MAX1620EEE ,Digitally Adjustable LCD Bias SuppliesApplicationsNotebook ComputersTypical Operating CircuitPalmtop ComputersPersonal Digital Assistants ..
MAX1620EEE+ ,Digitally Adjustable LCD Bias SuppliesApplicationsNotebook ComputersTypical Operating CircuitPalmtop ComputersPersonal Digital Assistants ..
MAX1620EEE-T ,Digitally Adjustable LCD Bias SuppliesFeaturesThe MAX1620/MAX1621 convert a 1.8V to 20V battery♦ 1.8V to 20V Battery Input Voltagevoltage ..
MAX1621EEE ,Digitally Adjustable LCD Bias SuppliesFeaturesThe MAX1620/MAX1621 convert a 1.8V to 20V battery' 1.8V to 20V Battery Input Voltagevoltage ..
MAX1621EEE+ ,Digitally Adjustable LCD Bias SuppliesELECTRICAL CHARACTERISTICS(V = 3.3V, V = 10V, T = 0°C to +85°C, unless otherwise noted.)DD BATT APA ..
MAX1623EAP ,3A / Low-Voltage / Step-Down Regulator with Synchronous Rectification and Internal SwitchesELECTRICAL CHARACTERISTICS(V = V = +5V, FBSEL unconnected, R = 110kΩ, T = 0°C to +85°C, unless othe ..
MAX4359EAX+ ,Low-Cost 4x4, 8x4, 8x8 Video Crosspoint SwitchesApplications40 Plastic DIPMAX4456EPL -40°C to +85°C P40-1High-Speed Signal Video Test Equipment44 P ..
MAX435CPD ,Wideband Trasconductance AmplifiersGeneral Description
The MAX435 and MAX436 are high-speed, wideband
transconductance amplifiers ..
MAX435CPD ,Wideband Trasconductance AmplifiersELECTRICAL CHARACTERISTICS - MAX435
(V+ = W, V- = -5v, -2.5vs IN+ s 2.5V, -2.5V s IN- s 2.5V, ZL+ ..
MAX435CPD+ ,Wideband Trasconductance AmplifiersGeneral Description
The MAX435 and MAX436 are high-speed, wideband
transconductance amplifiers ..
MAX435EPD ,Wideband Trasconductance Amplifiers19-0042; Rev 1; 4/93
[VI lle/VI
Wideband 'rransetondluctamte Amplifiers
MAX435ESD ,Wideband Trasconductance Amplifiersapplications, sucn a5 lllgll'apku "F%Pbtbr0r's'''""'"''"' -
plitiers and wideband, high-gain bandp ..
MAX1620EEE-MAX1621EEE
Digitally Adjustable LCD Bias Supplies
General DescriptionThe 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.
ApplicationsNotebook Computers
Palmtop Computers
Personal Digital Assistants
Portable Data-Collection Terminals
Features1.8V to 20V Battery Input VoltageAutomatic Disable when Display Logic
is Shut DownExtremely Small QSOP Package32-Level Internal DACSMBus Serial Interface (MAX1621)Positive or Negative Output Voltage
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
Typical Operating Circuit
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= 3.3V, VBATT= 10V, TA
= 0°C to +85°C, 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.
VDDto AGND..............................................................-0.3V to 6V
PGND to AGND..................................................................±0.3V
BATT, LX, LCDONto AGND....................................-0.3V to 30V
DHI, DLO to PGND.....................................-0.3V to (VDD+ 0.3V)
DOUT, FB, POL, POK, REF to AGND.........-0.3V to (VDD+ 0.3V)
UP, DN, SHDNto AGND.............................................-0.3V to 6V
SCL, SDA, SUSto AGND............................................-0.3V to 6V
IDHI......................................................................................60mA
IDLO....................................................................................-30mA
ILCDON...............................................................................-10mA
Continuous Power Dissipation (TA= +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
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
ELECTRICAL CHARACTERISTICS (continued)(VDD= 3.3V, VBATT= 10V, TA
= 0°C to +85°C, unless otherwise noted.)
TIMING CHARACTERISTICS (TA
= 0°C to +85°C, unless otherwise noted.)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
ELECTRICAL CHARACTERISTICS
(VDD= 3.3V, VBATT= 10V, TA= -40°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
TIMING CHARACTERISTICS
(VDD= 3.3V, VBATT= 10V, TA= -40°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted. Limits over this
temperature range are guaranteed by design.)
Note 1:The setting in the DAC is guaranteed to remain valid as long as VDDis 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
(VDD= 5V, VBATT= 10V, L1 = 100µH, TA= +25°C, unless otherwise noted.)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
_____________________________Typical Operating Characteristics (continued)
(VDD=5V, VBATT= 10V, L1 = 100µH, TA= +25°C, unless otherwise noted.)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
_____________________________Typical Operating Characteristics (continued)
(VDD=5V, VBATT= 10V L1 = 100µH, VOUT= 22.3V, TA= +25°C, unless otherwise noted.)
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
Figure 1. MAX1620 UP and DN Signal Timing
Figure 2. MAX1621 SMB Serial-Interface Timing—Address
Figure 3. MAX1621 SMB Serial-Interface Timing—Acknowledge
MAX1620/MAX1621
Digitally Adjustable LCD Bias Supplies
_______________Detailed Description
The MAX1620/MAX1621 are step-up power controllers
that drive an external N-channel FET or NPN transistor
to convert power from a 1.8V to 20V battery to a higher
positive or negative voltage. They are configured as
negative-output, inverting power controllers with one
additional diode and one additional capacitor. Either
configuration’s output voltage can be adjusted with
external resistors, or digitally adjusted with an internal
digital-to-analog converter (DAC). The MAX1620 uses
pin-defined controls for the DAC, while the MAX1621
communicates with the DAC via the SMBus™ interface.
Operating Principle
The MAX1620/MAX1621 operate in discontinuous-
conduction mode (where the inductor current ramps to
zero by the end of each switching cycle) and with a
constant peak current, without requiring a current-
sense resistor. Switch on-time is inversely proportional
to the input voltage VBATTby a microsecond-volt con-
stant, or k-factor, of 20µs-V (e.g., for VBATT= 10V,
on-time = 2µs).
For an ideal boost converter operating in discontinu-
ous-conduction mode (no power losses), output current
is proportional to input voltage and peak inductor current:
IPKis proportional to on-time (tON), which, for these
parts, is determined by the k-factor:
IPK= k-factor / L
Discontinuous conduction is detected by monitoring the
LX node voltage. When the inductor’s energy is com-
pletely delivered, the LX node voltage snaps back to
the BATT voltage. When this crossing is sensed, anoth-
er pulse is issued if the output is still out of regulation.
Positive Output Voltage
To select a positive output voltage, tie the polarity pin
(POL) to VDDand use the typical boost topology shown
in Figure 4. FB regulation voltage is 1.5V. For optimum
stability, VOUTshould be greater than 1.1 (VBATT).
Negative Output Voltage
To select a negative output voltage, tie POL to GND
(Figure 5). In this configuration, the internal error amplifi-
er’s output is inverted to provide the correct feedback
polarity. FB regulation voltage is 0V. D1, D2, C4, and C5
form an inverting charge pump to generate the negative
voltage. This allows application of the positive boost
switching topology to negative output voltages.
The negative output circuit has two possible connec-
tions. In the standard connection, D1’s cathode is con-
nected to BATT. This connection features the best
output ripple performance, but ‰VOUT‰must be limited
to no more than 27V - 1.1(VBATT). If a larger negative
voltage is needed, an alternative connection allows a
maximum negative output of -27V, but with the addition-
al constraint that ‰VOUT‰> 1.1VBATT. To use the alter-
native circuit, connect D1’s cathode to ground rather
than BATT (Figure 6). Increase C4 to 2.2mF to improve
output ripple performance.
The negative charge pump limits the output current to
the charge transferred each cycle multiplied by the
Figure 4. Typical Operating Circuit—Positive Output
