1754.PDF

(80 KB) Pobierz
19-1214; Rev 1; 1/98
MAX1620 Evaluation Kit
General Description
The MAX1620 evaluation kit (EV kit) converts a +1.8V to
+12V battery voltage to a +12.5V to +23.5V LCD back-
plane bias voltage for currents up to 20mA. Both the
MAX1620 and MAX1621 include a 5-bit DAC, allowing
digital software control of the bias voltage. The
MAX1620 uses up/down digital signaling to adjust the
DAC, and the MAX1621 uses the System Management
Bus (SMBus™) 2-wire serial interface.
The MAX1620 EV kit is a fully assembled and tested sur-
face-mount circuit board. It can also be used to evaluate
the MAX1621.
o
+1.8V to +12V Battery Input Voltage
o
+12.5V to +23.5V Adjustable Output
o
20mA Output
o
32-Level Internal DAC
o
10µA Shutdown Current
o
Surface-Mount Components
o
Fully Assembled and Tested
Features
Evaluates: MAX1620/MAX1621
Ordering Information
PART
MAX1620EVKIT
TEMP. RANGE
0°C to +70°C
BOARD TYPE
Surface Mount
Component List
DESIGNATION
C1, C6
C2, C3
C5
D1
D4
L1
N1
Q1
R1
R2, R8, R9, R10
R3, R4
R5
R6, R7
R11
U1
JU3
None
JU8
None
QTY
2
2
1
1
1
1
1
1
1
4
2
1
2
1
1
1
1
1
1
DESCRIPTION
22µF, 35V tantalum capacitors
AVX TPSE226M035R0300 or
Sprague 593D226X0035E2T
0.1µF ceramic capacitors
100pF ceramic capacitor
Schottky diode Motorola MBR0540T1
Schottky diode
Central Semiconductor CMPSH-3
100µH inductor Sumida CD54-101
N-channel MOSFET Motorola
MMFT3055VL
2N2907A transistor Central
Semiconductor CMPT2907A
82kΩ, 5% resistor
100kΩ, 5% resistors
300kΩ, 5% resistors
2.2MΩ, 5% resistor
56kΩ, 5% resistors
10kΩ, 5% resistor
MAX1620EEE (QSOP-16)
3-pin header
Shunt (JU3)
2-pin header
MAX1620/MAX1621 PC board
Note: To evaluate the MAX1621, request a free MAX1621EEE
sample with the MAX1620 EV kit.
Component Suppliers
SUPPLIER*
AVX
Central
Semiconductor
Coilcraft
Coiltronics
Dale-Vishay
Motorola
Sprague
Sumida
Vishay/Vitramon
PHONE
803-946-0690
516-435-1110
847-639-6400
561-241-7876
402-564-3131
602-303-5454
603-224-1961
847-956-0666
203-268-6261
FAX
803-626-3123
516-435-1824
847-639-1469
561-241-9339
402-563-6418
602-994-6430
603-224-1430
847-956-0702
203-452-5670
*
Please indicate that you are using the MAX1620 EV kit when
contacting these component suppliers.
Quick Start
The MAX1620 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) Connect a +1.8V to +12V power supply to the
VBATT pad and a +3V to +5.5V supply to the VIN
pad. Connect ground to the GND pad.
2) Connect a voltmeter and load, if any, to the VOUT
pad.
3) Verify the JU3 shunt is across pins 1 and 2 (positive
output).
4) Turn on the power supply and verify that the output
voltage is typically +17.8V.
5) For other output voltages, refer to the
Output Adjustment
section in the MAX1620/MAX1621 data sheet for
instructions on selecting the feedback resistors.
1
None
1
MAX1620/MAX1621 data sheet
Additional components for negative output (included in
1
Shunt
the EV kit) but not installed:
C4
1
1µF ceramic capacitor
C7
D2, D3
1
2
22µF, 35V tantalum capacitor
AVX TPSE226M035R0300 or
Sprague 593D226X0035E2T
Schottky diodes Motorola MBR0540T1
SMBus is a trademark of Intel Corp.
________________________________________________________________
Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1620 Evaluation Kit
Evaluates: MAX1620/MAX1621
_______________Detailed Description
The MAX1620 EV kit converts a +1.8V to +12V battery
voltage to a +12.5V to +23.5V LCD backplane bias volt-
age for currents up to 20mA. The output voltage can be
adjusted with the on-chip DAC, allowing digital software
control of the bias voltage. Up/down digital signaling
adjusts the DAC.
Table 1. Jumper JU8 Settings
SHUNT
LOCATION
On
Off
SHDN
PIN
Connected
to GND
Connected
to VIN
MAX1620 OUTPUT
Shutdown mode, V
OUT
=
V
BATT
, V
OUTSW
= float
MAX1620 enabled,
V
OUT
= +17.8V
Output Voltage Control
The output voltage is set with a voltage divider to the
feedback pin (FB). It can be adjusted with an internal
DAC summing current into FB through an external
resistor. The 5-bit DAC is controlled with a user-pro-
grammable up/down counter. The MAX1620 controls
the DAC counter with the UP and DN pins. A rising
edge on UP increases the output voltage; a rising edge
on DN decreases the output voltage. Holding both UP
and DN high resets the output voltage to mid-range.
Refer to the
Output Voltage Control
section in the
MAX1620/MAX1621 data sheet for more information on
controlling the MAX1620/MAX1621 output voltage.
Controlling the LCD Using POK and
LCDON
POK can be used to turn off a positive LCD bias volt-
age when V
BATT
is too low. A resistor-divider (R1-R2)
from V
BATT
to POK controls the open-drain output,
LCDON,
which pulls low when V
POK
> 1V.
LCDON
drives an external PNP transistor, Q1, switch-
ing a positive V
OUT
to the LCD. Choose a PNP with low
saturation voltage at the required load current. R6 limits
the base current in Q1. R7 is used to turn off Q1 when
LCDON
is floating. R6 and R7 can be the same value.
Refer to the
Controlling the LCD Using POK and
LCDON
section in the MAX1620/MAX1621 data sheet
for instructions on selecting resistors R1, R2, R6, and
R7.
Negative Output Voltage
If a negative output voltage is desired, connect the
MAX1620’s POL pin to ground using jumper JU3. In
this configuration, the error amplifier’s output is inverted
to provide the correct feedback polarity. The feedback
regulation point is 0V. To modify the EV kit for a nega-
tive output voltage:
1) Cut the PC board trace to open jumpers JU1, JU4,
and JU5.
2) Short jumpers JU2, JU6, and JU7 with a piece of
wire.
3) Place the JU3 shunt across pins 2 and 3 (Table 2)
4) Install supplied components D2, D3, C4, and C7.
Table 3 summarizes jumper JU1–JU7 settings.
Evaluating the MAX1621
To evaluate the MAX1621, remove the MAX1620 IC
and resistors R8, R9, and R10.
Table 2. Jumper JU3 Settings
SHUNT
LOCATION
1 and 2
2 and 3
POL PIN
Connected to VIN
Connected to GND
MAX1620 OUTPUT
Positive output,
V
OUT
= +17.8V
Negative output,
V
OUT
= -16.7V
Jumper Selection
Shutdown Mode
The MAX1620 EV kit features a shutdown mode that
reduces the MAX1620 quiescent current to 14µA to
preserve battery life. The two-pin header JU8 selects
the shutdown mode. Table 1 lists the selectable jumper
options.
Positive Output Voltage
This EV kit is shipped with the MAX1620’s polarity pin
(POL) tied to V
IN
for converting to a positive output volt-
age. A boost topology is used, and the feedback regu-
lation point is 1.5V. Refer to the
Output Adjustment
section in the MAX1620/MAX1621 data sheet for
instructions on selecting the feedback resistors.
Table 3. Jumper JU1– JU7 Settings
JUMPER
JU1
JU2
JU3
JU4
JU5
JU6
JU7
POSITIVE OUT
Short
Open
Short 1 and 2
Short
Short
Open
Open
NEGATIVE OUT
Open
Short
Short 2 and 3
Open
Open
Short
Short
2
_______________________________________________________________________________________
VBATT
1.8V TO 12V
R11
10k
PARTS FOR NEGATIVE OUTPUT
D3
MBR0540T1
C4
1µF
D2
MBR0540T1
JU7
VOUT
N1
MMFT3055VL 1
JU4
2
1
JU5
D1
MBR0540T1
Q1
CMPT2907
2
C7
22µF
35V
D4
REF
R1
82k
CMPSH-3
JU6
3
C2
0.1µF
POK
LX
DHI
DLO
PGND
LCDON
DOUT
DOUT
FB
9
R4
300k
R5
2.2M
10
8
13
15
16
REF
V
DD
6
5
BATT
14
L1
100µH
C1
22µF
35V
R2
100k
Figure 1. MAX1620 EV Kit Main Circuit Schematic
U1
MAX1620
11
R8*
100k
4
SHDN (SUS)
UP (SCL)
2
(SUS)
1 DN (SDA)
12
GND
POL
7
V
IN
JU3
1
3
2
(SDA)
JU2
REF
1
JU1
2
R3
300k
R9*
100k
GND
(SCL)
R10*
100k
C5
100pF
VOUTSW
C6
22µF
35V
R7
56k
R6
56k
REF
1.5V
VIN
3V TO 5.5V
C3
0.1µF
V
IN
SHDN
JU8
UP
DN
GND
Evaluates: MAX1620/MAX1621
_______________________________________________________________________________________
* = REQUIRED FOR MAX1620 ONLY.
( ) ARE FOR MAX1621 ONLY.
MAX1620 Evaluation Kit
3
MAX1620 Evaluation Kit
Evaluates: MAX1620/MAX1621
1.0"
Figure 2. MAX1620 EV Kit Component Placement Guide
1.0"
1.0"
Figure 3. MAX1620 EV Kit Component Placement Guide—
Component Side
Figure 4. MAX1620 EV Kit Component Placement Guide—
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.
4
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin