MAXIM MAX8550_0411

19-3436; Rev 1; 11/04
MAX8550 Evaluation Kit
The MAX8550 evaluation kit (EV kit) is designed to evaluate the MAX8550 DDR power-supply solution for notebooks, desktops, and graphics cards. The EV kit board
produces VDDQ at the output of the synchronous PWM
buck, VTT at the output of the sourcing/sinking LDO linear
regulator, and VTTR at the output of the reference buffer.
The VDDQ output is preset to 2.5V and sources up to
12A. The VTT output is always VDDQ/2 and can
source/sink up to 3A of peak current and 1.5A of continuous current. The VTTR output is also always VDDQ/2
and can source/sink up to 10mA.
The MAX8550 EV kit was conveniently designed with
jumpers to select the OVP/UVP, TON, SKIP, STBY, and
SHDN_ modes. The board’s default settings enable
OVP (overvoltage protection), 600kHz switching frequency, low-noise PWM mode, VDDQ, VTT, and VTTR.
The VIN input accepts voltages from 9V to 20V and
VDD requires a 5V bias supply.
The EV kit comes with the MAX8550 installed. Contact
the factory for free samples of the MAX8550A or
MAX8551 to evaluate these parts.
Features
♦ VDDQ Preset to 2.5V/12A
♦ VTT 1.25V Source/Sink 1.5A Continuous/3A Peak
♦ VTTR 1.25V Source/Sink 10mA
♦ VIN Range: 9V to 20V
♦ Optimized Switching Frequency: 600kHz
♦ Overvoltage/Undervoltage Protection
♦ Standby
♦ Independent Shutdown
♦ Power OK
Ordering Information
PART
TEMP RANGE
IC PACKAGE
MAX8550EVKIT
0°C to +70°C
28 Thin QFN 5mm x 5mm
Note: To evaluate the MAX8550A, request a free sample of the
MAX8550AETI when ordering the MAX8550 EV kit. To evaluate
the MAX8551, request a free sample of the MAX8551ETI when
ordering the MAX8550 EV kit.
Component List
DESIGNATION QTY
DESCRIPTION
1
0.1µF ±10%, 50V X7R ceramic
capacitor (0603)
TDK C1608X7R1H104K
C2, C4A, C4B,
C4C, C4D,
C4E, C4F
7
10µF ±10%, 6.3V X5R ceramic
capacitors (1206)
TDK C3216X5R0J106K or
TDK C3216X5R0J106M
C3, C6, C13
3
1µF ±10%, 10V X5R ceramic
capacitors (0603)
TDK C1608X5R1A105K
C5
1
4.7µF ±20%, 6.3V X5R ceramic
capacitor (0805)
TDK C2012X5R0J475M
C1
C7, C10
C8A, C8B, C8C
DESIGNATION QTY
DESCRIPTION
C8D
0
Not installed
470µF ±20%, 25V aluminum
electrolytic capacitor (10mm x 16mm)
Sanyo 25MV470WX
C9
1
3900pF, 50V X7R ceramic capacitor
(0603)
Kemet C0603C392K5RAC
C11, C12
2
150µF, 4V, 25mΩ low-ESR POS
capacitors (D2E)
Sanyo 4TPE150M
C14
1
470pF ±5%, 50V COG ceramic
capacitor (0603)
TDK C1608COG1H471J
C15, C16
2
Not installed (0603)
2
0.22µF ±20%, 16V X7R ceramic
capacitors (0603)
TDK C1608X7R1C224M
D1
1
Schottky diode, 30V, 100mA (SOD-323)
Central CMDSH-3
JU1, JU2
2
4-pin headers
3
10µF ±20%, 25V X5R ceramic
capacitors (1210)
Taiyo Yuden TMK325BJ106MM
TDK C3225X5R1E106M
JU3–JU6
4
3-pin headers
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
Evaluates: MAX8550/MAX8550A/MAX8551
General Description
Evaluates: MAX8550/MAX8550A/MAX8551
MAX8550 Evaluation Kit
Component List (continued)
DESIGNATION QTY
DESCRIPTION
L1
1
1.0µH, 20A, 1.6mΩ power inductor
(12.6mm x 12.6mm x 5.2mm)
TOKO FDA1254-1R0M
Q1
1
n-channel MOSFET 30V, 9mΩ (SO-8)
International Rectifier IRF7821
Q2
1
n-channel MOSFET 30V, 5mΩ (SO-8)
International Rectifier IRF7832
R1
1
10Ω ±5% resistor (0603)
R2, R3
2
100kΩ ±5% resistors (0603)
R4
1
75kΩ ±1% resistor (0603)
R5
1
124kΩ ±1% resistor (0603)
R6, R7, R8
2
Not installed (0603)
R9, R10, R11
3
0Ω resistors (0603)
R12
1
Not installed (1812)
R13
1
20Ω ±5% resistor (0603)
U1
1
MAX8550ETI (28-pin 5mm x 5mm Thin
QFN)
None
6
Shunts
None
1
MAX8550 EV kit PC board
Component Suppliers
SUPPLIER
PHONE
WEBSITE
Central
Semiconductor
631-435-1110 www.centralsemi.com
International
Rectifier
310-322-3331 www.irf.com
Kemet
864-963-6300 www.kemet.com
Sanyo USA
619-661-6835 www.sanyo.com
TDK
847-803-6100 www.component.tdk.com
TOKO America
847-297-0070 www.tokoam.com
Note: Indicate that you are using the MAX8550 when contacting these component suppliers.
Recommended Equipment
• 5VDC power supply (500mA rated)
• 9VDC to 20VDC power supply (5A rated)
• Two digital voltmeters (DVM)
2
Quick Start
The MAX8550 EV kit is fully assembled and tested. Follow
these steps to verify board operation. Do not turn on the
power supplies until all connections are completed.
1) Ensure a shunt is placed across pins 1-4 of jumper
JU1 to enable OVP and UVP.
2) Ensure a shunt is placed across pins 1-2 of jumper
JU2 to set the switching frequency to approximately
600kHz.
3) Ensure a shunt is placed across pins 1-2 of jumper
JU3 to enable low-noise PWM mode.
4) Ensure a shunt is placed across pins 2-3 of jumper
JU4 to disable the VDDQ buck output.
5) Ensure a shunt is placed across pins 1-2 of jumper
JU5 to enable the VTT and VTTR outputs.
6) Ensure a shunt is placed across pins 2-3 of jumper
JU6 to set the board in normal operation mode.
7) Connect the 5VDC power supply across the VDD
pad and the PGND pad nearest VIN.
8) Connect the 12VDC power supply across the VIN
pad and the corresponding PGND pad.
9) Turn on both of the power supplies.
10)Set JU4 (1-2). This turns VDDQ on.
11)Using one of the DVMs, verify that the VDDQ voltage
between the VDDQ and PGND pads is 2.5V (±2%).
12)Using the other DVM, verify that the VTT voltage
between the VTT and PGND pads is 1.25V (±2%).
Detailed Description
Jumper Selection
Table 1. Overvoltage/Undervoltage
Control Input (OVP/UVP)
JUMPER
SHUNT
POSITION
JU1
1-2
Disable OVP and UVP.
JU1
1-3
Enable UVP. Disable OVP.
JU1
1-4*
Enable OVP and UVP.
JU1
Open
DESCRIPTION
Enable OVP. Disable UVP.
*Default position.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on OVP/UVP. This mode does
not directly apply to the MAX8551.
_______________________________________________________________________________________
MAX8550 Evaluation Kit
SHUNT
POSITION
DESCRIPTION
JU2
1-2*
600kHz switching frequency
JU2
1-3
450kHz switching frequency
JU2
1-4
200kHz switching frequency
JU2
Open
300kHz switching frequency
JUMPER
Table 5. Shutdown Control Input B
(SHDNB)
JUMPER
SHUNT
POSITION
JU5
1-2*
The VTT and VTTR outputs are
enabled.
JU5
2-3
The VTT and VTTR outputs are
shut down.
*Default position.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on TON.
Table 3. Pulse-Skipping Control Input
(SKIP)
JUMPER
SHUNT
POSITION
JU3
1-2*
Low-noise PWM mode.
2-3
Pulse-skipping mode.
Use only this position when
evaluating the MAX8551.
JU3
DESCRIPTION
DESCRIPTION
*Default position.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on SHDNB. SHDNB is TP0 on
the MAX8550A.
Caution: Do not connect an external controller to the
SHDNB pad while a shunt is on jumper JU5.
Table 6. Standby Control Input (STBY)
JUMPER
SHUNT
POSITION
DESCRIPTION
JU6
1-2
The VTT output is shut down.
JU6
2-3*
Normal operation.
*Default position.
*Default position.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on SKIP.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on STBY. STBY is STBY on the
MAX8550A.
Caution: Do not connect an external controller to the
SKIP pad while a shunt is on jumper JU3.
Table 4. Shutdown Control Input A
(SHDNA)
JUMPER
SHUNT
POSITION
DESCRIPTION
JU4
1-2
The VDDQ buck output is enabled.
JU4
2-3*
The VDDQ buck output is shut
down.
*Default position.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data
sheet for additional information on SHDNA. SHDNA is SHDN
on the MAX8550A.
Caution: Do not connect an external controller to the
SHDNA pad while a shunt is on jumper JU4.
Caution: Do not connect an external controller to the
STBY pad while a shunt is on jumper JU6.
Setting the Buck Regulator Output
Voltage (VDDQ)
The output voltage of the buck regulator is preset to
2.5V on the MAX8550 EV kit for DDR memory applications. To pin-strap the output voltage to 1.8V follow the
steps below:
1) Remove R9.
2) Solder the 0Ω resistor from step 1 in the R7 location.
Refer to the MAX8550/MAX8551 data sheet to change
the external components for optimum performance.
Low-Side MOSFET Snubber Circuit (Buck)
Fast switching transitions cause ringing because of the
resonating circuit formed by the parasitic inductance
and capacitance at the switching LX node. This highfrequency ringing occurs at the LX node’s rising and
_______________________________________________________________________________________
3
Evaluates: MAX8550/MAX8550A/MAX8551
Table 2. On-Time Selection Input (TON)
Evaluates: MAX8550/MAX8550A/MAX8551
MAX8550 Evaluation Kit
falling transitions and may interfere with circuit performance and generate EMI. To dampen this ringing, an
optional series RC snubber circuit is added across the
low-side switch. Below is a simple procedure for selecting the value of the series RC for the snubber circuit:
1) Connect a scope probe to the LX node labeled on
the MAX8550 EV kit schematic and observe the ringing frequency, fR.
2) Estimate the circuit parasitic capacitance (CPAR) at
LX by first finding a capacitor value, which, when
connected from LX to PGND1, reduces the ringing
frequency by half. CPAR can then be approximated
as 1/3 the value of the capacitor value found.
3) Estimate the circuit parasitic inductance (LPAR) from
the equation:
LPAR =
4
1
4) Calculate R12 for critical dampening from the equation:
R12 = 2π × fR x LPAR
Adjust the resistor value up or down to tailor the
desired damping and the peak voltage excursion.
5) Capacitor C15 should be at least 2 to 4 times the
value of CPAR to be effective.
The power loss of the snubber circuit (PWR_SNUB) is
dissipated in the resistor and can be calculated as:
PWR_SNUB = C15 x VIN2 x fSW
where VIN is the input voltage and fSW is the switching
frequency. Choose the power rating of R12 according
to the specific application’s derating rule for the power
dissipation calculated in the equation above.
Recommended snubber values for this EV kit are 3Ω
(R12) and 2.2nF (C15).
(2π × fR )2 × CPAR
_______________________________________________________________________________________
_______________________________________________________________________________________
PGND
C4A
10µF
POK2
POK1
4
REF
R9
0Ω
R6
OPEN
2
4
1
POK2
POK1
TON
FB
ILIM
VDDQ
R8
OPEN
16 OUT
15
R7
OPEN
4
REF
24 GND
3
REFIN
VTTI
MAX8550
14
13
OVP/UVP
VTTR
PGND2
8 SS
6
5
1
2
10
11
R4
75kΩ
1%
AVDD
C9
3900pF
JU1
3
C4F
10µF
C16
OPEN
AVDD
R5
124kΩ
1%
REF
C4E
10µF
C10
0.22µF
R3
100kΩ
R2
100kΩ
1
AVDD
C6
1µF
C4D
10µF
JU2 2
3
C14
470pF
REF
C4C
10µF
AVDD
GND
VTTR
C4B
10µF
VTT
9
VTTS
12
C1
0.1µF
R13
20Ω
VDDQ
SKIP
25
DL
DH
VIN
LX
BST
VDD
AVDD
STBY
SHDNB
SHDNA
PGND1
1
JU3 2
3
SKIP
7
3
3
1
2
AVDD
1
2
6
5
1
2
3
1
2
VIN
L1
1µH
C8A
10µF
LX
C15
OPEN
STBY
C12
150µF
C8C
10µF
VDDQ
C13
1µF
STBY SHDNA SHDNB VDDQ
ON
1
0
1
0
0
1
ON
ON
1
1
1
1
OFF
0
0
0
OFF
0
0
VTT
ON
OFF
OFF
ON
OFF
VTTR
ON
OFF
ON
ON
OFF
PGND
VDDQ
2.5 AT 12A
PGND
VIN
(9V TO 20V)
C8D
OPEN
ON/OFF CONTROL LOGIC
C8B
10µF
C5
4.7µF
VDD
(5V BIAS SUPPLY)
C11
R12 150µF
OPEN
SHDNB
SHDNA
3
AVDD
JU6
3
1
2
AVDD
JU4
R11
0Ω
7
Q2
IRF7832 8
4
4
6
5
C7
0.22µF
D1
CMDSH-3
C3
1µF
Q1
7
IRF7821 8
R10
0Ω
R1
10Ω
LX
28 JU5
27
23
21
18
17
19
20
22
26
AVDD
Evaluates: MAX8550/MAX8550A/MAX8551
VTT
C2
10µF
VDDQ
MAX8550 Evaluation Kit
Figure 1. MAX8550 EV Kit Schematic
5
Evaluates: MAX8550/MAX8550A/MAX8551
MAX8550 Evaluation Kit
Figure 2. MAX8550 EV Kit Component Placement Guide—Component Side
Figure 3. MAX8550 EV Kit PC Board Layout—Component Side
6
_______________________________________________________________________________________
MAX8550 Evaluation Kit
Evaluates: MAX8550/MAX8550A/MAX8551
Figure 4. MAX8550 EV Kit PC Board Layout—Inner Layer 2 (GND, PGND1 and PGND2)
Figure 5. MAX8550 EV Kit PC Board Layout—Inner Layer 3 (GND, PGND1 and PGND2)
_______________________________________________________________________________________
7
Evaluates: MAX8550/MAX8550A/MAX8551
MAX8550 Evaluation Kit
Figure 6. MAX8550 EV Kit PC Board Layout—Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 8
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.