DC2148A - Demo Manual

DEMO MANUAL DC2148A
LT8709
Negative Input Synchronous
Multi-Topology DC/DC Controller
Description
Demonstration circuit 2148A features the LT®8709, a
negative input synchronous multi-topology DC/DC controller designed for negative input power supplies where
the highest input supply voltage is ground. Examples
of these circuits include negative buck, negative boost,
negative buck-boost and negative inverting. The DC2148A
is a negative buck-boost with an operating input voltage
range from –4.5V to –38V and an output voltage of –12V,
however this demo circuit can be easily reconfigured for
other negative input topologies. The maximum output current for DC2148A is 5A, the switching frequency is 400kHz
and the maximum efficiency with a –12V input is 91%.
The output voltage is programmed with a single resistor R7 and a –4.22V turn-on threshold is programmed
with resistor divider R3 and R4. Current sense resistor
R1 programs the switch current limit and current sense
resistor R2 programs an output current limit. Filters can
be added to the switch and output current sense resistors
using component placeholders on the PCB. The IMON output voltage is proportional to output current and a 0.1µF
capacitor C17 filters IMON.
This demo circuit uses logic-level 60V NMOS and PMOS
that operate down to a –4.5V input voltage. Diode D1 is
in parallel with the PMOS to improve efficiency. Resistors can be added to the gate drives of both NMOS and
PMOS. There are placeholders so the NMOS and PMOS
can be paralleled.
Ceramic capacitors are used at both the circuit input and
output because of their small size and high ripple current
capability. The input has an aluminum electrolytic capacitor in addition to the ceramic capacitors and there is a
placeholder to add an electrolytic capacitor at the output.
The MODE input is pulled up to INTVCC by 100k resistor
R14 which allows discontinuous conduction mode (DCM)
and pulse-skipping operation. There is a placeholder that
can be used to connect MODE to –VIN instead of INTVCC
for continuous conduction mode (CCM) switching.
The switching frequency is adjustable using resistor R5.
The SYNC input can be used to synchronize the switching frequency. Zero ohm jumper R16 from SYNC to –VIN
must be removed prior to using the SYNC input. Feedback
loop compensation can be optimized using components
R6, C7 and C8.
Capacitor C14 at the SS pin programs soft-start. PG is an
open-collector status flag output and is pulled up to the
INTVCC pin voltage by the 100k resistor R23.
There are placeholders to add level shifting circuitry for
EN/FBIN, SYNC and PG signals. In addition, the demo
circuit is designed to be easily reconfigured to many other
applications, including the example schematics in the data
sheet. The PCB has extensive vias for thermal performance.
Synchronous switching and negative input operation
make the LT8709 attractive for negative input, high-power
voltage regulator circuits. The LT8709EFE is available in a
thermally enhanced 20-lead TSSOP package. The LT8709
data sheet must be read in conjunction with this demo
manual to properly use or modify DC2148A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2148A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
dc2148af
1
DEMO MANUAL DC2148A
Performance Summary
PARAMETER
Specifications are at TA = 25°C
CONDITIONS
MIN
TYP
MAX
–4.5
Minimum Input Voltage, V–VIN
UNITS
V
–38
Maximum Input Voltage, V–VIN
V
Maximum Output Current (See Figure 2), IOUT
–12V > V–VIN > –38V
V–VIN = –4.5V
Input EN/FBIN Turn-On Voltage, V–VIN
R3 = 13.3k, R4 = 10k 1%, VGND,–VIN = Rising
Output Voltage, VOUT
R7 = 130k
Efficiency
V–VIN = –12V, IOUT = 2.5A
91
%
Switching Frequency
R5 = 88.7k
400
kHz
Output Current Limit
R2 = 0.006Ω, 1%
8.3
A
2
5
2.5
A
A
–4.22
–12.5
V
–11.7
V
dc2148af
DEMO MANUAL DC2148A
Quick Start Procedure
To use DC2148A to evaluate the performance of the LT8709,
refer to Figure 1 for the proper measurement equipment
setup, Figure 2 for the maximum output current versus
input voltage and then follow the procedure:
NOTE: Make sure that the voltage applied to –VIN does
exceed –38V. A GND to –VIN voltage that is greater than
38V may cause voltage spikes that occur during switching
to exceed the voltage ratings at the drains of the NMOS
and PMOS.
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 to terminals across
the –VIN or VOUT capacitors. See Figure 3 for proper scope
probe technique.
1.Connect the EN/FBIN terminal to –VIN with a clip-on
lead. Connect the power supply (with power off), load,
and meters as shown in Figure 1.
2.After all connections are made, turn on the input power
and verify that the input voltage is between –4.5V and
–38V.
3.Remove the clip-on lead from EN/FBIN. Verify that the
output voltage is –12V.
NOTE: If the output voltage is low, temporarily disconnect
the load to make sure that it is not set too high.
Once the proper output voltage is established, adjust the
input voltage and load within the operating ranges and
observe the output voltage regulation, ripple voltage, efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup for DC2148A
dc2148af
3
DEMO MANUAL DC2148A
Quick Start Procedure
MAXIMUM OUTPUT CURRENT (A)
6
5
4
3
2
1
0
0
–5
–10 –15 –20 –25 –30 –35 –40
INPUT VOLTAGE (V)
DC2148A F01
Figure 2. Maximum Output Current vs Input Voltage
VOUT
PGND
Figure 3. Proper Scope Probe Technique
4
dc2148af
DEMO MANUAL DC2148A
Quick Start Procedure
100
95
EFFICIENCY (%)
90
85
80
75
70
65
60
V–VIN = –4.5V
V–VIN = –12V
V–VIN = –18V
55
50
0
1
2
3
4
LOAD CURRENT (A)
5
6
DC2148A F04
Figure 4. Efficiency
VOUT
500mV/DIV
100mV/DIV
IOUT
2A/DIV
1µs/DIV
DC2148A F05
Figure 5. Output Voltage Ripple at 5A Output
Current, V–VIN = –12V, VOUT = –12V
200µs/DIV
DC2148A F06
Figure 6. Output Voltage Load Transient Response,
V–VIN = –12V, VOUT = –12V, IOUT = 2.5A to 5A to 2.5A
dc2148af
5
DEMO MANUAL DC2148A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
5
C1, C2, C3, C4, C18
Cap., X5R 10µF 50V 10% 1210
MURATA GRM32ER61H106KA12L
2
5
C5, C6, C11, C12, C13
Cap., X5R 22µF 16V 20% 1210
TDK C3225X5R1C226M
3
1
C7
Cap., X7R 4.7nF 25V 10% 0603
AVX 06033C472KAT2A
4
1
C8
Cap., NPO 47pF 25V 10% 0603
AVX 06033A470KAT2A
5
2
C9, C16
Cap., X7R 2.2µF 100V 10% 1210
Murata GRM32ER72A225KA35L
6
2
C10, C15
Cap., X7R 2.2µF 16V 20% 0805
Taiyo Yuden EMK212BJ225MG
7
1
C14
Cap., X5R 0.22µF 50V 20% 0603
TDK C1608X5R1H224M
8
1
C17
Cap., X7R 0.1µF 25V 10% 0603
AVX 06033C104KAT2A
9
1
D1
Diode Schottky, 60V/3Amp SOD-128
Philips(NXP) PMEG6030EP
10
1
L1
Inductor, 3.5µH ± 20%
Würth Electronik 74485540350
11
1
MN1
MOSFET, Single N-Channel 22A/60V Power 56
Fairchild Semi. FDMS86520L
12
1
MP1
MOSFET, Single P-Channel 60V DPAK
Vishay SUD19P06-60-E3
13
1
R1
Res., 0.002 2W 1% 2512
Vishay WSL-2512-2L000-F-EA
14
1
R2
Res., 0.006 1W 1% 2512
Vishay WSL-2512-6L000-F-EA
15
1
R3
Res., Chip 13.3k 0.06W 1% 0603
Vishay CRCW060313K3FKEA
16
1
R4
Res., Chip 10.0k 0.06W 1% 0603
Vishay CRCW060310K0FKEA
17
1
R5
Res., Chip 88.7k 0.06W 1% 0603
Vishay CRCW060388K7FKEA
18
1
R6
Res., Chip 10k 0.06W 5% 0603
Vishay CRCW060310K0JNEA
19
1
R7
Res., Chip 130k 0.06W 1% 0603
Vishay CRCW0603130KFKEA
20
1
U1
I.C., Volt. Reg. TSSOP20-FE/CB
Linear Tech. Corp. LT8709EFE
Additional Demo Board Circuit Components
1
0
C20, C23, C24, C25, C30,
C31, C32 (Opt)
Cap., 0603
2
1
C21
Cap., Alum 220µF 50V 20% 10mm Dia. SMD
3
0
C19, C22, C27, C28, C29,
C35, C36, C37 (Opt)
Cap., 1210
4
0
C26 (Opt)
Cap., 8mm Dia. SMD
5
0
C33, C34, C39 (Opt)
Cap., 0805
Sun Elect. 50CE220AX
6
0
C38 (Opt)
Cap., X7R 0.1µF 100V 10% 1206
AVX 12061C104KAT2A
7
0
D2, D3 (Opt)
Schottky Barrier 100V SOD323
NXP Semi. BAT46WJ
8
0
D4 (Opt)
Schottky Diode PowerDi5
9
0
D5 (Opt)
Diode, SOD-323
10
0
MN2 (Opt)
MOSFET, Single N-Channel 60V PowerPAK SO8
11
0
MP2 (Opt)
MOSFET, Single P-Channel PowerPAK SO8
12
0
Q1 (Opt)
Trans., PNP SOT23
Zetex FMMT593
13
0
Q2 (Opt)
XSTR, NPN SOT-23
Diode Inc. MMBT2222A
14
0
R8, R9, R10, R11, R12,
R13, R15, R17, R18, R21,
R22, R25, R26, R31, R32,
R33, R34, R37, R38, R39,
R45 (Opt)
Res., 0603
6
dc2148af
DEMO MANUAL DC2148A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
15
2
R14, R23
Res., Chip 100k 0.06W 5% 0603
Vishay CRCW0603100KJNEA
16
2
R16, R20
Res/Jumper, Chip 0Ω 0.25W 5A 0603
Vishay CRCW06030000Z0EA
17
1
R19
Res/Jumper, Chip 0Ω 1.5W 16A 2512
Vishay CRCW25120000ZOEA
18
0
R24, R27, R28, R29, R36
(Opt)
Res., 2512
19
0
R30, R35, R40 (Opt)
Res., Chip 1k 0.06W 5% 0603
Vishay CRCW06031K00JNEA
20
0
R41 (Opt)
Res., Chip 100k 0.06W 5% 0603
Vishay CRCW0603100KJNEA
21
0
R42, R43, R44 (Opt)
Res., Chip 20k 0.06W 5% 0603
Vishay CRCW060320K0JNEA
Hardware: For Demo Board Only
1
11
E1, E2, E3, E4, E5, E6, E7,
E8, E9, E10, E11
Turret, Testpoint
Mill Max 2501-2-00-80-00-00-07-0
2
4
J1, J2, J3, J4
Connector, Banana Jack
Keystone 575-4
3
4
MH1-MH4
STAND-OFF, NYLON 0.50" Tall (SNAP ON)
Keystone 8833
dc2148af
7
‐4.5V TO ‐38V
+
C18
10µF
50V
1210
C1
10µF
50V
1210
C2
10µF
50V
1210
SYNC
MODE
EN/FBIN
‐VIN
‐4.5V TO ‐38V
E6
E5
E4
E3
SYNC
EN/FBIN
NOTE: UNLESS
OTHERWISE SPECIFIED
1) ALL RESISTRORS 5%,
0603
2) ALL CAPACITORS 0603
E2
C21
220µF
50V
10mm Dia. SMD
J2
‐VIN
J1
C3
10µF
50V
1210
C4
10µF
50V
1210
(Opt)
(Opt)
C24
C23
R8
(Opt)
‐VIN
(Opt)
C25
4
GND
R16
0 Ohm
(Opt)
R15
100k
R14
10.0k
1%
C10
2.2uF
16V
0805
INTVCC
2.2µF
100V R3
1210 13.3k
1%
R4
C9
R10
(Opt)
MN1
FDMS86520L
L1A
3.5µH
74485540350
Wurth Electronik
L1A‐1
1
INTVCC
0.002
1%
2W
2512 R9
(Opt)
R1
GND
12
19
17
16
13
INTVCC
SYNC
MODE
EN/FBIN
GND
CSP
BG
22uF 16V
1210
22uF 16V
1210
C6
(Opt)
1210
C5
(Opt)
1210
C28
C22
D1
PMEG6030EP
MP1‐D
MP1‐S
R2
0.006
1%
1W
2512
C14
0.22µF
R5
88.7k
1%
400kHz
U1
LT8709EFE
6
PGND
14
CSN
SS
3
11
BG
RT
18
‐VIN
20
15
CSP
10
TG
7
ISP
21
R11
R13
(Opt)
BIAS
ISN
ISP
TG
IMON
VC
FBY
PG
PG
4
5
2
C17
0.1µF
IMON
INTVEE
9
1
BIAS
8
(Opt)
R18
(Opt)
R17
MP1
SUD19P06‐60‐E3
(Opt)
R12
(Opt)
INTVEE
ISN
8
‐VIN
E1
C7
4.7nF
R6
10k
C15
2.2uF
16V
0805
C8
47pF
R20
0 Ohm
R45
(Opt)
C16
2.2µF
100V
1210
2512
R19
0 Ohm
L1B‐3
(Opt)
130k
1%
C20
R7
R23
100k
INTVCC
L1B
2
3.5µH
74485540350
Wurth Electronik
3
C13
22uF
16V
1210
C11
22uF
16V
1210
C12
22uF
16V
1210
* SEE FIGURE 2 FOR
IOUT MAX. VS. -VIN
C19
(Opt)
1210
TG
INTVCC
SYNC
*
E8
PG
E11
‐VIN
E10
IMON
E9
VOUT ‐12V
‐4.5V TO ‐38V
EN/FBIN
PG
BIAS
‐VIN
CSP
MP1‐S
BG
INTVEE
ISN
ISP
L1B‐3
PGND
C26
8mm Dia . SMD
(Opt)
VOUT
J4
MP1‐D
L1A‐1
+
J3
E7
DEMO MANUAL DC2148A
Schematic Diagram
dc2148af
‐VIN
INTVCC
‐VIN
SYNC
EN/FBIN
PG
BIAS
CSP
MP1‐S
BG
INTVEE
ISN
ISP
L1B‐3
TG
MP1‐D
L1A‐1
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.
C39
VOUT
(Opt)
2512
R38
(Opt)
R37
(Opt)
(Opt)
0805
BIAS
ISP
R28
INTVEE
ISN
(Opt)
R21
R32
(Opt)
R31
(Opt)
(Opt)
2512
ISP
(Opt)
R22
‐VIN
C31
(Opt)
ISP
D4
2
1
(Opt)
C30
ISN
C32
(Opt)
L1B‐3
MP2
(Opt)
PowerPAK SO8
C34
(Opt)
0805
TG
VOUT
L1A‐1
(Opt)
PowerDi5
3
R33
(Opt)
BIAS
R26
(Opt)
R34
(Opt)
ISN
INTVCC
D5
(Opt)
SOD‐323
(Opt)
0805
C33
(Opt)
2512
R27
(Opt)
1210
(Opt)
2512
C36
(Opt)
1210
R24
INTVEE
ISN
R29
R25
(Opt)
ISP
MP1‐S
MP1‐D
(Opt)
1210
C27
C35
R42
20k
(Opt)
VOUT
PG
C37
(Opt)
1210
R30
1k
(Opt)
OPTIONAL LEVEL
SHIFTING
CIRCUITRY
D3
BAT46WJ
(Opt)
SOD323
C29
(Opt)
1210
E12
V_EXT
E13
PGND
(Opt)
2512
R36
R43
20k
(Opt)
Q2
MMBT2222A
(Opt)
SOT‐23
R35
1k
(Opt)
‐VIN
CSP
‐VIN
EN/FBIN
R41
100k
(Opt)
SYNC
R44
20k
(Opt)
Q1
FMMT593
(Opt)
SOT23
R40
1k
(Opt)
‐VIN
D2
BAT46WJ
(Opt)
SOD323
L1A‐1
BG
C38
0.1uF
100V
(Opt)
1206
R39
(Opt)
MN2
(Opt)
PowerPAK SO8
DEMO MANUAL DC2148A
Schematic Diagram
dc2148af
9
DEMO MANUAL DC2148A
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
10 Linear Technology Corporation
dc2148af
LT 0315 • PRINTED IN USA
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(408) 432-1900
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