Rainbow Electronics MAX6948B User Manual

19-4935; Rev 0; 9/09

EVALUATION KIT

AVAILABLE

High-Efficiency PWM LED Driver with Boost

Converter and Five Constant-Current GPIO Ports

General Description

The MAX6948B general-purpose input/output (GPIO)
peripheral drives a series string of white LEDs (WLEDs),
and contains up to five general-purpose input/output
(GPIO) ports to drive additional LEDs.

The integrated 2MHz boost converter minimizes the size
and cost of external components and supplies 30mA of
load current at up to 28V. The converter is stable under
all load conditions from 5V up to 28V and includes
open-circuit detection to prevent damage to the IC. An
I2C-programmable 10-bit pulse-width modulation (PWM)
signal enables 1024 levels of WLED intensity.

The five GPIO ports function as logic inputs, open­drain logic outputs, or constant-current sinks in any
combination. Ports withstand 5.5V independent of the
MAX6948B’s supply voltage. Two of the ports drive addi­tional LEDs up to 30mA/port, while the other three ports
drive LEDs at up to 10mA/port. The MAX6948B features
shutdown and standby modes for low-power dissipa­tion. The constant-current drivers contain programmable
PWM outputs and allow staggering to reduce the input
peak-current requirements. The I/O ports also feature
ramp-up and ramp-down controls.

The MAX6948B features a single input to select from four
I2C slave addresses. Programming and functionality for
the five GPIO ports is identical to the MAX6946/MAX6947
I/O expanders.

The MAX6948B is available in a 25-bump (2.31mm x

2.31mm) WLP package for cell phones, PDAs, and
other portable consumer electronic applications. The
MAX6948B operates over the -40NC to +105NC tempera­ture range.

Applications

LED Backlighting for LCDs

Cell Phones

PDAs

Handheld Games

Portable Consumer Electronics

Features

S 28V Step-Up DC-DC Converter with Integrated

nMOS Power Switch

S Built-In 10-Bit PWM Control for Improved Efficiency
S No Discharge Path During PWM Off Period for

Increased Battery Life

S Fixed 2MHz Switching for Smaller Components

Drives up to 6 Series WLEDs

S ±8kV Human Body Model (HBM) ESD Protection

for GPIOs and Boost-Converter Output

S Five Open-Drain GPIOs Capable of Constant-

Current LED Drive with Individual 8-Bit PWM
Intensity Control

S 2.7V to 5V Power-Supply Operation
S 400kbps, 5.5V Tolerant I2C Interface
S Four I2C Slave Address Choices
S RST Input Clears Serial Interface and Exits

Shutdown (Reset-Run Option)

S Small (2.31mm x 2.31mm) WLP Package

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX6948BGWA+

-40NC to +105NC

25 WLP

+Denotes a lead(Pb)-free/RoHS-compliant package.

Typical Operating Circuit

2.7V TO 5.0V

2.2FF

0.1FF

47nF

10µH

1.7V TO V+

LX

V+

MAX6948B

SCL

SCL

SDA

SDA

RST

RST

V

DD

COMP

AD0

GND

OUT

PGND

LEDSW

0.22FF

R

B

FB

V

EXT

P0

P1

P2

P3

P4

B

G

R

MAX6948B

NOTE: RB = 0.2V/I

_______________________________________________________________ Maxim Integrated Products 1

= 0.2V/0.03A = 6.7I.

LED

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

High-Efficiency PWM LED Driver with Boost
Converter and Five Constant-Current GPIO Ports

ABSOLUTE MAXIMUM RATINGS

V+ to GND ...............................................................-0.3V to +6V

VDD, COMP to GND ....................................-0.3V to (V+ + 0.3V)

PGND to GND ......................................................-0.3V to +0.3V

LX to PGND (Note 1) .............................................-0.3V to +30V

Current into LX (Note 1) ...................................................700mA

OUT, LEDSW to PGND (Note 1) ...........................-0.3V to +30V

P0–P4 to GND .........................................................-0.3V to +6V

RST, SDA, SCL, AD0 to GND .................. -0.3V to (VDD + 0.3V)

FB to PGND (Note 1) ............................................-0.3V to +0.3V

MAX6948B

I.C. to GND ........................................................... -0.3V to +0.3V

DC Current on P0–P4 .........................................................50mA

DC Current on SDA ............................................................10mA

Total GND Current ............................................................150mA

Total PGND Current .........................................................150mA

Note 1: LX, FB, LEDSW pins have an internal clamp diode to PGND. Applications that forward bias these diodes should take care

not to exceed the power dissipation limits of the device.

Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a

single-layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-

tutorial.

Note 3: Refer to the Pb-free solder reflow requirement in J-STD -020, Rev D.1.

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.

Continuous Power Dissipation (TA = +70NC)

25-Bump WLP (derate 10.8mW/NC above +70NC) ......866mW

Junction-to-Ambient Thermal Resistance (BJA) (Note 2)

25-Bump WLP ..............................................................93NC/W

Operating Temperature Range
(T

to T

MIN

Junction Temperature .....................................................+150NC

Storage Temperature Range ............................ -65NC to +150NC

ESD Protection
Human Body Model (RD = 1.5kI, CS = 100pF)

P0–P4, OUT, LEDSW, FB to GND ................................Q8kV

All Other Pins ................................................................Q2kV

Lead Temperature (soldering, 10s)

25-Bump WLP ............................................................. (Note 3)

) .............................................. -40NC to +105NC

MAX

ELECTRICAL CHARACTERISTICS

(Typical Application Circuit, V+ = 2.7V to 5.0V, VDD = 1.7V to V+, TA = T
V+ = 3.3V, V

Operating Supply Voltage (V+) V+ 2.7 3.3 5.0 V
Operating Supply Voltage (VDD) V

Output Load External Supply
Voltage

Port External Supply Voltage V
Port Voltage (P0, P4) V
Power-On-Reset Voltage V

Standby Current I

Standby Current in Reset
(Interface Active)

= 2.5V, TA = +25NC.) (Note 4)

DD

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DD

V

OUT

EXT

PORT

POR

STBY

I

RST

Boost-converter output 28 V

P0–P4 at high impedance 5.5 V
Constant-current on V+ V
Voltage rising 1.7 V

Standby mode,
boost converter off,
RST = VDD, all digi-
tal inputs at VDD or
GND

Standby mode,
RST = GND,
f

= 400kHz, all

SCL

other digital inputs
at VDD or GND

to T

MIN

TA = +25NC 1.5 4

TA = T

TA = +25NC 1.6 4

TA = T

, unless otherwise noted. Typical values are at

MAX

1.7 2.5 V+ V

to T

MIN

MIN

to T

MAX

MAX

6

6

FA

FA

2

High-Efficiency PWM LED Driver with Boost

Converter and Five Constant-Current GPIO Ports

ELECTRICAL CHARACTERISTICS (continued)

(Typical Application Circuit, V+ = 2.7V to 5.0V, VDD = 1.7V to V+, TA = T
V+ = 3.3V, V

= 2.5V, TA = +25NC.) (Note 4)

DD

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MIN

to T

, unless otherwise noted. Typical values are at

MAX

MAX6948B

One port set to

Change in Supply Current per
30mA Port

Change in Supply Current per
10mA Port

GPIO PORTS (P0–P4)

Input High Voltage V

Input Low Voltage V

Input Leakage Current I
Input Capacitance 10 pF

30mA Port Sink Constant Current
(P0, P1)

10mA Port Sink Constant Current
(P2, P3, P4)

Logic Output Low Voltage V

DI

DD30

DI

DD10

IH1

IL1

IN

I

PORT30

I

PORT10

OL1

30mA constant cur­rent; all other ports
are digital inputs at
VDD or GND

One port set to 5mA
constant current
half-current setting;
all other ports are
digital inputs at VDD
or GND

Port I/O register value set to 0x01

Port I/O register value set to 0x01

Port I/O register
value set to 0x02,
V+ = 3.3V, V
V

LED

(Note 5)

5mA half-current
setting, port I/O
register value set
to 0x02, V+ = 3.3V,
V

- V

EXT

to 1.5V (Note 5)

I

SINK

0x00

EXT

= 0.5V to 1.5V

= 0.5V

LED

= 2mA, port I/O register value set to

TA = +25NC 3 6.2

TA = T

TA = +25NC 1.3 1.7

TA = T

TA = +25NC 27 30 34

-

TA = T

TA = +25NC 4.4 5 5.6

TA = T

MIN

MIN

MIN

MIN

to T

to T

to T

to T

MAX

MAX

MAX

MAX

(0.7 x

VDD)

25 35

3.7 6.3

mA

7

mA

2

(0.3 x

VDD)

±0.03 Q1 FA

mA

mA

0.17 0.3 V

V

V

30mA Port Sink Constant-Current
Matching (P0, P1)

10mA Port Sink Constant-Current
Matching (P2, P3, P4)

Constant-Current Slew Time

DI

PORT30

DI

PORT10

Constant current set
to 30mA, V+ = 3.3V,
TA = +25NC (Note 6)

Constant current set
to 5mA half-current
setting, V+ = 3.3V,
TA = +25NC (Note 6)

20% current to 80% current, port I/O regis­ter value changed from 0x01 to 0x02

V

= 1V Q0.7 Q5

PORT

V

= 2.75V Q5

PORT

V

= 1V Q2 Q5 %

PORT

%

2 Fs

3

High-Efficiency PWM LED Driver with Boost
Converter and Five Constant-Current GPIO Ports

ELECTRICAL CHARACTERISTICS (continued)

(Typical Application Circuit, V+ = 2.7V to 5.0V, VDD = 1.7V to V+, TA = T
V+ = 3.3V, V

BOOST CONVERTER

Undervoltage Lockout Threshold V

Undervoltage Lockout Threshold
Hysteresis

MAX6948B

Continuous Output Current I

Operating Current

LX Current Limit V+ = 3.3V, TA = +25°C 430 500 570 mA
LX Saturation Voltage ILX = 200mA 0.1 0.25 V
LX Leakage Current I
OUT Leakage Current I
Operating Frequency f

Minimum Duty Cycle

Maximum Duty Cycle 95 %
GM Amplifier Transconductance 250 FS
FB Leakage Current I

Feedback Output Voltage V

Quick-Start Charge Current I

Quick-Start Time

Shutdown Discharge Resistance R
Output Current Line Regulation 3.0V < V+ < 5.0V 2 %/V
Thermal Shutdown Threshold 150 NC
Thermal Shutdown Threshold

Hysteresis
Overvoltage Threshold V
Overvoltage Threshold

Hysteresis

SERIAL INTERFACE (SDA, SCL, AD0, RST)

Input High Voltage V

Input Low Voltage V

Input Leakage Current I
Output Low Voltage SDA V
Input Capacitance C

= 2.5V, TA = +25NC.) (Note 4)

DD

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

UVLO

V

HYS

WLED

LXOFF

OUTOFFVOUT

BOOST

FB

FB

QS

COMP

OV

V

OV_HYS

IH2

IL2

IN2

OL2

IN2

V+ rising 2.65
V+ falling 2.3

100% boost LED PWM, full-current setting,
RB = 6.67I, I

Run bit = 1, boost standby bit = 0, 0%
boost LED PWM

0% boost LED PWM, VLX = 10V 8 FA

= 28V, boost converter in shutdown 16 23 FA

Continuous conduction mode 10
Discontinuous conduction mode 0

VFB = 100mV ±0.01 Q1 FA

Half-current setting, V+ = 3.3V, TA = +25°C 94 100 106

Full-current setting, V+ = 3.3V, TA = +25°C 190 200 210
Half-current setting 90 100 110
Full-current setting 175 200 225

From enable command STOP condition to
output regulation, C
(Note 7)

V

Rising 28 29 30 V

OUT

I

= 6mA 0.3 V

SINK

WLED

= VFB/R

COMP

to T

MIN

B

= 0.047FF

, unless otherwise noted. Typical values are at

MAX

30 mV

30 mA

2 mA

2 MHz

150 FA

3.5 5 ms

20 kI

9 NC

4 V

0.7 x
V

DD

0.3 x
V

DD

0.03 FA

10 pF

V

%

mV

V

V

4

High-Efficiency PWM LED Driver with Boost

Converter and Five Constant-Current GPIO Ports

TIMING CHARACTERISTICS

(Typical Application Circuit, V+ = 2.7V to 5.0V, VDD = 1.7V to V+, TA = T
V+ = 3.3V, VDD = 2.5V, TA = +25NC.) (Note 4)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Internal Boost-Converter PWM
Clock Frequency

Internal GPIO PWM Clock
Frequency

SCL Serial-Clock Frequency f
Bus Free Time Between a STOP

and START Condition

Hold Time (Repeated) START
Condition

Repeated START Condition Setup
Time

STOP Condition Setup Time t
Data Hold Time t
Data Setup Time t
SCL Clock Low Period t
SCL Clock High Period t
Rise Time of Both SDA and SCL

Signals, Receiving

Fall Time of Both SDA and SCL
Signals, Receiving

Fall Time of SDA Transmitting t

Pulse Width of Spike Suppressed t
Serial Bus Timeout t
Capacitive Load for Each Bus

Line
RST Pulse Width

f

INT_

BOOST

f

INT_GPIO

SCL

t

BUF

t

HD, STA

t

SU, STA

SU, STO

HD, DAT

SU, DAT

LOW

HIGH

t

R

t

F

F, TX

SP

OUT

C

b

t

W

(Note 8) 0.9

(Notes 7, 9)

(Notes 7, 9)

(Notes 7, 9)

(Notes 7, 10) 50 ns

(Note 7) 400 pF

MIN

to T

, unless otherwise noted. Typical values are at

MAX

98 125 145 kHz

24 31.25 38 kHz

400 kHz

1.3

0.6

0.6

0.6

180 ns

1.3

0.7
20 +

0.1C

20 +

0.1C

20 +

0.1C

20 30 50 ms

1

b

b

b

300 ns

300 ns

250 ns

Fs

Fs

Fs

Fs
Fs

Fs
Fs

Fs

MAX6948B

Note 4: All parameters are tested at TA = +25NC. Specifications over temperature are guaranteed by design.
Note 5: The DI
Note 6: Current matching is defined as the percent error of any individual port from the average current of the maximum value

measured and the minimum value measured. It can be found using the equation DI
I

Note 7: Guaranteed by design.
Note 8: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) to

Note 9: I
Note 10: Input filters on the SDA, SCL, and AD0 inputs suppress noise spikes less than 50ns.

MMAVG

bridge the undefined region of SCL’s falling edge.

SINK

specifies current matching between ports of a single part.

PORT_

= 100 x (I

where I

P 6mA. Cb = total capacitance of one bus line in pF. tR and tF are measured between 0.3 x V

MMAVG

= (I

MEASMAX

+ I

MEASMIN

)/2.

PORT_

- I

MMAVG

and 0.7 x VDD.

DD

MEAS

)/

5

High-Efficiency PWM LED Driver with Boost

MAX6948B toc08

5.00

Converter and Five Constant-Current GPIO Ports

Typical Operating Characteristics

(V+ = 3.3V, VDD = 2.5V, TA = +25NC, unless otherwise noted.)

90

FULL-CURRENT

3 LEDs

85

MAX6948B

80

75

EFFICIENCY (%)

70

65

60

2.70 5.25

FULL-CURRENT 5 LEDs

HALF-CURRENT

3 LEDs

HALF-CURRENT

5 LEDs

V+ (V)

SOFT-START V+, V

500mV/div

V+

5V/div

V

OUT

EFFICIENCY vs. V+

FULL-CURRENT

HALF-CURRENT

(512/1024)

OUT

7 LEDs

7 LEDs

4.744.233.723.21

MAX6948B toc04

500mV/div

MAX6948B toc01

500mV/div

5V/div

V

OUT

10V/div

GND

5V/div

V

OUT

V+

LX

V+

SWITCHING WAVEFORMS

SOFT-START V+, V

(1024/1024)

OUT

MAX6948B toc02

MAX6948B toc05

500mV/div

5V/div

V

OUT

SOFT-START V+, V

V+

SHUTDOWN RESPONSE (V+, V

(10/1024)

OUT

MAX6948B toc03

OUT)

MAX6948B toc06

500mV/div
V+

5V/div
V

OUT

GND

(mA)

WLED

I

I

30mA OUTPUT CURRENT vs. V+

WLED

35

MAX6948B toc07

25

15

5

FULL-CURRENT 6 LEDs

HALF-CURRENT 6 LEDs

V+ (V)

V+ (V)

STANDBY CURRENT (µA)

4.544.083.623.162.70 5.00

STANDBY CURRENT I

4

3

2

1

0

+25NC

-40NC

V+ (V)

+105NC

RST

vs. V+

+85NC

4.544.083.623.162.70

STANDBY CURRENT I

5.8

5.7

5.6

5.5

5.4

STANDBY CURRENT (mA)

5.3

5.2

STBY

+25NC, +85NC, +105NC

V+ (V)

vs. V+

-40NC

MAX6948B toc09

4.544.083.623.162.70 5.00

6

High-Efficiency PWM LED Driver with Boost

V+ (V)

Converter and Five Constant-Current GPIO Ports

Typical Operating Characteristics (continued)

(V+ = 3.3V, VDD = 2.5V, TA = +25NC, unless otherwise noted.)

MAX6948B

SUPPLY CURRENT vs. V+

(BOOST ON, 10% PWM,

FULL CURRENT AND HALF CURRENT)

6.0
TA = -40NC, +25NC, +85NC, +105NC

5.9

5.8

5.7

5.6

SUPPLY CURRENT (mA)

5.5

5.4

DELTA SUPPLY CURRENT P0 vs. V+

(DIFFERENCE IN CURRENT FROM

PORT OFF TO ON)

5.70

5.65

5.60

5.55

5.50

5.45

5.40

DELTA SUPPLY CURRENT P0 (mA)

5.35

5.30

+25NC, +85NC, +105NC

4.544.083.623.162.70 5.00

-40NC

4.544.083.623.162.70 5.00

SUPPLY CURRENT vs. V+

(BOOST ON, 50% PWM,

FULL CURRENT AND HALF CURRENT)

6.5
TA = -40NC, +25NC, +85NC, +105NC

6.4

MAX6948B toc10

6.3

6.2

6.1

6.0

SUPPLY CURRENT (mA)

5.9

5.8

5.7

DELTA SUPPLY CURRENT P2 vs. V+

(DIFFERENCE IN CURRENT

FROM PORT OFF TO ON)

5.70

5.65

MAX6948B toc13

5.60

5.55

5.50

5.45

5.40

DELTA SUPPLY CURRENT P2 (mA)

5.35

5.30

4.544.083.623.162.70 5.00

-40NC

+25NC, +85NC, +105NC

4.544.083.623.162.70 5.00

V+ (V)

FULL CURRENT AND HALF CURRENT)

7.2
TA = -40NC, +25NC, +85NC, +105NC

7.1

7.0

MAX6948B toc11

6.9

6.8

6.7

6.6

6.5

SUPPLY CURRENT (mA)

6.4

6.3

6.2

40

MAX6948B toc14

OUTPUT SINKING CURRENT (mA)

FULL-CURRENT PO

30

20

FULL-CURRENT P2

10

0

0 5

SUPPLY CURRENT vs. V+

(BOOST ON, 10% PWM,

4.544.083.623.162.70 5.00

OUTPUT SINKING CURRENT

vs. V

PORT

V+ = 5V

HALF-CURRENT PO

HALF-CURRENT P2

V

(V)

PORT

MAX6948B toc12

MAX6948B toc15

4321

OUTPUT SINKING CURRENT

vs. V

V

PORT

PORT

(V)

40

FULL-CURRENT PO

30

20

10

OUTPUT SINKING CURRENT (mA)

0

HALF-CURRENT PO

FULL-CURRENT P2

HALF-CURRENT P2

0 1.0

V+ = 5V

0.80.60.40.2

MAX6948B toc16

BOOST

STAGGER PWM PORT WAVEFORMS

vs. TIME ALL (50% PWM)

P0

P2

P3

P1

P4

1ms/div

MAX6948B toc17

7

High-Efficiency PWM LED Driver with Boost
Converter and Five Constant-Current GPIO Ports

Pin Configuration

TOP VIEW

(BUMP IN BOTTOM)

MAX6948B

SCL SDA V+

AD0 V+ V+

WLP

MAX6948B

P0

A1

P1

B1 B2 B3 B4 B5

P2

C1 C2 C3 C4 C5

P3

D1 D2 D3 D4 D5

P4

E1 E2 E3 E4 E5

RST

A2 A3 A4 A5

V

DD

GND N.C. I.C. COMP

GND FB PGND PGND

OUT LEDSW LX LX

(2.31mm x 2.31mm)

Pin Description

PIN NAME FUNCTION

A1 P0 GPIO Port. Open-drain I/O. P0 can be configured as a 30mA (max) constant sink current output.
A2

RST

A3 SCL I2C-Compatible, Serial-Clock Input
A4 SDA I2C-Compatible, Serial-Data I/O

A5, B4, B5 V+

B1 P1 GPIO Port. Open-drain I/O. P1 can be configured as a 30mA (max) constant sink current output.
B2 V

DD

B3 AD0 Address Input. AD0 selects up to four device slave addresses (Table 13).
C1 P2 GPIO Port. Open-drain I/O. P2 can be configured as a 10mA (max) constant sink current output.

C2, D2 GND Ground. Connect to PGND.

C3 N.C. No Connection. Internally not connected.
C4 I.C. Internally Connected. Connect I.C. to GND for normal operation.

C5 COMP

D1 P3 GPIO Port. Open-drain I/O. P3 can be configured as a 10mA maximum constant sink current output.

D3 FB

D4, D5 PGND Power Ground. Connect PGND to GND.

E1 P4 GPIO Port. Open-drain I/O. P4 can be configured as a 10mA (max) constant sink current output.
E2 OUT Output Voltage Sense Input for Boost Converter
E3 LEDSW High-Voltage, Constant-Current Input. Connect LEDSW to the cathode-end of the WLED string.

E4, E5 LX Inductor Switch Node

Active-Low Reset Input

Boost-Converter Supply Voltage and Positive Supply Voltage. Bypass V+ to GND with a 2.2FF or
higher value ceramic capacitor.

I2C Logic Supply Voltage. Bypass VDD to GND with a 0.1FF or higher value ceramic capacitor.

Compensation Terminal for the Boost Converter. A capacitor from COMP to PGND determines the
boost-converter stability.

Load Current-Sense Voltage Feedback for the Boost Converter. A resistor between FB and PGND
sets the maximum load current.

8

High-Efficiency PWM LED Driver with Boost

Converter and Five Constant-Current GPIO Ports

Functional Block Diagram

LX

LX

OUT

V

PWM AND

MAX6948B

V+

UVLO

OVP

DD

THERMAL

SHUTDOWN

GATE DRIVE

n-CHANNEL
MOSFET

n-CHANNEL
MOSFET

PGND

PGND

COMP

LEDSW

FB

MAX6948B

RST

SDA
SCL
ADO

POR

I2C

INTERFACE

125kHz, 31.25kHz

OSCILLATOR

CONTROL

REGISTERS

Detailed Description

The MAX6948B general-purpose input/output (GPIO)
peripheral with integrated boost converter provides a
boost converter capable of driving 6 WLEDs and five I/O
ports capable of driving LEDs powered from an alternate
power supply such as the Li+ battery. The integrated
2MHz boost converter minimizes the size and cost of
external components and supplies 30mA of load current
at up to 28V. The feedback input to the error amplifier
has a typical set point of 0.1V to minimize power dis­sipation. External compensation keeps the converter
stable under all load conditions from 5V up to 28V. The
MAX6948B includes overvoltage and open-circuit detec­tion to prevent damage to the IC.

An I2C-programmable 10-bit PWM signal enables 1024
levels of WLED intensity. During PWM off-time, the
internal switch at the LEDSW pin disconnects the series
WLEDs. This limits the PWM off-time leakage current to
a minimum, limited only by the PWM switch internal to
the MAX6948B. Consequently, the boost output voltage

BANDGAP

REFERENCE

PWM AND

GPIO LOGIC

LED ENABLE

GPIO ENABLE

GPIO INPUT

CURRENT

DAC

PORT GPIO

AND

CONSTANT-

CURRENT

LED DRIVE

P0

P1

P2

P3

P4

remains almost constant during PWM on-/off-time peri­ods. This new approach provides advantages of minimal
WLED color change for sharp WLED on and off, and
more power efficiency due to minimal leakage.

The five GPIO ports function as logic inputs, open­drain logic outputs, or constant-current sinks in any
combination. Ports withstand 5.5V independent of the
MAX6948B’s supply voltage. Two of the ports drive
additional LEDs up to 30mA, while the other three ports
drive LEDs at up to 10mA/port. The MAX6948B features
shutdown and standby modes for low-power dissipa­tion. The constant-current drivers contain programmable
PWM outputs and allow staggering to reduce the input
peak current requirements. The I/O ports also feature
ramp-up and ramp-down controls.

The MAX6948B features a single input to select from four
I2C slave addresses. Programming and functionality for
the five GPIO ports is identical to the MAX6946/MAX6947
I/O expanders.

9