General Description
The MAX1620/MAX1621 convert a 1.8V to 20V battery
voltage to a positive or negative LCD backplane bias
voltage. Backplane bias voltage can be automatically
disabled when the display logic voltage is removed,
protecting the display. These devices use very little PC
board area, come in ultra-small QSOP packages, and
require only small, low-profile external components.
Output voltage can be set to a desired positive or nega-
tive voltage range with external resistors, and adjusted
over that range with the on-board digital-to-analog con-
verter (DAC) or with a potentiometer. The MAX1620/
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 (SMBusTM) 2-wire
serial interface.
These devices use a low-cost, external, N-channel MOSFET
power switch or NPN transistor, and can be configured
for positive or negative output voltages. Operating cur-
rent is a low 150A, typically provided from a display's
logic supply of 3.0V to 5.5V. The MAX1620/MAX1621 are
available in a 16-pin QSOP package.
Applications
Notebook Computers
Palmtop Computers
Personal Digital Assistants
Portable Data-Collection Terminals
Features
o
1.8V to 20V Battery Input Voltage
o
Automatic Disable when Display Logic
is Shut Down
o
Extremely Small QSOP Package
o
32-Level Internal DAC
o
SMBus Serial Interface (MAX1621)
o
Positive or Negative Output Voltage
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
________________________________________________________________
Maxim Integrated Products
1
PART
MAX1620
EEE
MAX1621
EEE
-40C to +85C
-40C to +85C
TEMP. RANGE
PIN-PACKAGE
16 QSOP
16 QSOP
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
Ordering Information
19-1214; Rev 1; 1/98
LX
DHI
DLO
PGND
DOUT
FB
V
DD
POL
SHDN
DN
UP
REF
AGND
MAX1620
12.5V
TO
23.5V OUT
2V TO
12V
3V TO
5.5V
ON
/
OFF
DOWN
UP
LCDON
POK
BATT
Typical Operating Circuit
SMBus is a trademark of Intel Corp.
Pin Configuration
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
DHI
DLO
LX
PGND
AGND
V
DD
DOUT
FB
DN (SDA)
UP (SCL)
BATT
SHDN (SUS)
POK
REF
POL
LCDON
TOP VIEW
MAX1620
MAX1621
QSOP
( ) ARE FOR MAX1621 ONLY.
8
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/MAX1621
Digitally Adjustable LCD Bias Supplies
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= 0C to +85C
, unless otherwise noted.)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
V
DD
to AGND ..............................................................-0.3V to 6V
PGND to AGND ..................................................................0.3V
BATT, LX, LCDON to AGND ....................................-0.3V to 30V
DHI, DLO to PGND.....................................-0.3V to (V
DD
+ 0.3V)
DOUT, FB, POL, POK, REF to AGND.........-0.3V to (V
DD
+ 0.3V)
UP, DN, SHDN to AGND.............................................-0.3V to 6V
SCL, SDA, SUS to AGND............................................-0.3V to 6V
I
DHI
......................................................................................60mA
I
DLO
....................................................................................-30mA
I
LCDON
...............................................................................-10mA
Continuous Power Dissipation (T
A
= +70C)
QSOP (derate 8.3mW/C above +70C) ......................667mW
Operating Temperature Range
MAX1620EEE/MAX1621EEE ............................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10sec) .............................+300C
V
LCDON
= 28V, POK = 0.967V
V
LCDON
= 0.4V, POK = 1.017V
FB = -50mV
FB = REF + 100mV
POL = AGND, 3.0V
V
DD
5.5V
Shutdown mode, V
SHDN
= V
DD
, V
DD
= 5.5V
POL = V
DD
, 3.0V
V
DD
5.5V
Operating mode, output in regulation, V
DD
= 5.5V
V
DD
= 5V
V
DD
= 5V
V
DD
= 3.0V
LX = 12V, shutdown mode
V
DD
= 4.5V
LX = 12V, operating mode
BATT = 12V, shutdown mode
4V
BATT
12V, T
A
= 0C to +85C
BATT = 12V, operating mode
1.8V
BATT
20V, T
A
= +25C
A
1
LCDON High, Leakage Current
mA
-2
-6
LCDON Low, Sinking Current
nA
-10
85
-20
10
FB Input Current (Note 3)
mV
-8
0
8
V
1.46
1.5
1.53
FB Regulation Voltage
mA
-25
DLO Output Current (Note 3)
mA
50
DHI Output Current (Note 3)
14
7
On-Resistance (DLO, DHI)
16.5
23.5
s-V
20
Microsecond-Volt Time Constant (k-factor)
V
27
Positive Output Voltage
9
20
A
150
250
V
DD
Supply Current
1.8
20
BATT Operating Range (Note 2)
1
A
13
20
LX Input Current
A
1
BATT Input Current
-27
Negative Output Voltage
V
1.5
2.8
Undervoltage Lockout Threshold (Note 1)
13
20
V
3.0
5.5
V
DD
Operating Range
Voltage on POK rising
V
0.967
0.992
1.017
POK Threshold Voltage
V
mV
12
POK Hysteresis
CONDITIONS
UNITS
MIN
TYP
MAX
PARAMETER
V
No load
V
1.47
1.5
1.53
REF Voltage
0A
I
REF
25mA
mV
3
10
REF Load Regulation
SWITCHING REGULATOR
REFERENCE AND DAC OUTPUT
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= 0C to +85C
, unless otherwise noted.)
TIMING CHARACTERISTICS
(
T
A
= 0C to +85C
, unless otherwise noted.)
-20A
I
DOUT
0A
I
SDA
= -6mA
V
IN
= 0V or V
IN
= V
DD
V
DD
= 5.5V
V
DD
= 5.5V
3.0V
V
DD
3.6V
3.0V
V
DD
3.6V
48.39mV step size
V
IN
= 0V or V
IN
= V
DD
Guaranteed monotonic
0A
I
DOUT
40A
V
0.4
A
1
SCL, SDA, SUS Input Leakage Current
V
0.6
SCL, SDA, SUS Input Low Voltage
V
2.3
1.4
SCL, SDA, SUS Input High Voltage
1
V
0.6
V
0
0.007
DOUT Minimum Output Voltage (Note 3)
2.3
V
1.4
UP, DN, SHDN, POL Input High Voltage
LSB
DOUT Differential Nonlinearity
Bits
5
DOUT Resolution
1
REF -
REF +
0.02
0.02
DOUT Maximum Output Voltage (Note 3)
V
UP, DN, SHDN, POL Input Leakage Current
A
UP, DN, SHDN, POL Input Low Voltage
SDA Output Low Voltage
CONDITIONS
UNITS
MIN
TYP
MAX
PARAMETER
DIGITAL INPUTS AND OUTPUTS
(Note 4)
(Note 4)
(Note 4)
CONDITIONS
1
SCL Falling Edge to SDA Valid
Master Clocking in Data
s
t
DV
s
4
t
HD:STA
Start Condition SDA to SCL
Hold Time
s
4.7
t
SU:STA
Start Condition SCL to SDA
Setup Time
s
4
t
HIGH
SCL High Time
s
4.7
t
LOW
SCL Low Time
ns
300
t
F
SCL/SDA Fall Time
s
1
t
1
Pulse Width High (UP, DN)
s
1
t
R
SCL/SDA Rise Time
ns
0
t
HD:DAT
SCL to SDA Data-Hold Time
ns
500
t
SU
:
DAT
SDA to SCL Data-Setup Time
s
1
t
2
Pulse Width Low (UP, DN)
s
1
t
3
Pulse Separation (UP, DN)
s
1
t
4
Counter Reset Time
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
s
4
t
SU:STO
Stop Condition SCL_ to SDA_
Setup Time
MAX1620
(Figure 1)
MAX1621
(Figures 2 and 3)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
4
_______________________________________________________________________________________
Operating mode, output in regulation
A
150
250
0A
I
REF
25A
No load
REF Load Regulation
Voltage on POK rising
V
POL = V
DD
, 3.0V
V
DD
5.5V
FB = 0V - 50mV
3.0 5.5
4V
BATT
12V
V
DD
Operating Range
FB = REF + 100mV
POL = AGND, 3.0V
V
DD
5.5V
mV
5
10
V
1.44
1.5
1.56
REF Voltage
V
27
Positive Output Voltage
0.957
0.992
1.027
Shutdown mode, V
SHDN
= V
DD
20
-10
120
FB Input Current (Note 3)
V
DD
Supply Current
V
-30
10
mV
-10
0
10
V
1.5 2.8
Undervoltage Lockout Threshold (Note 1)
nA
1.44
1.5
1.56
s-V
Microsecond-Volt Time Constant (k-factor)
16
24
V
1.8 20
BATT Operating Range (Note 2)
-27
Negative Output Voltage
FB Regulation Voltage
V
POK Threshold Voltage
DOUT Maximum Output Voltage (Note 3)
V
REF -
REF +
0.02
0.02
0A
I
DOUT
40A
-20A
I
DOUT
0A
DOUT Minimum Output Voltage (Note 3)
V
0
0.01
Guaranteed monotonic
DOUT Differential Nonlinearity
LSB
1
UP, DN, SHDN, POL Input High Voltage
3.0V
V
DD
3.6V
1.4
V
DD
= 5.5V
2.3
V
UP, DN, SHDN, POL Input Low Voltage
0.6
V
3.0V
V
DD
3.6V
1.4
V
DD
= 5.5V
2.3
SCL, SDA, SUS Input Low Voltage
0.6
V
SDA Output Low Voltage
I
SDA
= -6mA
0.4
V
CONDITIONS
UNITS
MIN
TYP
MAX
PARAMETER
ELECTRICAL CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= -40C to +85C
. Typical values are at T
A
= +25C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
V
SCL, SDA, SUS Input High Voltage
V
SWITCHING REGULATOR
REFERENCE AND OUTPUT
DIGITAL INPUTS AND OUTPUTS
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
_______________________________________________________________________________________
5
TIMING CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= -40C to +85C
. Typical values are at T
A
= +25C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
CONDITIONS
4
Stop Condition SCL_ to SDA_
Setup Time
s
t
SU:STO
s
4
t
HD:STA
Start Condition SDA_ to SCL_
Hold Time
s
4.7
t
SU:STA
Start Condition SCL_ to SDA_
Setup Time
s
4
t
HIGH
SCL High Time
s
4.7
t
LOW
SCL Low Time
ns
300
t
F
SCL/SDA Fall Time
s
1
t
1
Pulse Width High (UP, DN)
s
1
t
R
SCL/SDA Rise Time
ns
0
t
HD:DAT
SCL_ to SDA_ Data-Hold Time
ns
500
t
SU
:
DAT
SDA_ to SCL_ Data-Setup Time
s
1
t
2
Pulse Width Low (UP, DN)
s
1
t
3
Pulse Separation (UP, DN)
s
1
t
4
Counter Reset Time
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Note 1:
The setting in the DAC is guaranteed to remain valid as long as V
DD
is greater than the UVLO threshold.
Note 2:
BATT Operating Range is guaranteed by the Microsecond-Volt Time Constant specification.
Note 3:
Current sourced from a pin is denoted as positive current. Current sunk into a pin is denoted as negative current.
Note 4:
Guaranteed by design.
__________________________________________Typical Operating Characteristics
(V
DD
= 5V, V
BATT
= 10V, L1 = 100H, T
A
= +25C, unless otherwise noted.)
0.70
0.75
0.80
0.85
0.90
0.95
1.00
0
10
20
30
40
50
60
70
EFFICIENCY vs. OUTPUT CURRENT
MAX1620/21-01
OUTPUT CURRENT (mA)
EFFICIENCY (%)
+25V
+15V
0.70
0.75
0.80
0.85
0.90
0.95
1.00
0
10
20
30
40
50
60
70
EFFICIENCY vs. OUTPUT CURRENT
MAX1620/21-02
OUTPUT CURRENT (mA)
EFFICIENCY (%)
-25V
-15V
0.70
0.75
0.80
0.85
0.90
0.95
1.00
12
14
16
18
20
22
24
26
EFFICIENCY vs. OUTPUT VOLTAGE
MAX1620/21-03
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
+10mA
+20mA
1
SCL Falling Time to SDA Valid
Master Clocking in Data
s
t
DV
MAX1620
(Figure 1)
MAX1621
(Figures 2 and 3)
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