19-1214; Rev 1; 1/98
UAL
IT MAN
TION K
A
ET
EVALU
TA SHE
WS DA
FOLLO
Digitally Adjustable LCD Bias Supplies
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 (SMBus™) 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 150µA, 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.
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
Features
MAX1620/MAX1621
Ordering Information
PART
MAX1620EEE
MAX1621EEE
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Applications
Notebook Computers
Palmtop Computers
Personal Digital Assistants
Portable Data-Collection Terminals
Typical Operating Circuit
2V TO
12V
Pin Configuration
TOP VIEW
DN (SDA) 1
UP (SCL) 2
BATT 3
SHDN (SUS) 4
POK 5
REF 6
POL 7
LCDON 8
16 DHI
15 DLO
14 LX
ON
/
OFF
DOWN
UP
3V TO
5.5V
V
DD
POL
BATT
LX
DHI
DLO
PGND
12.5V
TO
23.5V OUT
SHDN
DN
UP
MAX1620
MAX1621
13 PGND
12 AGND
11 V
DD
10 DOUT
9
FB
MAX1620
REF
AGND
POK
DOUT
FB
LCDON
( ) ARE FOR MAX1621 ONLY.
QSOP
SMBus is a trademark of Intel Corp.
________________________________________________________________
Maxim Integrated Products
1
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.
Digitally Adjustable LCD Bias Supplies
MAX1620/MAX1621
ABSOLUTE MAXIMUM RATINGS
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
= +70°C)
QSOP (derate 8.3mW/°C above +70°C) ......................667mW
Operating Temperature Range
MAX1620EEE/MAX1621EEE ............................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
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.
ELECTRICAL CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
SWITCHING REGULATOR
V
DD
Operating Range
V
DD
Supply Current
Positive Output Voltage
Negative Output Voltage
Undervoltage Lockout Threshold (Note 1)
BATT Input Current
LX Input Current
BATT Operating Range (Note 2)
Microsecond-Volt Time Constant (k-factor)
On-Resistance (DLO, DHI)
DHI Output Current (Note 3)
DLO Output Current (Note 3)
FB Regulation Voltage
FB Input Current (Note 3)
LCDON
Low, Sinking Current
LCDON
High, Leakage Current
POK Threshold Voltage
POK Hysteresis
REFERENCE AND DAC OUTPUT
REF Voltage
REF Load Regulation
2
No load
0µA
≤
I
REF
≤
25mA
1.47
1.5
3
1.53
10
V
mV
1.8V
≤
BATT
≤
20V, T
A
= +25°C
4V
≤
BATT
≤
12V, T
A
= 0°C to +85°C
V
DD
= 4.5V
V
DD
= 3.0V
V
DD
= 5V
V
DD
= 5V
POL = V
DD
, 3.0V
≤
V
DD
≤
5.5V
POL = AGND, 3.0V
≤
V
DD
≤
5.5V
FB = REF + 100mV
FB = -50mV
V
LCDON
= 0.4V, POK = 1.017V
V
LCDON
= 28V, POK = 0.967V
Voltage on POK rising
0.967
0.992
12
1.46
-8
-20
-10
-2
-6
1
1.017
16.5
7
14
50
-25
1.5
0
1.53
8
10
85
BATT = 12V, operating mode
BATT = 12V, shutdown mode
LX = 12V, operating mode
LX = 12V, shutdown mode
1.8
20
23.5
13
1.5
13
Operating mode, output in regulation, V
DD
= 5.5V
Shutdown mode, V
SHDN
= V
DD
, V
DD
= 5.5V
3.0
150
9
5.5
250
20
27
-27
2.8
20
1
20
V
µA
V
V
V
µA
µA
V
µs-V
Ω
mA
mA
V
mV
nA
mA
µA
V
mV
CONDITIONS
MIN
TYP
MAX
UNITS
1
20
_______________________________________________________________________________________
Digitally Adjustable LCD Bias Supplies
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
DOUT Maximum Output Voltage (Note 3)
DOUT Minimum Output Voltage (Note 3)
DOUT Resolution
DOUT Differential Nonlinearity
DIGITAL INPUTS AND OUTPUTS
UP, DN,
SHDN,
POL Input High Voltage
UP, DN,
SHDN,
POL Input Low Voltage
UP, DN,
SHDN,
POL Input Leakage Current
SCL, SDA,
SUS
Input High Voltage
SCL, SDA,
SUS
Input Low Voltage
SCL, SDA,
SUS
Input Leakage Current
SDA Output Low Voltage
V
IN
= 0V or V
IN
= V
DD
I
SDA
= -6mA
V
IN
= 0V or V
IN
= V
DD
3.0V
≤
V
DD
≤
3.6V
V
DD
= 5.5V
1.4
2.3
0.6
±1
0.4
3.0V
≤
V
DD
≤
3.6V
V
DD
= 5.5V
1.4
2.3
0.6
±1
V
V
µA
V
V
µA
V
CONDITIONS
0µA
≤
I
DOUT
≤
40µA
-20µA
≤
I
DOUT
≤
0µA
48.39mV step size
Guaranteed monotonic
MIN
REF -
0.02
0
5
±1
TYP
MAX
REF +
0.02
0.007
UNITS
V
V
Bits
LSB
MAX1620/MAX1621
TIMING CHARACTERISTICS
(T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
MAX1620
(Figure 1)
Pulse Width High (UP, DN)
Pulse Width Low (UP, DN)
Pulse Separation (UP, DN)
Counter Reset Time
MAX1621
(Figures 2 and 3)
SDA to SCL Data-Setup Time
SCL to SDA Data-Hold Time
SCL/SDA Rise Time
SCL/SDA Fall Time
SCL Low Time
SCL High Time
Start Condition SCL to SDA
Setup Time
Start Condition SDA to SCL
Hold Time
Stop Condition SCL_ to SDA_
Setup Time
SCL Falling Edge to SDA Valid
Master Clocking in Data
t
SU
:
DAT
t
HD:DAT
t
R
t
F
t
LOW
t
HIGH
t
SU:STA
t
HD:STA
t
SU:STO
t
DV
(Note 4)
(Note 4)
(Note 4)
4.7
4
4.7
4
4
1
500
0
1
300
ns
ns
µs
ns
µs
µs
µs
µs
µs
µs
t
1
t
2
t
3
t
4
1
1
1
1
µs
µs
µs
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
_______________________________________________________________________________________
3
Digitally Adjustable LCD Bias Supplies
MAX1620/MAX1621
ELECTRICAL CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= -40°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
PARAMETER
SWITCHING REGULATOR
V
DD
Operating Range
V
DD
Supply Current
Positive Output Voltage
Negative Output Voltage
Undervoltage Lockout Threshold (Note 1)
BATT Operating Range (Note 2)
Microsecond-Volt Time Constant (k-factor)
FB Regulation Voltage
FB Input Current (Note 3)
POK Threshold Voltage
REFERENCE AND OUTPUT
REF Voltage
REF Load Regulation
DOUT Maximum Output Voltage (Note 3)
DOUT Minimum Output Voltage (Note 3)
DOUT Differential Nonlinearity
DIGITAL INPUTS AND OUTPUTS
UP, DN,
SHDN,
POL Input High Voltage
UP, DN,
SHDN,
POL Input Low Voltage
SCL, SDA,
SUS
Input High Voltage
SCL, SDA,
SUS
Input Low Voltage
SDA Output Low Voltage
I
SDA
= -6mA
3.0V
≤
V
DD
≤
3.6V
V
DD
= 5.5V
1.4
2.3
0.6
0.4
3.0V
≤
V
DD
≤
3.6V
V
DD
= 5.5V
1.4
2.3
0.6
V
V
V
V
V
No load
0µA
≤
I
REF
≤
25µA
0µA
≤
I
DOUT
≤
40µA
-20µA
≤
I
DOUT
≤
0µA
Guaranteed monotonic
REF -
0.02
0
1.44
1.5
5
1.56
10
REF +
0.02
0.01
±
1
CONDITIONS
MIN
3.0
TYP
MAX
5.5
UNITS
V
µA
V
V
V
V
µs-V
V
mV
nA
V
V
mV
V
V
LSB
Operating mode, output in regulation
Shutdown mode, V
SHDN
= V
DD
150
250
20
27
-27
1.5
1.8
4V
≤
BATT
≤
12V
POL = V
DD
, 3.0V
≤
V
DD
≤
5.5V
POL = AGND, 3.0V
≤
V
DD
≤
5.5V
FB = REF + 100mV
FB = 0V - 50mV
Voltage on POK rising
16
1.44
-10
-30
-10
0.957
0.992
1.5
0
2.8
20
24
1.56
10
10
120
1.027
4
_______________________________________________________________________________________
Digitally Adjustable LCD Bias Supplies
TIMING CHARACTERISTICS
(V
DD
= 3.3V, V
BATT
= 10V,
T
A
= -40°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
PARAMETER
MAX1620
(Figure 1)
Pulse Width High (UP, DN)
Pulse Width Low (UP, DN)
Pulse Separation (UP, DN)
Counter Reset Time
MAX1621
(Figures 2 and 3)
SDA_ to SCL_ Data-Setup Time
SCL_ to SDA_ Data-Hold Time
SCL/SDA Rise Time
SCL/SDA Fall Time
SCL Low Time
SCL High Time
Start Condition SCL_ to SDA_
Setup Time
Start Condition SDA_ to SCL_
Hold Time
Stop Condition SCL_ to SDA_
Setup Time
SCL Falling Time to SDA Valid
Master Clocking in Data
Note 1:
Note 2:
Note 3:
Note 4:
t
SU
:
DAT
t
HD:DAT
t
R
t
F
t
LOW
t
HIGH
t
SU:STA
t
HD:STA
t
SU:STO
t
DV
4.7
4
4.7
4
4
1
500
0
1
300
ns
ns
µs
ns
µs
µs
µs
µs
µs
µs
t
1
t
2
t
3
t
4
1
1
1
1
µs
µs
µs
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1620/MAX1621
The setting in the DAC is guaranteed to remain valid as long as V
DD
is greater than the UVLO threshold.
BATT Operating Range is guaranteed by the Microsecond-Volt Time Constant specification.
Current sourced from a pin is denoted as positive current. Current sunk into a pin is denoted as negative current.
Guaranteed by design.
__________________________________________Typical Operating Characteristics
(V
DD
= 5V, V
BATT
= 10V, L1 = 100µH, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
MAX1620/21-01
EFFICIENCY vs. OUTPUT CURRENT
MAX1620/21-02
EFFICIENCY vs. OUTPUT VOLTAGE
MAX1620/21-03
1.00
0.95
EFFICIENCY (%)
0.90
+25V
0.85
0.80
0.75
0.70
0
10
20
30
40
50
60
1.00
0.95
EFFICIENCY (%)
0.90
-25V
0.85
0.80
0.75
0.70
-15V
1.00
0.95
+20mA
EFFICIENCY (%)
0.90
0.85
0.80
0.75
0.70
+10mA
+15V
70
0
10
20
30
40
50
60
70
12
14
16
18
20
22
24
26
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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