19-2876; Rev 0; 5/03
MAX1955 Evaluation Kit
General Description
The MAX1955 evaluation kit (EV kit) is a fully assembled
and tested circuit board for evaluating the MAX1955 dual-
PWM step-down controller. The board comes with the
MAX1955 installed, but can also be used to evaluate the
MAX1956.
The EV kit is configured to operate from a 2.25V to 5.5V
input supply range and provides 1.8V and 1.5V outputs
capable of delivering 25A each. By changing appropriate
external components, the output voltage can be set from
0.8V to 0.9 x V
IN
. By using the MAX1956, the input supply
range can be extended from 1.6V to 5.5V.
Features
o
Configured for 1.8V and 1.5V Outputs
o
MAX1955: 2.25V to 5.5V Input Supply Range
o
MAX1956: 1.6V to 5.5V Input Supply Range
o
Up to 25A Current for Each Output
o
±4% Voltage Margining
o
Foldback Current Limit
o
Selectable Voltage Sequencing
o
Independent ON/OFF Control
o
Synchronizable to an External Clock
o
Fully Assembled and Tested
Evaluates: MAX1955/MAX1956
Ordering Information
PART
TEMP RANGE
IC PACKAGE
28 Thin QFN 5mm x 5mm
MAX1955EVKIT 0°C to +70°C
Component List
DESIGNATION
QTY
DESCRIPTION
10µF
±20%,
6.3V X5R ceramic
capacitors (0805)
Panasonic ECJ2FB0J106M
or Taiyo Yuden JMK212BJ106MG
0.47µF ±20%, 10V X5R ceramic
capacitors (0603)
Taiyo Yuden LMK107BJ474MA
Not installed, POSCAPs
680µF, 2.5V, 8mΩ POSCAPs
Sanyo 2R5TPD680M8
Not installed (0603)
470µF, 6.3V POSCAPs
Sanyo 6TPB470M
0.015µF ±10%, 25V X7R ceramic
capacitors (0603)
Taiyo Yuden TMK107B153KZ
4700pF ±10% X7R ceramic
capacitors (0603)
Murata GRM188R71H472K
6800pF ±10% X7R ceramic
capacitors (0603)
Murata GRM188R71H682K
33pF ±0.1pF, 50V C0G ceramic
capacitors (0603)
Murata GRM1885C1H330J
DESIGNATION
C28
QTY
1
DESCRIPTION
0.22µF ±10%, 10V X7R ceramic
capacitor (0603)
Taiyo Yuden LMK107BJ224KA
82pF ±5%, 50V C0G ceramic
capacitors (0402)
Murata GRP1555C1H820J
4.7µF ±10%, 6.3V X5R ceramic
capacitor (0603)
Panasonic ECJ1VB0J475K or
equivalent
Schottky diodes (SOT323)
Central Semiconductor CMSSH-3
Not installed (SMC)
Central Semiconductor CMSH5-20
Not installed, scope probe
connectors
3-pin headers
2-pin headers
0.3µH, 35A, 1.5mΩ inductors
Sumida CDEP125(U)-0R3
4.7µH inductor
TDK LDR655312T-4R7W
N-channel MOSFETs
(8-pin SO PowerPak)
Vishay Si7892DP
C1–C7
7
C31, C32
2
C8, C9, C29
C10, C17
C11, C12, C13,
C18
C14, C16
C15, C33
3
0
4
0
2
C34
1
D1–D4
D5, D6
J1–J4
JU1, JU2, JU3
JU4, JU5
L1, L2
4
0
0
3
2
2
1
C19, C20
2
C21, C22, C23,
C30
4
C24, C27
2
L3
C25, C26
2
N1, N2, N8, N9
4
________________________________________________________________
Maxim Integrated Products
1
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.
MAX1955 Evaluation Kit
Evaluates: MAX1955/MAX1956
Component List (continued)
DESIGNATION
N3, N4, N7,
N10
N5, N6, N11,
N12
Q1, Q2
R1, R23
R2
R3, R6
R4
R5, R20, R21,
R22, R25–R28
R7
R8
QTY
0
4
2
0
1
2
1
8
1
1
DESCRIPTION
Not installed (8-pin SO)
N-channel MOSFETs (8-pin SO)
Vishay Si4842DY
NPN transistors (SOT23)
ON Semiconductor MMBT3904LT1
Not installed (0603)
7.15kΩ ±0.1% resistor (0603)
8.06kΩ ±0.1% resistors (0603)
10kΩ ±0.1% resistor (0603)
1Ω ±5% resistors (0603)
15kΩ ±5% resistor (0603)
18kΩ ±5% resistor (0603)
DESIGNATION
R9, R14
R10
R11
R12
R13
R15, R16, R17
R18
R19
R24
R29–R32
U1
—
—
—
QTY
2
1
1
1
1
0
1
1
1
4
1
5
4
1
DESCRIPTION
100kΩ ±1% resistors (0603)
200kΩ ±1% resistor (0603)
60.4kΩ ±1% resistor (0603)
56.2kΩ ±1% resistor (0603)
10Ω ±5% resistor (0603)
Not installed (0603), PC board shorts
75kΩ ±1% resistor (0603)
90.9kΩ ±1% resistor (0603)
510Ω ±5% resistor (0603)
10kΩ ±5% resistors (0603)
MAX1955ETI
Shunts, position 2
Rubber feet
MAX1955 EV kit PC board
Component Suppliers
SUPPLIER
Central Semiconductor
International Rectifier
Murata
Panasonic
Sanyo
Sumida
Taiyo Yuden
TDK
Vishay
PHONE
631-435-1110
310-322-3331
814-237-1431
714-373-7939
619-661-6835
847-545-6700
408-573-4150
847-803-6100
408-970-5715
www.irf.com
www.murata.com
www.panasonic.com
www.sanyo.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.vishay.com
WEBSITE
www.centralsemi.com
Note:
Please indicate that you are using the MAX1955/MAX1956 when contacting these component suppliers.
Quick Start
The MAX1955 EV kit is fully assembled and tested. Follow
these steps to verify board operation.
Do not turn on the
power supply until all connections are completed:
1) Verify the shorts on JU2 and JU3 are across pins 2
and 3.
2) Verify the pins of JU4 and JU5 are not shorted.
3) Preset the input power supply to between 2.25V and
5.5V.
4) Turn the power supply off.
5) Connect the positive power-supply terminal to the EV
kit pads labeled IN.
6) Connect the power-supply ground to the EV kit pads
labeled PGND.
7) Connect a load and voltmeter from OUT1 to PGND
and another load and voltmeter from OUT2 to PGND.
8) Turn on the input power supply and verify the voltage
from OUT1 to PGND is 1.5V and the voltage from
OUT2 to PGND is 1.8V.
2
_______________________________________________________________________________________
MAX1955 Evaluation Kit
Detailed Description
Evaluating the MAX1956
The MAX1955 EV kit comes with the MAX1955 installed,
but can also be used to evaluate the MAX1956. To evalu-
ate the MAX1956, carefully remove the MAX1955 from the
PC board and replace it with the MAX1956. After
installing the MAX1956, inspect all connections with an
ohmmeter to verify there are no solder bridges or open
connections before powering up the EV kit.
Clock Synchronization Input (SYNC)
The MAX1955 EV kit can be synchronized to an external
clock from 1080kHz to 1320kHz. Connect the clock
signal to SYNC and connect the clock-signal ground to
GND. Each of the step-down controllers switch at 1/2
the frequency applied to SYNC and are 180° out-of-
phase with each other. To use the internal clock, leave
SYNC unconnected, and each controller switches at
600kHz and is 180° out-of-phase with each other.
Evaluates: MAX1955/MAX1956
Setting the Output Voltages
The MAX1955 uses a pair of feedback resistors to set the
output voltage for each output. In the MAX1955 EV kit,
OUT1 is preset to 1.5V and OUT2 is preset to 1.8V. Each
output can be set to any voltage from 0.8V to 0.9 x V
IN
.
Use the following procedure to change the output voltage:
1) Change the upper feedback resistors (R2 and R4) to
set the output voltage. Use the following formulas to
calculate the values of the resistors:
V
R2
=
R 3
OUT1
−
1
0.8
where R3 is 8.06kΩ and V
OUT1
is the desired output
voltage of OUT1, and:
V
R4
=
R6
OUT2
−
1
0.8
where R6 is 8.06kΩ and V
OUT2
is the desired output
voltage of OUT2.
2) The output capacitors on the MAX1955 EV kit are
rated for 2.5V. For higher output voltages, higher
voltage-rated capacitors should be used.
3) Change the current-limit resistors (R11 and R18 for
OUT1, R12 and R19 for OUT2). Refer to the
MAX1955/MAX1956 data sheet for information on
calculating values for these resistors.
4) Refer to the MAX1955/MAX1956 data sheet to select
the optimum inductor, output capacitors, and com-
pensation components.
Output Sequencing (SEQ)
The outputs can be set to power up at the same time,
or OUT1 can be set to power up first and power down
last. For simultaneous power-up/-down, short pins 1
and 2 of JU1 (Table 1). To make OUT1 power up first
and power down last, short pins 2 and 3 of JU1.
Evaluating Voltage Margining
A voltage-margining feature is provided on the
MAX1955 and MAX1956. This allows the output volt-
ages to be shifted up or down by 4%. Voltage margin-
ing is controlled by JU2 and JU3 (Table 2). To ensure
proper startup, verify that JU2 and JU3 are shorted
between pins 2 and 3 (normal operation) when power is
first applied to the EV kit.
Evaluating Shutdown
Shutdown mode turns off the IC and reduces the input
current. JU2 and JU3 control the shutdown feature (Table
2). There are also individual shutdown inputs provided on
the EV kit (EN1 and EN2). These inputs allow each output
to be shut down individually, but do not completely power
down the IC. For convenience, jumpers are provided to
control the EN_ inputs. With no connection to the EN_
pads, short the pins of JU4 and JU5 to shut down OUT1
and OUT2, respectively. Remove the short to enable the
outputs (Tables 3 and 4). To control individual shutdown
with a logic source, remove the shorts from JU4 and JU5
and connect the logic source to the EN_ pad. Drive EN_
logic high for shutdown or logic low to enable the output.
Refer to the MAX1955/MAX1956 data sheet for details.
_______________________________________________________________________________________
3
MAX1955 Evaluation Kit
Evaluates: MAX1955/MAX1956
Table 1. JU1 Functions
JU1
POSITION
1 and 2
2 and 3
SEQ
CONNECTION
GND
VDD
SEQUENCING
OUT1 and OUT2 power
up/down simultaneously
OUT1 powers up first and
powers down last
Table 3. JU4 Functions
JU4 POSITION
OPEN
SHORT
OUT1 shutdown
FUNCTION
OUT1 enabled or controlled from
EN2
input
Table 4. JU5 Functions
JU5 POSITION
FUNCTION
OUT2 enabled or controlled from
EN2
input
OUT2 shutdown
OPEN
SHORT
Table 2. JU2 and JU3 Functions
JU2 POSITION
1 and 2
1 and 2
2 and 3
2 and 3
JU3 POSITION
1 and 2
2 and 3
1 and 2
2 and 3
FUNCTION
Shutdown
-4% margining
+4% margining
Enable (normal operation)
4
_______________________________________________________________________________________
IN
C33
470µF
V
IN
C34
4.7µF
23
D1
25
LXB
V
IN
C8
0.47µF
4
BST1
V
DD
L3
4.7µH
R15
SHORT
C15
470µF
C1
10µF
C2
10µF
C3
10µF
R24
510Ω
IN
R21
1Ω
C23
4700pF
3
N3
L1
0.3µH
LX1
R26
1Ω
C19
0.015µF
U1
LX1P
R2
7.15kΩ
R1
26
N6
28
22
R3
8.06kΩ
C31
82pF
VIN
3
2
1
JU3
C24
6800pF
JU2
R10
200kΩ
3
2
1
R9
100kΩ
R7
15kΩ
C25
33pF
6
EN
5
17
R14
100kΩ
VDD
JU1
3 2 1
D3
8
N5
N4
DL1
PGND
PGND1
PGND2
FB1
C30
4700pF
D5
1
R27
1Ω
R22
1Ω
2
N2
N1
DH1
OUT1
C10
C11
680µF
C16
C12
680µF
Figure 1. MAX1955 EV Kit Schematic (Sheet 1 of 2)
MAX1955
9
COMP1
SYNC
SEQ
R29
10kΩ
EN1
JU4
IN
R30
10kΩ
Q1
J1
CTL2
CTL1
SYNC
Evaluates: MAX1955/MAX1956
_______________________________________________________________________________________
PGND
MAX1955 Evaluation Kit
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
