International Rectifier
IRDC2085S-DF DEMO BOARD EVALUATION PROCEDURE
International Rectifier • 233 Kansas Street, El Segundo, CA 90245 USA
Overview
This document describes how to connect and evaluate the supplied IRDC2085S-DF demo board. The demo board
incorporates a new DC Bus Converter chipset in a fixed-frequency, open-loop isolated half-bridge DC-DC
converter with 6:1 input to output voltage conversion ratio. The chipset consists of a primary side IC (IR2085S),
two 80V primary side FETs (IRF7493), two 30V secondary side FETs (IRF6618), a primary side biasing FET
(IRF7380) and a secondary side gate clamp FET (IRF9956). The front side of the demo board is shown in Fig. 1.
-Vin
+ Vin
- Vout
+ Vout
-Vin
+ Vin
- Vout
+ Vout
Fig. 1 Front side of the DC Bus Converter demo board with IR2085S ChipSet with marked input and output pins.
This version of the Demo Board employs DirectFET Power MOSFETs for secondary synchronous rectification *
IRDC2085S-DF Quick Evaluation Procedure
To evaluate the operation and performance of the IRDC2085S-DF demo board, connect a power supply to its
input terminals, and a power load to its output terminals. Input and output terminals are marked in Fig. 1. To
duplicate the performance data reported on page two, approximately 400 LFM of airflow is needed across the
module.
The circuit will start to operate as soon as the primary Vcc reaches about 9V – typically at 12Vin. At this low
input voltage, the output voltage will be only about 2V, and the secondary Vcc will be insufficient to fully
enhance the secondary side synchronous rectifier MOSFETs. To avoid excessive body diode conduction losses,
output current during slow input voltage ramp-up should be set at less than 2A.
IRDC2085S-DF Demo Board Description and circuit capability
The circuit is designed to deliver continuous 20A output current in 36V – 60V input voltage range, with 400 LFM
of airflow. Output voltage for this input voltage range will vary from 6V to 10V, and the total available output
power from the module will range from around 120W at 36V to up to 200W at 60V input.
The circuit design is optimized in order to demonstrate true performance of the IR2085S control IC, IRF7493
primary FETs and IRF6618 secondary DirectFETs. Therefore, no test pins are available on the board. To probe
the circuit waveforms use an oscilloscope probe with minimal length for the ground pin and connect directly to
the pins of the IC / MOSFET device.
To measure circuit efficiency, voltage and current at the input and output of the demo board need to be accurately
measured. Use of calibrated shunts for input and output current measurements is strongly recommended, as is use
of a thermal camera for thermal performance evaluation
*
IRDC2085S
-
DF 150W DC Bus Demo Board
International Rectifier
A complete schematic of the demo board is shown in Fig. 2. Typical efficiency and a thermal image for 150W
output power at 48Vin are shown in Fig. 3. Inputs and outputs of two or more modules can be connected in
parallel to provide required output power higher than 150W. Due to natural output voltage droop associated with
open-loop operation, no additional circuitry is required for relatively accurate current sharing (in the range of +/-
10%).
36~60Vinput C1
3.3u
Rb9
39k
Vcc
C7
22u
Db3
NM4
IRF6618 or IRF7832
NM3
IRF6618 or IRF7832
NM1
IRF7493
NM2
IRF7493
C8
22u
Rb2
200
C2
3.3u
NM5
IRF9956
T
C3
1u
Vcc
CS
OSC
GND
LO VCC
VB
VS
HO
IC1
IR2085S
R
56k
D
L
Cb2
.1u
Db2
9V
C4
1u
C5
1u
C6
47
Rg2
100k
Rg3
10k
Rg4
10k
Vcc
36~60Vinput
Cb1
.1u
Rb10
39k
Rb1
200
Db4
NM6
IRF7380
Db1 15V
Db5 3V
D4
Remote Shutdown
6~10Vout
Fig. 2 Complete schematic of IRDC2085S-DF Demo Board
Fig. 3 Efficiency and Thermal image at 48Vin, 150W out max, @ 400LFM
*IR2085S demo board has (2) versions:
- IRDC2085S-DF (uses IRF6618 DirectFET MOSFETs for secondary synchronous rectifiers NM3 & NM4)
- IRDC2085S-S (uses IRF7832 SO8 MOSFET for secondary synchronous rectifiers NM3 & NM4)
IRF7493 Primary Side and IRF6618 Secondary
94.5
95
95.5
96
96.5
97
5.0 7.5 10.0 12.5 15.0 17.5 20.0
Output Load Current, Io [A]
ElectricaL Efficiency [%]
IRF6618
72
64 71 64
62 68
International Rectifier
IRDC2085S-DF Demo Board PCB Layout (Total of 8 layers)
Top Layer Bottom Layer
Layer #1 Layer #2
Layer #3 Layer #4
Layer #5 Layer #6
Note : The above Gerber file is available upon request
International Rectifier
IRDC2085S-DF DC Bus Converter Demo Board BOM List
Item No Ref. Designator Description Part Number Value Package Vendor
1 IC1 Controller IC IR2085S 100V, +/- 1.0A SO8 IR
2 NM1, NM2 Single N-Channel Power MOSFET IRF7493 80VN, 15mOhm SO8 IR
3 NM3, NM4 Single N-Channel Power MOSFET IRF6618 30VN, 2.2mOhm DirectFET IR
4 NM5 Dual N-Channel Power MOSFET IRF9956 30VN, 100mOhm SO8 IR
5 NM6 Dual N-Channel Power MOSFET IRF7380 80VN, 73mOhm SO8 IR
6 Db4 Dual Rectifier Diode BAT54S 30V SOT23 IR
7 D, Db3 Rectifier Diode BAV16WDICT-ND 75V SOD123 Digi-key
8 Db1, Db6 Zener Diode BZT52C15SDICT-ND 15V SOD323 Digi-key
9 Db2 Zener Diode BZT52C9V1SDICT-ND 9V SOD323 Digi-key
10 Db5 Zener Diode BZT52V3V0SDICT-ND 3V SOD323 Digi-key
11 C1, C2 Ceramic cap THCR50E1H335ZT 3.3u, 50V 1812 Digi-key
12 C3 Ceramic cap ECJ5YB2A105M 1u, 100V 1812 Panasonic
13 C7, C8 Ceramic cap GRM43E61C226KE01B 22u, 16V 1210 Digi-key
14 CB1,CB2 Ceramic cap PCC1840CT-ND 0.1u, 25V 805 Digi-key
15 C4,C5 Ceramic cap PCC2224CT-ND 1u, 16V 805 Digi-key
16 C6 Ceramic cap PCC1470ACVCT-ND 47pf 603 Digi-key
17 Rg3, Rg4 Resistor P10KGCT 10K 603 Digi-key
18 Rb9, Rb10 Resistor P39KACT 39K 805 Digi-key
19 R Resistor P51KGCT 51K 603 Digi-key
20 Rg2 Resistor P100KGCT 100K 603 Digi-key
21 Rb1, Rb2 Resistor P200ECT 200 1206 Digi-key
22 Tr_a, Tr_ PQ Transformer Core, grinded PQ20/16-3F3
Window width =
2.4mm grinded Feroxube
23 2.4 mil Gap PQ core center gaped(cut to fit) material 200FN919 Kapton Polyimide Film Dupont
24 Lo_a Inductor Core, non-gaped half E14/3.5/5-3F3 Feroxube
25 Lo_a Inductor Core, gapped half E14/3.5/5-3F3-A160-E Feroxube
26 PCB
PCB (8 layers: 3 Oz Cu top & bottom layers,
4 Oz Cu center layers, 2.125"x0.8125")
27 Tab For input & output connection 3125-2-00-01-00-00-08-0 Mill-Max
28 Connector Banana Jack, Insulated Nylon, Red & Black J151-ND Digi-key
