General Description The MAX668 evaluation kit EV kit combines a con stant frequency pulse width modulation PWM step up controller with an external N channel MOSFET and Schottky diode to provide a regulated output voltage The EV kit accepts a +3V to VOUT input and converts it to a +12V output for currents up to 1A with greater than conversion efficiency The EV kit operates at 500kHz allowing the use of small external components The MAX668 EV kit is a fully assembled and tested sur face mount circuit board This EV kit can also be con figured for the application circuits listed in the EV Kit Application Circuit Capabilities table For input voltages below 3V and down to 8V replace the MAX668 with a MAX669 The MAX669 must always operate in boot strapped mode JU2 shunt across pins and

19-4778; Rev 0a; 8/98
MAX668 Evaluation Kit
General DescriptionFeatures
The MAX668 evaluation kit (EV kit) combines a con-
©
+3V to V
OUT
Input Range (as shipped)
stant-frequency, pulse-width-modulation (PWM) step-
©
+12V or Adjustable Output Voltage
up controller with an external N-channel MOSFET and
Schottky diode to provide a regulated output voltage.
©
Output Current Up to 1A
The EV kit accepts a +3V to V
OUT
input and converts it
©
N-Channel External MOSFET
to a +12V output for currents up to 1A, with greater than
90% conversion efficiency. The EV kit operates at
©
4µA IC Shutdown Current
500kHz, allowing the use of small external components.
©
500kHz Switching Frequency
The MAX668 EV kit is a fully assembled and tested sur-
©
Surface-Mount Components
face-mount circuit board. This EV kit can also be con-
©
Fully Assembled and Tested
figured for the application circuits listed in the EV Kit
Application Circuit Capabilitiestable. For input voltages
below 3V and down to 1.8V, replace the MAX668 with a
Component List
MAX669. The MAX669 must always operate in boot-
strapped mode (JU2 shunt across pins 1 and 2).
DESIGNATIONQTYDESCRIPTION
68µF, 20V, low-ESR tantalum cap
C11Sprague 593D686X0020E2W or
AVX TPSE686M020R0150
Ordering Information
120µF, 20V, low-ESR tantalum cap
PARTTEMP. RANGEIC PACKAGE
C51Sprague 594D127X0020R2T
MAX668EVKIT0°C to +70°C10 µMAXC210.1µF ceramic capacitor
Note:
To evaluate the MAX669, request a MAX669EUB freeC310.22µF ceramic capacitor
sample with the MAX668EVKIT.C4, C821µF ceramic capacitors
C71220pF ceramic capacitor
C60Not installed
3A Schottky diode
EV Kit Application Circuit
D11Hitachi HRF302A or
Capabilities
Motorola MBRS340T3
4.7µH power inductor
V
IN(MIN)
V
OUT
I
OUT
L11Sumida CDRH104-4R7 (shielded),
(V)(V)(A)
Coiltronics UP2B-4R7, or
1.8120.4Coilcraft DO3316P-472
1.8240.1N-channel MOSFET
N11Fairchild FDS6680 or
2.5120.65International Rectifier IRF7801
33531210.020
½
, 1%, 1/2W resistor
3360.02R11Dale WSL-2010-R020F or
IRC LR2010-01-R020F
12240.5R21218k
½
, 1% resistor
Note:
Design information for these applications is included. R3124.9k
½
, 1% resistor
The shaded row shows EV kit configuration as shipped.R41100k
½
, 1% resistor
U11MAX668EUB
JU1, JU223-pin headers
JU312-pin header
None2Shunts (JU1, JU2)
None1MAX668/MAX669 PC board
None1MAX668/MAX669 data sheet
________________________________________________________________Maxim Integrated Products1
For free samples & the latest literature: http:
/
www.maxim-ic.com, or phone 1-800-998-8800.
For sma
l
orders, phone 408-737-7600 ext. 3468.

MAX668 Evaluation Kit

Component Suppliers
SUPPLIERPHONEFAX
AVX803-946-0690803-626-3123
CoilCraft708-639-6400708-639-1469
Coiltronics561-241-7876561-241-9339
Dale-Vishay402-564-3131402-563-6418
Fairchild408-721-2181408-721-1635
Hitachi888-777-0384650-244-7947
IRnetecrtinfiaetrional310-322-3331310-322-3332
IRC512-992-7900512-992-3377
Motorola602-303-5454602-994-6430
Siliconix408-988-8000408-970-3950
Sprague603-224-1961603-224-1430
Sumida708-956-0666708-956-0702
Vishay/Vitramon203-268-6261203-452-5670
Note:
Please indicate that you are using the MAX668 when con-
tacting these component suppliers.
_________________________Quick Start
The MAX668 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)Place the shunt on JU1 across pins 1 and 2. Verify
that the shunt is across JU2 pins 2 and 3 (V
CC
is
tied to V
IN
) and JU3 is open (LDO is open).
2)Connect a +5V supply to the V
IN
pad. Connect
ground to the GND pad.
3)Connect a voltmeter to the V
OUT
pad.
4)Turn on the power supply and verify that the output
voltage is 12V.
_______________Detailed Description
The MAX668 EV kit provides a regulated +12V output
voltage from an input source as low as +3V. It drives
loads up to 1A with greater than 90% conversion effi-
ciency. This EV kit is shipped configured in the non-
bootstrapped mode (V
CC
is tied to V
IN
). However, there
are several methods of connecting V
CC
and LDO
depending on the specific design including input and
output voltage range, quiescent power dissipation,
MOSFET selection, and load.

If the minimum input voltage is below +3.0V, use the
MAX669 with V
CC
bootstrapped from V
OUT
(Table 1). In
bootstrapped mode, if V
OUT
is always less than +5.5V,
then LDO may be shorted to V
CC
to eliminate the
dropout voltage of the LDO regulator. This increases the
gate drive to the MOSFET, which lowers the MOSFET
on-resistance but increases the MAX668 supply current
due to gate-charge loss.
If V
IN
is greater than +3.0V, the MAX668’s V
CC
can be
powered from V
IN
. This will decrease quiescent power
dissipation, especially when V
OUT
is large. If V
IN
is
always less than +5.5V, LDO may be shorted to V
CC
to
eliminate the dropout voltage of the LDO regulator. If
V
IN
is in the range of +3V to +4.5V, then the user may
still want to bootstrap from V
OUT
to increase gate drive
to the MOSFET at the expense of power dissipation. If
V
IN
is always greater than +4.5V, the V
CC
input should
always be tied to V
IN
, since bootstrapping from V
OUT
will not increase the gate drive from LDO, but quiescent
power dissipation will rise. Jumpers JU2 and JU3 con-
trol the V
CC
and LDO inputs (see MAX668/MAX669
data sheet).
Jumper Selection
The 3-pin header JU1 selects shutdown mode. Table 1
lists the selectable jumper options. The 3-pin header
JU2 selects bootstrapped mode. Table 2 lists the
selectable jumper options. For V
CC
less than 5.5V, use
the 2-pin header JU3 to short LDO to V
CC
. This elimi-
nates the internal linear regulator (LDO) dropout volt-
age. For the MAX668, this allows operation with input
voltages down to 2.7V. Table 3 lists the selectable
jumper options.
Other Output Voltages
The MAX668 EV kit can also be used to evaluate other
output voltages. Refer to the Output Voltage Selection
section in the MAX668 data sheet for instructions on
selecting the feedback resistors R2 and R3.
For output
voltages greater than 15V, replace C5 (20V) with a
capacitor that has a higher voltage rating.
In addition to the standard EV kit configuration of 3V
IN
to 12V
OUT
at 1A, the EV Kit Application Circuit
Capabilitiestable listed several common Input/Output
combinations. Table 4 lists the components recom-
mended for these alternative circuits.

2_______________________________________________________________________________________

Table 1. Jumper JU1 Functions
SHUNT
LOCATIONSYNC/
SHDN
PIN
1 and 2Connected to V
CC
2 and 3Connected to GND
Not installedFloating

Table 2. Jumper JU2 Functions
LOSCHAUTNITO NV
CC
PIN
1 and 2Connected to V
OUT
2 and 3Connected to V
IN

Table 3. Jumper JU3 Functions
SHUNT LOCATIONLDO PIN
OnConnected to V
CC
OffOpen

MAX668 Evaluation Kit

MAX668 OUTPUT
MMAAXX666688 oepnearblaeteds, Vat
O
i
U
n
T
te=r n1a2l Vfr. equency.
Shutdown mode, V
OUT
= V
IN
- diode
SMYANXC6/6
S
8
H
c
D
a
N
n pbae de ixst ecrlnoacllkye sd.ynchronized when the

MAX668 MODE
Bootstrapped mode
Non-bootstrapped mode

_______________________________________________________________________________________3

MAX668 Evaluation Kit

Table 4. Components for Alternate Application Circuits
2UJV
IN
MAXIMBOOT-
(MIN)
V(
O
V
U
)
T
I(
O
A
U
)
T
PARTSTRvAsP.PED(µLH1)(mR
½
1)(kR
½
2)(kR
½
3)(kR
½
4)D1N1C1C5C6
(V)NO.NON-BOOT-
STRAPPED
4.7 2068µF120µF
1 & 2SumidaDaleHitachiInternational20V20V
1.8120.4MAX669BootstrappedCDRH10WSL-21824.9100HRF302ARectifierAVXSpragueOpen
4-4R72010-IRF7401TPSE686M594D127X
R020F020R01500020R2T
1568µF22µF22µF
1 & 2Coi1l.c0raftDaleHitachiInternational20V35V35V
1.8240.1MAX669BootstrappedD03316-2W0S1L0--45424.9200HRF302AIRReFc7ti4fi0e1rTPSAEV6X86MTPSAEV2X26MTPSAEV2X26M
102R015F020R0150035R0300035R0300
4.7 2068µF120µF
1 & 2SumidaDaleHitachiInternational20V20V
2.5120.65MAX669BootstrappedCDRH10WSL-21824.9100HRF302ARectifierAVXSpragueOpen
4-4R72010-IRF7401TPSE686M594D127X
R020F020R01500020R2T
4.7 15330µF330µF330µF
1 & 2SumidaDaleHitachiFairchild10V10V10V
353MAX668BootstrappedCDRH122W5S1L2--7524.9100HRF502AFDS6680T5K1e0mX3et37T5K1e0mX3et3