Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - power management - special purpose QSOP 16

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.

Applications

Notebook Computers

Palmtop Computers

Personal Digital Assistants

Portable Data-Collection Terminals

Features

♦ 1.8V to 20V Battery Input Voltage

♦ Automatic Disable when Display Logic

is Shut Down

♦ Extremely Small QSOP Package

♦ 32-Level Internal DAC

♦ SMBus Serial Interface (MAX1621)

♦ Positive or Negative Output Voltage

MAX1620/MAX1621

Digitally Adjustable LCD Bias Supplies

________________________________________________________________

Maxim Integrated Products

PART

MAX1620EEE

MAX1621EEE

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 QSOP

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Ordering Information

19-1214; Rev 1; 1/98

DHI

DLO

PGND

DOUT

POL

SHDN

REF

AGND

MAX1620

12.5V

23.5V OUT

2V TO

12V

3V TO

5.5V

OFF

DOWN

LCDONPOK

BATT

Typical Operating Circuit

SMBus is a trademark of Intel Corp.

Pin Configuration

DHI

DLO

PGND

AGND

DOUT

DN (SDA)

UP (SCL)

BATT

SHDN (SUS)

POK

REF

POL

LCDON

TOP VIEW

MAX1620

MAX1621

QSOP

( ) ARE FOR MAX1621 ONLY.

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.

Summary of content (20 pages)

PAGE 1
9-1214; Rev 1; 1/98 NUAL KIT MA ATION EET H S A EVALU T WS DA O L L O F Digitally Adjustable LCD Bias Supplies 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.
PAGE 2
MAX1620/MAX1621 Digitally Adjustable LCD Bias Supplies ABSOLUTE MAXIMUM RATINGS VDD 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 (VDD + 0.3V) DOUT, FB, POL, POK, REF to AGND.........-0.3V to (VDD + 0.3V) UP, DN, SHDN to AGND..............................
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Digitally Adjustable LCD Bias Supplies (VDD = 3.3V, VBATT = 10V, TA = 0°C to +85°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS V DOUT Maximum Output Voltage (Note 3) 0µA ≤ IDOUT ≤ 40µA REF 0.02 REF + 0.02 DOUT Minimum Output Voltage (Note 3) -20µA ≤ IDOUT ≤ 0µA 0 0.007 DOUT Resolution 48.39mV step size 5 DOUT Differential Nonlinearity Guaranteed monotonic V Bits ±1 LSB DIGITAL INPUTS AND OUTPUTS UP, DN, SHDN, POL Input High Voltage 3.0V ≤ VDD ≤ 3.6V 1.
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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.) PARAMETER CONDITIONS MIN TYP MAX UNITS 5.5 V 150 250 SWITCHING REGULATOR VDD Operating Range VDD Supply Current 3.
PAGE 5
Digitally Adjustable LCD Bias Supplies (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.
PAGE 6
_____________________________Typical Operating Characteristics (continued) (VDD = 5V, VBATT = 10V, L1 = 100µH, TA = +25°C, unless otherwise noted.) -10mA 0.80 -20V, -10mA 0.85 0.80 0.75 0.70 0.70 MAX1620/21-06 MAX1620/21-05 +20V, +10mA 0.90 0.75 200 180 160 SUPPLY CURRENT (µA) -20mA 0.85 0.95 EFFICIENCY (%) 0.95 EFFICIENCY (%) 1.00 MAX1620/21-04 1.00 0.90 SUPPLY CURRENT vs. SUPPLY VOLTAGE EFFICIENCY vs. VBATT EFFICIENCY vs.
PAGE 7
Digitally Adjustable LCD Bias Supplies (VDD = 5V, VBATT = 10V L1 = 100µH, VOUT = 22.3V, TA = +25°C, unless otherwise noted.) k-FACTOR vs. VBATT MAX1620/21-13 25 24 k-FACTOR (µs-V) 23 22 21 20 19 18 17 16 15 0 5 10 15 20 VBATT (V) LOAD-TRANSIENT RESPONSE LINE-TRANSIENT RESPONSE MAX1620/21-15 MAX1620/21-14 VOUT (AC COUPLED, 5mV/div) VOUT (AC COUPLED, 20mV/div) 5.3V 20mA VDD (AC COUPLED, 1V/div) IOUT (10mA/div) 3.
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Digitally Adjustable LCD Bias Supplies MAX1620/MAX1621 ______________________________________________________________Pin Description PIN NAME 8 FUNCTION MAX1620 MAX1621 1 — DN Logic-Level Input. A rising edge on DN decreases VOUT. UP = DN = high resets the counter to mid-scale. — 1 SDA System Management Bus Serial-Data Input and Open-Drain Output 2 — UP Logic-Level Input. A rising edge on UP increases VOUT. UP = DN = high resets the counter to mid-scale.
PAGE 9
Digitally Adjustable LCD Bias Supplies t2 MAX1620/MAX1621 t1 t4 UP t3 DN Figure 1. MAX1620 UP and DN Signal Timing MOST SIGNIFICANT ADDRESS BIT (A6) CLOCKED INTO SLAVE START CONDITION A5 CLOCKED INTO SLAVE A3 CLOCKED INTO SLAVE A4 CLOCKED INTO SLAVE SCL tHD:STA tLOW tHIGH tSU:STO SDA tSU:STA tSU:DAT tHD:DAT tSU:DAT tHD:DAT Figure 2.
PAGE 10
_______________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).
PAGE 11
Digitally Adjustable LCD Bias Supplies R8 10k C3 22µF L1 100µH D1 MBRS0540 D3 1N6263 (ANY SCHOTTKY) TO REF 3V TO 5.5V C1 0.1µF C2 0.1µF 3 5 11 7 4 1 2 6 12 U1 BATT POK VDD MAX1620 MAX1621 POL SHDN (SUS) DN (SDA) UP (SCL) REF AGND LX DHI DLO PGND DOUT FB LCDON C4 1µF 14 16 15 13 MAX1620/MAX1621 2V TO 15V D2 MBRS0540 C5 22µF -6V TO -12V OUT N1 MMFT3055VL R3 300k 10 9 R5 1.2M 8 R4 300k ( ) ARE FOR MAX1621. C6 100pF NOTE: CONNECTIONS TO DIGITAL INPUTS NOT SHOWN. Figure 5.
PAGE 12
MAX1620/MAX1621 Digitally Adjustable LCD Bias Supplies The MAX1620 controls the DAC counter with the UP and DN pins. A rising edge on UP increases VOUT by decrementing the counter and decreasing the DAC output voltage one step; a rising edge on DN decreases V OUT  by incrementing the counter and increasing the DAC output voltage one step. Holding both UP and DN high resets the counter to half-scale. The counter will not roll over at either the FS or ZERO code.
PAGE 13
Digitally Adjustable LCD Bias Supplies BIT NAME Table 2. MAX1621 Configuration Byte with REGSEL = 1 (write to OPR register) POR STATE* DESCRIPTION 7 POR STATE* DESCRIPTION REGSEL — Register Select. A one in this bit writes the next two bits into the OPR register and the remaining five bits into the DAC register (Figure 7). BIT NAME 7 REGSEL — Register Select. A zero in this bit writes the next two bits into the SUS register and the remaining five bits into the DAC register (Figure 7).
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MAX1620/MAX1621 Digitally Adjustable LCD Bias Supplies MOST SIGNIFICANT ADDRESS BIT START CONDITION LEAST SIGNIFICANT ADDRESS BIT SLAVE ACKNOWLEDGE SLAVE ACKNOWLEDGE MOST SIGNIFICANT R/W BIT DATA BIT LEAST SIGNIFICANT DATA BIT SCL SUS-SHDN REGSEL SDA DAC DATA D4 D3 D2 D1 D0 SUS-LCDON SLAVE PULLS SDA LOW SLAVE PULLS SDA LOW Figure 7.
PAGE 15
Digitally Adjustable LCD Bias Supplies MAX1620/MAX1621 LEAST SIGNIFICANT ADDRESS BIT MOST SIGNIFICANT ADDRESS BIT SLAVE ACKNOWLEDGE MOST SIGNIFICANT R/W BIT DATA BIT START CONDITION SCL POK SDA D4 D3 D2 D1 D0 SLAVE PULLS SDA LOW MAX1621 DRIVES SDA Figure 9. MAX1621 Serial-Interface Read Example Design Procedure __________and Component Selection The MAX1620/MAX1621 output voltage can be adjusted manually or via a digital interface.
PAGE 16
MAX1620/MAX1621 Digitally Adjustable LCD Bias Supplies Setting the Maximum Output Voltage (DAC Adjustment) The DAC is adjustable from 0V to 1.5V in 32 steps, and 1LSB = 1.5V / 31. DAC adjustment of VOUT is provided by adding R3 to the divider circuit (Figure 4). Be sure that VOUT,MAX does not exceed the LCD panel rating. For VOUT,MAX = 25V and VOUT,MIN = 12.5V, R3 is determined as follows: R3 = R5 x (VFB) / (VOUT,MAX - VOUT,MIN) = 2.2MΩ x (1.5) / (25 - 12.
PAGE 17
Digitally Adjustable LCD Bias Supplies coil inductance; however, for most inductor types, the coil’s specified current can be exceeded by 20% with no impact on efficiency. The peak current is set by the coil inductance as follows: IPK = k-factor / L and R7 ≤ 50 x (12.5 - 0.7) / 10mA = 59kΩ IOUT,MIN = Remember that LCD voltage is the regulated output voltage minus the drop across the PNP switch. The drop across the external transistor (typically 300mV) must be accounted for.
PAGE 18
MAX1620/MAX1621 Digitally Adjustable LCD Bias Supplies Diode Selection Input Bypass Capacitor The high maximum switching frequency of 300kHz requires a high-speed rectifier. Schottky diodes, such as the MBRS0540, are recommended. To maintain high efficiency, the average current rating of the Schottky diode must be greater than the peak switching current. Choose a reverse breakdown voltage greater than the positive output voltage or greater than the negative output voltage plus VBATT.
PAGE 19
Digitally Adjustable LCD Bias Supplies L1 220µH D3 1N6263 (ANY SCHOTTKY) TO REF R2 100k 3V TO 5.5V C3 10µF R8 10k R1 360k 3 5 11 7 4 1 2 6 12 C1 0.1µF C2 0.1µF U1 BATT POK VDD MAX1620 MAX1621 POL SHDN (SUS) DN (SDA) UP (SCL) REF AGND LX DHI DLO PGND DOUT FB LCDON D1 MBRS0540+ RS 470Ω 14 16 15 13 C5 10µF R6 150k Q1 MMBT4401LT1 R3 300k 10 9 R5 2.2M 12.5V TO 23.5V OUT Q1 MMBT2907 R7 150k VOUTSW R4 300k 8 C6 100pF ( ) ARE FOR MAX1621. NOTE: CONNECTIONS TO DIGITAL INPUTS NOT SHOWN.
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________________________________________________________Package Information QSOP.