MIC3809 Evaluation Board

MIC3809 Evaluation Board
Push-Pull Evaluation Board
General Description
Specifications
The MIC3808 and MIC3809 are part of a family of
complimentary gate drive Push-Pull controllers. The
parts can be used to control any dual-ended
switching converter topology such as Push-Pull,
Half-Bridge or Full-Bridge. The MIC3808 has a
12.5V turn-on threshold while the MIC3809 has a
lower turn-on threshold of 4.3V.
This evaluation board provides a platform for
evaluating the MIC3809 power supply controller IC
in a Push-Pull converter topology. The evaluation
board schematic is shown in Figure 1. Please refer
to the MIC3808/9 data sheet for a detailed
explanation of the control IC.
Control IC..................................................... MIC3809
Power Supply Topology.............................. Push-Pull
Recommended Operating Input Voltage ..36V to 72V
Maximum Input Voltage ....................................... 80V
Output Voltage ..................................................... 12V
Maximum Output Current ...................................... 8A
Output Switching Frequency.............180kHz (typical)
Figure 1. MIC3809 Evaluation Board Schematic
Micrel, Inc. • 2180 Fortune Drive • San Jose, Ca 95131 • USA • tel +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com
January 2005
M9999-080404
(408) 955-1690
Micrel
MIC3809 Evaluation Board
MOSFET is off, thereby preventing current from
flowing through the other. VDS across the off
MOSFET is equal to twice the input voltage. The
voltage across the secondary winding is stepped
down from the primary by the turns ratio of the
transformer. The output inductor and capacitors filter
this voltage. RC snubbers across the primary and
secondary windings dampen high frequency noise
spikes caused by component and circuit parasitics.
Requirements
The evaluation board requires a DC input power
source capable of supplying at least 3.5A at 36V to
obtain maximum power at the output. The output
may be loaded with a resistive or active load. The
active load may be set for constant current or
constant resistance mode.
Precautions
The evaluation board does not have input reverse
polarity protection. Applying a negative voltage at
the +VIN terminal (with respect to the -VIN terminal)
may permanently damage the components on the
board.
The maximum input voltage should be limited to 80
volts to prevent overvoltage stress on the
components.
Getting Started
1) Connect an input voltage source to the +VIN
and -VIN terminals. An ammeter may be
placed between the source and VIN
terminals to monitor input current.
2) Connect a load to the 12V output and GND
terminals. An ammeter may be used in
series with the output.
3) Apply 48 volts at the input. The output
voltage should be 12V.
Figure 2
Startup and Bootstrap Operation
At startup, Q1 and D4 regulate the initial supply
voltage to the MIC3809. The voltage on the base of
Q1 is regulated at one VBE drop lower than the 10V
zener voltage of D4. Including the voltage drop of
D5, VDD at startup is approximately 9V.
A flyback winding on the output inductor provides
the primary side bias voltages. Once the power
supply has started up, this voltage is set higher than
the 9V startup voltage and reverse bias D5 under
normal operation. This improves efficiency by
eliminating power loss in Q1.
VDD1 is filtered to isolate the noise sensitive sections
of the controller from VDD, which supplies power to
the MOSFET gate drive circuit.
Figure 3
Current Sense and Slope Compensation
The MIC3809 uses current mode control. A current
sense transformer senses the primary side current
from both halves of the power transformer which
improves efficiency over using a resistor for current
sensing. A slope compensation ramp must be added
to the current signal since the duty cycle at the
output is greater than 50%. Emitter follower, Q4,
Power Stage
The Push-Pull transformer has split primary and
secondary windings that operate out of phase with
each other. Figures 2 and 3 illustrate the MOSFET
drain-source voltages and drain currents. When one
of the primary MOSFETs is on, driving current
through one of the primary windings, the other
January 2005
2
M9999-080404
(408) 955-1690
Micrel
MIC3809 Evaluation Board
buffers the clock signal ramp and R9/R10 divides
the signal down and mixes the ramp with the current
sense resistor. The voltage across current sense
resistor R3 is shown in the top waveform of Figure 4.
This represents the current through the current
sense transformer. The bottom waveform shows the
voltage as the MIC3809's ISNS pin, which is the
sum of the slope compensation signal and the
voltage across the current sense resistor. For
reference, Figure 5 shows the block diagram of the
MIC3809.
Figure 4
Figure 5
Voltage divider resistors R18/R19 and the internal
Voltage Sensing and Isolation
2.5V reference set the output voltage. VOUT is
The power supply provides safety isolation between
calculated using the formula below:
the input and output. A TL431 senses the output
⎛ R18 ⎞
voltage and compares it to an internal 2.5V
⎟
VOUT = VREF × ⎜ 1+
⎝ R19 ⎠
reference. An opto-isolator sends the control signal,
generated by the TL431 output, across the isolation
Where VREF=2.5V
barrier. This signal is used by the MIC3809 to control
the pulse width of the gate drive signal, which
regulates the output voltage.
January 2005
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Micrel
MIC3809 Evaluation Board
Power Supply Performance
Demo Board
Efficiency
VIN = 48V
12.0595
VIN = 36V
IOUT = 4A
12.0590
89
87
85
12.0585
VOUT (V)
VIN = 72V
83
81
12.0580
12.0575
79
77
75
0 1 2 3 4 5 6 7 8 9 10
OUTPUT CURRENT (A)
12.0570
Figure 8
The power supply transient response and bode plots
are shown in figures 9 through 11. The output
voltage ripple is shown in figure 12.
Bode Plot
12.080
60
12.075
40
12.070
20
VIN = 36V
GAIN (dB)
VOUT (V)
Demo Board
Load Regulation
12.065
VIN = 48V
12.060
0
1 2 3 4 5 6 7
OUTPUT CURRENT (A)
8
150
Phase
100
50
0
0
Gain
-20
-50
Figure 9
Figure 7
January 2005
200
VIN = 48V
-100
-40 VOUT = 12V
-150
IOUT = 8A
-60
-200
10
100
1000 10000 100000
FREQUENCY (Hz)
VIN = 72V
12.055
IOUT = 8A
12.0565
35 40 45 50 55 60 65 70 75
INPUT VOLTAGE (V)
Figure 6
The line and load regulation are shown in Figures 7
and 8.
12.050
IOUT = 1A
PHASE (¡)
EFFICIENCY (%)
95
93
91
Demo Board
Load Regulation
4
M9999-080404
(408) 955-1690
Micrel
MIC3809 Evaluation Board
Figure 10
Figure 11
Figure 12
January 2005
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M9999-080404
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Micrel
MIC3809 Evaluation Board
Bill of Materials
Item
Part Number
Manufacturer
U1
MIC3809BM
(1)
Micrel
U2
PS2703-1(M)
NEC
U3
TL431AIDBVR
TI
C1, C2, C9,
C17
C3216X7R1E105K
TDK
or
GRM21BR71E105KA99L
muRata
C3, C4, C5
C4532X7R2A105M
TDK
Description
(2)
(3)
(4)
(5)
(4)
Voltage Reference
1
1µF, 25V, X7R size 1206
4
1µF, 25V, X7R, 0805
4
0
(5)
1µF, 100V, X7R, 1210
0
1uF, 100V, X7R, 1210
0
220pF, 630V, X7R, 1206
2
(6)
100pF, 50V, 0805, NPO
1
(6)
220pF, 50V, 0805,NPO, 5%
1
(6)
6.8nF, 50V, X7R, 0805, 5%
1
(6)
100µF, 20V, tantalum D case.
4
4.7nF/250AC, X7R, 2220
1
open, Size 0805
3
3.3nF, 50V, X7R,0805, 5%
1
GRM32ER72A105KA01L
muRata
or
12101C105KAZ1A
AVX
(6)
(5)
C6, C7
GRM31BR32J221CKY01L
muRata
C8
VJ0805A101KXAAT
Vishay Vitramon
Vishay Vitramon
C11
VJ0805Y682KXAAT
Vishay Vitramon
C13, C14,
C15, C16
594D107X0020D2T
Vishay Sprague
C18
GA355DR7GC472K
muRata
(5)
C12, C19,
C23
(6)
C20
VJ0805Y332KXAAT
Vishay Vitramon
C21, C22
GRM31BR32J102CKY01L
muRata
(5)
1nF, 250V, X7R, 1206.
2
(6)
0.1µF, 50V, X5R, 0805
1
(6)
1nF, 50V, X7R, 5%, 0805
1
200V, 1A ultrafast
1
C24
VJ0805Y104KXAAT
Vishay Vitramon
C25
VJ0805Y102KXAAT
Vishay Vitramon
D1
ES1D
Diodes Inc.
(7)
(6)
or
ES1D
Vishay
D4
BZT52C10S
Diodes Inc.
0
(7)
10V zener
(6)
1
0
Vishay
D5
SD103AWS
Diodes Inc.
or
SD103AWS
Vishay
(7)
Signal Schottky, 40V
(6)
1
0
D6
1N4148W
Diodes Inc.
or
1N4148W
Vishay
January 2005
1
1µF,100V , X7R, 1206
or
BZX384C10
Opto-Isolator
3
muRata
or
1
1µF, 100V, X7R, 1210
GRM31CR72A105K***L
VJ0805A221KXAAT
MIC3809 push-pull controller
(5)
or
C10
Qty.
(7)
(6)
Signal diode
1
0
6
M9999-080404
(408) 955-1690
Micrel, Inc
MIC3809 Evaluation Board
Bill of Materials (cont.)
Item
Part Number
Manufacturer
D8, D9
30CTQ100S
IR
or
MBRB30H100CT
(8)
Power Schottky, 30A, 100V
0
(10)
Zetex
Q2, Q3
SUD19N20-90
Vishay
(6)
Diodes Inc.
(7)
MMBTA56
T1
CTX04-16236-X2
T2
31333R
L1
CTX04-16235-X1
R1, R2
CRCW080510R0FRT1
Vishay Dale
R3
CRCW08054R99FRT1
Vishay dale
CRCW25121002FRT1
Vishay
Cooper
(9)
Electronics
2
PNP, MMBTA55
1
0
100:1 Current sense x-fmr
1
12µH inductor with bias winding
1
(6)
10Ω
2
(6)
4.99Ω 1%
1
(6)
10kΩ, 1/2W, 5%
1
(6)
33Ω, 1W, 5%
2
(6)
20kΩ
2
(6)
27.4kΩ
1
(6)
17.8kΩ
1
(6)
1kΩ
2
(6)
10kΩ
2
(6)
31.6kΩ
1
(6)
open
3
(6)
499Ω
1
(6)
38.3kΩ
1
(6)
15Ω, 1W
2
(10)
Midcom
Cooper
(9)
Electronics
Vishay dale
Vishay dale
R7, R22
CRCW08052002FRT1
Vishay dale
R8
CRCW08052742FRT1
Vishay dale
R9
CRCW08051782FRT1
Vishay dale
Vishay dale
R11, R19
CRCW08051002FRT1
Vishay dale
R12
CRCW08053162FRT1
Vishay dale
R13, R14,
R16
MOSFET, Nch 200V, 90mohm
1
CRCW251233R0FRT1
CRCW08051001FRT1
1
Push-Pull Transformer
R5, R6
R10, R15
FMMT493 NPN transistor
(6)
or
R4
Vishay dale
R17
CRCW08054990FRT1
Vishay dale
R18
CRCW08053832FRT1
Vishay dale
R20, R21
CRCW251215R0FRT1
Vishay dale
Notes:
Micrel Inc.: 408-944-0800
Vishay Corporation: 206-452-5664
NEC: 408-588-2247
Diodes Inc.: 805-466-4800
TDK: 847-803-6100
IR: 310-252-7105
muRata: 800-831-9172
Cooper Electronics: 888-414-2645
AVX: 843-448-9411
Midcom: 800-643-2661
January 2005
2
Vishay
FMMT493
MMBTA55
Qty.
(6)
Q1
Q4
Description
7
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Micrel, Inc
MIC3809 Evaluation Board
Printed Circuit Boards
Top Silkscreen Overlay
Bottom Silkscreen Overlay
January 2005
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Micrel, Inc
MIC3809 Evaluation Board
Top Layer
Bottom Layer
January 2005
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M9999-080404
(408) 955-1690
Micrel
MIC3809 Evaluation Board
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel
for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a
product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended
for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a
significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a
Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Incorporated.
January 2005
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M9999-080404
(408) 955-1690