1
2
3
4
QTY
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
0
1
1
1
0
2
9
1
1
4
REFERENCE
C2
C4
C6
C7
C8
C9
L1
R5
R8
R9
R10, R12
R11
U1
C1
C10
C3
C5
FB1
L2
R1
R2, R3, R4
R6, R7
E1-E7, E9, E10
JP1
XJP1
MH1-MH4
PART DESCRIPTION
CAP CER 4.7μF 50V 1206
,
CAP CER 0.22μF 16V 0603
,
CAP CER 47μF 10V 1210
,
CAP CER 1.0μF 25V 0603
,
CAP CER 0.1μF 0402
,
CAP CER 4.7pF 25V 0402
,
IND, 4.7μH
RES, 0.02Ω 1% 1206
RES, 60.4k 1% 0402
RES, 49.9k 1% 0402
RES, 1M 1% 0402
RES, 412k 1% 0402
IC, LT8611EUDD QFN24EUDD
CAP ALUM 22μF 63V
,
CAP CER 4.7μF 50V 1206
,
CAP CER 4.7μF 50V 1206
,
CAP OPT 0402
,
FERRITE BEAD 0805
IND, 4.7μH
RES, 0Ω 1206
RES, OPT 0402
RES, 0Ω 0402
TESTPOINT TURRET 0.094"
HEADER 1X3 0.079"
SHUNT, 0.079" CENTER
STAND-OFF NYLON 0.50" TALL
,
MANUFACTURER/PART NUMBER
TAIYO YUDEN UMK316BJ475KL
TAIYO YUDEN EMK107BJ224KA-T
MURATA, GRM32ER71A476K
MURATA GRM188R71E105K
AVX, 0402YD104KAT2A
AVX, 04023A4R7CAT
COILTRONICS HCM0703-4R7-R
VISHAY, WSL1206R0200FEA
VISHAY, CRCW040260K4FKED
VISHAY, CRCW040249K9FKED
VISHAY, CRCW04021M00FKED
VISHAY, CRCW0402412KFKED
.
LINEAR TECH.CORP LT8611EUDD
SUNCON 63CE22BS
TAIYO YUDEN UMK316BJ475KL
MURATA, GRM31CR71H475K
OPT
TDK, MPZ2012S221A
VISHAY, IHLP2020BZ-ER4R7M01
AAC CJ18-000M
OPT
AAC, CJ05-000M
MILL-MAX-2501-2
SAMTEC, TMM-103-02-L-S
SAMTEC, 2SN-BK-G
KEYSTONE, 8833 (SNAP ON)
Required Circuit Components
Additional Demo Board Circuit Components
Hardware/Components (For Demo Board Only)
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