MAX6946CAWE+T ,10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity ControlApplicationsOrdering InformationCellular Phones LCD BacklightsPKGPART PIN-PACKAGEPortable Equipment ..
MAX694CPA ,Microprocessor Supervisory CircuitsELECTRICAL CHARACTERISTICS
(Vcc = full operating range, VBATT = 2.8V, T, = 25°C, unless otherwis ..
MAX694CPA ,Microprocessor Supervisory CircuitsApplications
Computers
Controllers
Intelligent Instruments
Automotive Systems
Critical ..
MAX694CPA ,Microprocessor Supervisory CircuitsFeatures
. Precision Voltage Monitor
4.65V in MAX690, MAX691, MAX694 and MAX695
4.40V in MAX69 ..
MAX694CPA+ ,Microprocessor Supervisory CircuitsElectrical CharacteristicsV = full operating range, V = 2.8V, T = +25°C, unless otherwise noted.)CC ..
MAX694EPA ,Microprocessor Supervisory CircuitsApplications
Computers
Controllers
Intelligent Instruments
Automotive Systems
Critical ..
MB39A106 , 2-Channel DC/DC Converter IC with Overcurrent Protection Symmetrical-Phase Type
MB39A108 ,5-Channel DC/DC Converter IC with Synchronous Rectificationfeatures make MB39A108 optimal for power supplies inhigh-performance portable devices such as digit ..
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB40166 ,AD/DA CONVERTERFUJITSU SEMICONDUCTORDS04-28500-5EDATA SHEETASSPAD/DA CONVERTERMB40166/MB401761-CHANNEL 6-BIT AD/DA ..
MAX6946CAWE+T
10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control
General DescriptionThe MAX6946/MAX6947 I2C-/SMBusTM-compatible,
serial-interfaced peripherals provide microprocessors
with 10 I/O ports rated to 7V.
Each port can be configured as a 2.5mA to 20mA con-
stant-current LED driver (static or PWM), a 1.25mA to
10mA constant-current LED driver (static or PWM), an
open-drain logic output, or an overvoltage-protected
Schmitt logic input.
Analog and switching LED intensity control includes indi-
vidual 8-bit PWM control per output, individual 1-bit ana-
log current control (half/full scale) per output, and a global
3-bit DAC current control that applies to all LED outputs.
The MAX6946/MAX6947 can stagger the PWM timing of
the 10-port outputs in consecutively phased 45°incre-
ments. Staggering the outputs spreads the PWM load
currents over time in eight steps, helping to even out
the power-supply current and reduce the RMS current.
For a similar part with an SPITM-/QSPITM-/ or MICROWIRETM-
compatible interface, refer to the MAX6966/MAX6967
data sheet.
Applications
Features2.25V to 3.6V OperationI/O Ports Default to High Impedance (LEDs Off)
on Power-UpI/O Port Inputs Are Overvoltage Protected to 7VI/O Port Outputs Are 7V-Rated Open-Drain, 10mAor 20mA Constant-Current Static/PWM LED
Drivers, or Open-Drain Logic OutputsI/O Ports Support Hot InsertionIndividual 8-Bit PWM Intensity Control for Each LEDRST
Input Clears Serial Interface and Can Exit
Shutdown (Warm Start)MAX6946 OSC Input Allows for External PWMClock InputMAX6947 AD0 Input Selects from Two Slave
AddressesAuto Ramp-Up Out of Shutdown, and Up to 4sHold-Off Before Ramp-Down into Shutdown0.8µA (typ) Shutdown Current-40°C to +125°C Temperature RangeTiny WLP Package (4 x 4 Grid)
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
Ordering InformationMAX6946
MAX6947
VDD
+3.3V
SDA
VEXT = +5V
SCL
SDA
SCL
GND
OSC*LOGIC INPUT
LOGIC INPUT
LOGIC INPUT
LOGIC INPUT
LOGIC INPUT
LOGIC INPUT
LOGIC INPUT
RST
AD0**
*MAX6946 ONLY.
**MAX6947 ONLY.
ypical Operating Circuit19-0598; Rev 3; 2/08
+Denotes a lead-free package.
*EP = Exposed pad.
Note:All devices are specified over the -40°C to +125°C operating
temperature range..
EVALUATION KIT
AVAILABLE
PARTPIN-PACKAGEPKG
CODE
MAX6946ATE+16 TQFN-EP*T1633-4
MAX6946CAWE+16 WLPW162B2-1
MAX6947ATE+16 TQFN-EP*T1633-4
SMBus is a trademark of Intel Corp.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Cellular Phones
Portable Equipment
RGB LED Drivers
LCD Backlights
Keypad Backlights
LED Status Indicators
(BUMPS ON BOTTOM)
16-BUMP, 2.1mm x 2.1mm WLPVDDSDARSTSCL
OSCP0P9P1P2P8P3P4P6GND
TOP VIEWA2A3A4B3B2B1C2C3C4D2D3D4
MAX6946C
Pin ConfigurationsPin Configurations continued at end of data sheet.
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= 2.25V to 3.6V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VDD= 3.3V, TA= +25°C.) (Note 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.
VDD to GND.............................................................-0.3V to +4V
SCL, SDA, AD0, RST, OSC to GND.........................-0.3V to +6V
P0 to P9 to GND.......................................................-0.3V to +8V
DC Current into P0 to P9....................................................24mA
DC Current into SDA...........................................................10mA
RSTSink Current.................................................................10mA
Total GND Current............................................................280mA
Continuous Power Dissipation (TA= +70°C)
16-Pin TQFN (derate 14.7mW/°C over +70°C)..........1176mW
16-Bump WLP (derate 13.3mW/°C over +70°C)........1066mW
Operating Temperature Range (TMIN, TMAX)....-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOperating Supply VoltageVDD2.253.60V
Output Load External Supply
Voltage P0–P9VEXT7V
Power-On-Reset VoltageVPORVDD rising1.91V
16-pin TQFN128Power-On-Reset Voltage HysteresisPORHYS16-bump WLP33mV
TA = +25°C1.01.3
TA = TMIN to +85°C1.3
Standby Current Interface Idle
(PWM Disabled, All Ports High
Impedance)
ISTBY
RST at VDD;
fSCL = 0Hz; other digital
inputs at VDD or GNDTA = TMIN to TMAX1.5
TA = +25°C1723
TA = TMIN to +85°C24
Standby Current in Reset
(PWM Disabled, All Ports High
Impedance)
IRST
RST at GND; fSCL =
400kHz; other digital
inputs at VDD or GNDTA = TMIN to TMAX25
TA = +25°C5060
TA = TMIN to +85°C62
Supply Current Interface Active
(Reset Run Enabled, PWM
Disabled, All Ports High
Impedance)
IDD
fSCL = 400kHz; other
digital inputs at VDD or
GNDTA = TMIN to TMAX65
TA = +25°C1.581.8
TA = TMIN to +85°C1.9ΔIDD10
One port set to 10mA
constant current; all other
ports' output registers set
to 0x00, 0x01, or 0xFF;
digital inputs at VDD or
GNDTA = TMIN to TMAX2.0
TA = +25°C3.23.6
TA = TMIN to +85°C3.8
Delta Supply Current Interface Idle
ΔIDD20
One port set to 20mA
constant current; all other
ports' output registers set
to 0x00, 0x01, or 0xFF;
digital inputs at VDD or
GNDTA = TMIN to TMAX4.0
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
ELECTRICAL CHARACTERISTICS (continued)(VDD= 2.25V to 3.6V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VDD= 3.3V, TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput High Voltage
(P0–P9, SDA, SCL, RST, AD0, OSC)VIHP0–P9: output register set to 0x010.7
x VDDV
Input Low Voltage
(P0–P9, SDA, SCL, RST, AD0, OSC)VILP0–P9: output register set to 0x010.3
x VDDV
Input Leakage Current
(P0–P9, SDA, SCL, RST, AD0, OSC)IIH, IIL-0.2+0.2µA
Input Capacitance
(P0–P9, SDA, SCL, RST, AD0, OSC)10pF
TA = +25°C9.31010.5
TA = TMIN to +85°C
16-pin TQFN9.111.010mA Port Nominal Sink Constant
Current (P0–P9)IOUT
Outp ut r eg i ster set to 0x02,D D = 3.3V ,E X T - V LE D = 1V ( N ote 3) TA = TMIN to +85°C
16-bump WLP9.011.0
TA = +25°C19.002021.12
TA = TMIN to +85°C
16-pin TQFN18.621.820mA Port Nominal Sink Constant
Current (P0–P9)IOUT
Outp ut r eg i ster set to 0x02,D D = 3.3V ,E X T - V LE D = 1V ( N ote 3) TA = TMIN to +85°C
16-bump WLP18.422.0
TA = +25°C, VDD = 3.3V, VP0 to VP9 = 1.4V,
IOUT = 20mA±2.0±4.0
Port Sink Constant-Current
MatchingΔIOUT
TA = +25°C, VDD = 3.3V, VP0 to VP9 = 1.4V,
IOUT = 10mA±2.0±5.0
Port Logic Output Low Voltage
(P0–P9)VOLP_Output register set to 0x00,
ISINK = 0.5mA0.5V
Port Logic Output Low
Short-Circuit Current (P0–P9)
Output register set to 0x00,
VOLP_ = 5V10mA
Port Slew TimeFrom 20% current to 80% current2µs
Output Low Voltage
(SDA)VOLSDAISINK = 6mA300mV
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
TIMING CHARACTERISTICS (Figure 8)(VDD= 2.25V to 3.6V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VDD= 3.3V, TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS16-pin TQFN233242Internal PWM Clock FrequencyfINT16-bump WLP203245kHz
External PWM Clock FrequencyfOSC100kHz
Serial-Clock FrequencyfSCL400kHz
Bus Free Time Between a STOP and
a START ConditiontBUF1.3µs
Hold Time, (Repeated) START
ConditiontHD, STA0.6µs
Repeated START Condition Setup
TimetSU, STA0.6µs
STOP Condition Setup TimetSU, STO0.6µs
Data Hold TimetHD, DAT(Note 3)0.9µs
Data Setup TimetSU, DAT180ns
SCL Clock Low PeriodtLOW1.3µs
SCL Clock High PeriodtHIGH0.7µs
Rise Time of Both SDA and SCL
Signals, ReceivingtR(Notes 4, 5)20
+ 0.1Cb300ns
Fall Time of Both SDA and SCL
Signals, ReceivingtF(Notes 4, 5)20
+ 0.1Cb300ns
Fall Time of SDA TransmittingtF, TX(Notes 4, 6)20
+ 0.1Cb250ns
Pulse Width of Spike SupressedtSP(Note 7)50ns
Capacitive Load for Each Bus LineCb(Note 4)400pF
RST Pulse WidthtW0.1µs
16-pin TQFN3.0RST Rising Edge to
MAX6946/MAX6947 ACK to Cancel
Reset Run
tRSTRUN
Reset Run enabled,
internal oscillator
enabled16-bump WLP2.5
RST Rising Edge to
MAX6946/MAX6947 ACK to Ensure
Reset Run
tRSTRUNReset Run enabled, internal oscillator
enabled5.6ms
Note 1:All parameters are tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2:Port current is factory trimmed to meet a median sink current of 20mA and 10mA over all ports. The ΔIOUTspecification
guarantees current matching between parts.
Note 3:A master device must provide a hold time of at least 300ns for the SDA signal (referred to VILof the SCL signal) in order to
bridge the undefined region of SCL’s falling edge.
Note 4:Not production tested. Guaranteed by design.
Note 5:Cb= total capacitance of one bus line in picoFarads; tRand tFare measured between 0.3 x VDDand 0.7 x VDD.
Note 6:ISINK≤6mA.
Note 7:Guaranteed by design. Input filters on the SDA and SCL inputs suppress noise spikes of less than 50ns.
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
STANDBY CURRENT (ISTBY)
vs. TEMPERATURE TEMPERATURE (°C)
STANDBY CURRENT (
A)
MAX6946/47 toc01
VDD = 3.6V
VDD = 3.3V
VDD = 2.7V
VDD = 2.25V
SUPPLY CURRENT (IDD)
vs. TEMPERATURETEMPERATURE (°C)
SUPPLY CURRENT (
MAX6946/47 toc02
VDD = 2.25V
VDD = 2.7V
VDD = 3.3VVDD = 3.6V
STANDBY CURRENT (IRST)
vs. TEMPERATURE TEMPERATURE (°C)
STANDBY CURRENT (
A)
MAX6946/47 toc03
VDD = 2.7V
VDD = 3.6V
VDD = 3.3V
VDD = 2.25V
DELTA SUPPLY CURRENT (IDD20)
vs. TEMPERATURE TEMPERATURE (°C)
DELTA SUPPLY CURRENT (mA)
MAX6946/47 toc04
VDD = 3.6VVDD = 3.3V
VDD = 2.7VVDD = 2.25V
DELTA SUPPLY CURRENT (IDD20)
vs. TEMPERATURE TEMPERATURE (°C)
DELTA SUPPLY CURRENT (mA)
MAX6946/47 toc05
VDD = 3.6V
VDD = 3.3V
VDD = 2.7V
VDD = 2.25V
OUTPUT SINKING CURRENT
vs. VEXT - VLED AT 10mAVEXT - VLED (V)
OUTPUT SINKING CURRENT (mA)
MAX6946/47 toc06
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
OUTPUT SINKING CURRENT
vs. VEXT - VLED AT 20mAVEXT - VLED (V)
OUTPUT SINKING CURRENT (mA)
MAX6946/47 toc07
STAGGER PWM PORT WAVEFORMS
(OUTPUT REGISTERS SET TO 0x80)
MAX6946/47 toc08
1ms/div
PORT P0
2V/div
PORT P4
2V/div
PORT P7
2V/div
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
Pin Description
PINMAX6946/
MAX6947MAX6946C
NAMEFUNCTION1B4P0
2B3P1
3C4P2
4C3P3
5D4P4
I/O Ports. Configure P0–P4 as open-drain current sink outputs rated at
20mA (max), as CMOS-logic inputs, or as open-drain logic outputs.
Connect loads to a supply voltage no higher than 7V.D3GNDGround
7D2P5
8D1P6
9C2P7C1P8B1P9
I/O Ports. Configure P5–P9 as open-drain current sink outputs rated at
20mA (max), as CMOS-logic inputs, or as open-drain logic outputs.
Connect loads to a supply voltage no higher than 7V.
OSC (MAX6946)External Oscillator Input12B2AD0 (MAX6947)Address Input. Sets the device slave address (see Table 10).A1RSTActive-Low Reset InputA2VDDP osi ti ve S up p l y V ol tag e. Byp ass V D D to GN D w i th a 0.1µF cer am i c cap aci tor .A3SCLI2C-Compatible, Serial-Clock InputA4SDAI2C-Compatible, Serial-Data I/OEPExposed Pad on Package Underside. Connect to GND. Do not use as the
main ground connection.
CURRENT REFERENCE
INTERNAL
OSCILLATORI/O PORTS
RAMP-UP/RAMP-DOWN
CONTROLS
PWM CONTROLLER
EXTERNAL CLOCK INPUT*
CONFIGURATION
REGISTERI/O REGISTER
2-WIRE SERIAL INTERFACE
ADO**
RST**MAX6946 ONLY.
**MAX6947 ONLY.
SDA
SCL
OSC*
MAX6946
MAX6947
Block Diagram
Detailed DescriptionThe MAX6946/MAX6947 general-purpose input/output
(GPIO) peripherals provide 10 I/O ports, P0 to P9, con-
trolled through an I2C-compatible serial interface. Use
the 10 I/O ports as logic inputs, open-drain logic out-
puts, or constant-current sinks in any combination.
Ports withstand 7V independent of the MAX6946/
MAX6947s’ supply voltage whether used as logic
inputs, logic outputs, or constant-current sinks.
The MAX6946/MAX6947 feature shutdown and standby
modes for low-power dissipation. The I/O ports feature
pulse-width modulation (PWM) of the outputs and can
stagger the PWM timing of the 10 port outputs in con-
secutively phased 45°increments. The I/O ports also
feature ramp-up and ramp-down controls.
The MAX6946/MAX6947 feature a RSTinput to halt any
serial-interface transmission and bring the device out of
shutdown.
Open-drain logic outputs require external pullup resis-
tors to provide the logic-high reference. Ports config-
ured as open-drain logic outputs have a relatively weak
sink capability, but are still adequate for normal logic-
level outputs. The weak drive means that the short-cir-
cuit current is low enough that inadvertently driving an
LED from a port configured as a logic output is unlikely
to damage the LED.
The MAX6946 features a fixed I2C slave address of
010 0000 and provides an OSC input to accept an
external PWM clock input as an alternative to the inter-
nal PWM clock.
The MAX6947 features an AD0 input that uses two-level
logic to select from two I2C slave addresses. The
MAX6947 always uses the internal PWM clock.
Register StructureThe MAX6946/MAX6947 contain 22 internal registers
(see Table 1). Use registers 0x00 to 0x09 to individually
control ports P0 to P9. Registers 0x0A to 0x0D allow
more than one port control register to be written with
the same data to simplify software. Registers 0x0E and
0x0F do not store data, but return the port input status
when read. Registers 0x10 to 0x15 configure and con-
trol the device operation.
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
Table 1. Register Address Map
DESCRIPTION
ADDRESS
CODE
(HEX)
AUTO-
INCREMENT
ADDRESSPort P0 output level or PWM0x000x01
Port P1 output level or PWM0x010x02
Port P2 output level or PWM0x020x03
Port P3 output level or PWM0x030x04
Port P4 output level or PWM0x040x05
Port P5 output level or PWM0x050x06
Port P6 output level or PWM0x060x07
Port P7 output level or PWM0x070x08
Port P8 output level or PWM0x080x09
Port P9 output level or PWM0x090x10
Write ports P0–P9 with same
output level or PWM
Read port P0 output level or PWM
0x0A0x10
Write ports P0–P3 with same
output level or PWM
Read port P0 output level or PWM
0x0B0x10
Write ports P4–P7 with same
output level or PWM
Read port P4 output level or PWM
0x0C0x10
Write ports P8 or P9 with same
output level or PWM
Read port P8 output level or PWM
0x0D0x10
Read ports P7–P0 inputs0x0E0x0F
Read p or ts P 9 and P 8 i np uts0x0F0x0E
Configuration0x100x11
Ramp-down0x110x12
Ramp-up0x120x13
Output current ISET700x130x14
Output current ISET980x140x15
Global current0x150x10
Factory reserved; do not write to
this register0x7D—
MAX6946/MAX6947
Configuration Register (0x10)Use the configuration register to select PWM phasing
between outputs, test fade status, enable hardware
startup from shutdown, and select shutdown or run
mode (Table 2).
Initial Power-UpAll control registers reset upon power-up (Table 3).
Power-up status sets I/O ports P0 to P9 to high imped-
ance, and puts the device into shutdown. The
MAX6946/MAX6947 powers up in shutdown.
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
Table2. Configuration Register (0x10)
REGISTER BITDESCRIPTIONVALUEFUNCTIONInternal oscillator enabled as PWM clock sourceD7OSC enable*1External oscillator input enabled as PWM clock sourceRST does not change register dataD6RSTPOR options1RST resets registers to POR (power-on reset) statePWM outputs are in phaseD5PWM stagger1PWM outputs stagger phaseDevice not in hold-offD4Hold-off status**1Device in hold-offDevice not in fade-offD3Fade-off status**1Device in fade-offDevice not in ramp-upD2Ramp-up status**1Device in ramp-upReset Run disabledD1RST RUN enable1Reset Run enabledShutdown modeD0RUN enable1Run mode
*The OSCEN bit applies only to the MAX6946. OSCEN is always 0 for the MAX6947, and the MAX6947 ignores writes to the OSCEN bit.
**Read-only bits.
Table3. Initial Power-Up Register Status
REGISTER BITDESCRIPTIONPOWER-UP CONDITIONADDRESS
CODE (HEX)D7D6D5D4D3D2D1D0Port P0–P9 output level
or PWMPort 0–9 high impedance0x00–0x0911111111
ConfigurationS hutd ow n m od e, Reset Run d i sab l ed 0x100/1*0000000
Ramp-down/hold-offFade/hold-off disabled0x1100000000
Ramp-upDisabled0x1200000000
Output current ISET70IPEAK = 10mA for ports P7–P00x1300000000
Output current ISET98IPEAK = 10mA for ports P9, P80x1400000000
Global currentFull current0x1500000111
*Value is 0 for MAX6947 and 1 for MAX6946 bit.
I/O PortsThe MAX6946/MAX6947 contain 10 I/O ports.
Configure the 10 I/O ports as logic inputs, open-drain
logic outputs, or constant-current sinks in any combina-
tion. Table 4 shows a detailed description of the indi-
vidual port configuration registers 0x00 through 0x09.
Use registers 0x00–0x09 to individually assign each
port as a logic input, open-drain logic output or con-
stant-current sink (see the PWM Intensity Control and
Phasingsection). The I/O ports are high impedance
without VDDapplied and remain high impedance upon
power-up.
Figure 1 shows the I/O port structure of the MAX6946/
MAX6947. I/O ports P0 to P9 default to high impedance
on power-up, so LEDs or other port loads connected
draw no current. Ports used as inputs do not load their
source signals.
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control8-BIT LATCH
OUTPUT PORT
REGISTER
PWM
GENERATOR
1-BIT LATCH
OUTPUT CURRENT
REGISTER
4-BIT DAC
3-BIT LATCH
GLOBAL CURRENT
REGISTER
READ I/O
PORT COMMAND
TO/FROM
SERIAL
INTERFACE
MSB
ENABLE
I/O PORT
ENABLE = 0x00
SET
CURRENT
POSITION A: 0x00–0x01
POSITION B: 0x02–0xFF
CLOSE SWITCH: 0x02–0xFE
Figure1. Simplified Schematic of I/O Ports
Table4. Individual Port Configuration Options (Port Output Registers 0x00–0x09)
PORT TYPE
OUTPUT
REGISTER
CODE
RUN MODE (CONFIGURATION
REGISTER BIT D0 = 1)
SHUTDOWN
(CONFIGURATION REGISTER
BIT D0 = 0)
APPLICATION NOTESLow-logic
output0x00Logic-low output, not constant current
High-logic
output
Logic-high output with external pullup resistor;
otherwise, high impedance
Logic input
0x01
CMOS logic input
Lowest supply current,
unaffected by shutdown
Constant-
current static
sink output
0x02Static constant-current sink
output
Full constant-current drive
with no PWM
Constant-
current PWM
output
0x03–0xFE0x03 = 3/256 PWM duty cycle
0xFE = 254/256 PWM duty cycle
High impedance
Adjustable constant current
LED off0xFFLogic-high output with external pullup resistor; otherwise,
high impedanceLED off
MAX6946/MAX6947
Ports Configured as OutputsThe global-current register sets the full (maximum) con-
stant-current sink into an I/O port configured as an out-
put (Table 5). Each output port’s individual constant-
current sink can set to either half or full scale of the
global current by the output-current registers (Table 6).
By default, maximum current is 20mA, hence the default
maximum half current is 10mA.
Set each output port’s individual constant-current sink
to either half scale or full scale of the global current.
Use the output-current registers to set the individual
currents (Table 6). Set the global current by the global-
current register (Table 5).
Set each output current individually to best suit the
maximum operating current of an LED load, or even
adjust on the fly to double the effective intensity control
range of each output. The individual current selection is
10mA (half) or 20mA (full) when setting the global-cur-
rent register to its maximum value.
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
Table5. Global-Current Register Format (0x15)
REGISTER BITDESCRIPTIOND7D6D5D4D3D2D1D0Full current is 2.5mA; half current is 1.25mAXXXXX000
Full current is 5mA; half current is 2.5mAXXXXX001
Full current is 7.5mA; half current is 3.75mAXXXXX010
Full current is 10mA; half current is 5mAXXXXX011
Full current is 12.5mA; half current is 6.25mAXXXXX100
Full current is 15mA; half current is 7.5mAXXXXX101
Full current is 17.5mA; half current is 8.75mAXXXXX110
Full current is 20mA; half current is 10mAXXXXX111
Table6. Output-Current Register Format
REGISTER BITDESCRIPTIONADDRESS
CODE (HEX)D7D6D5D4D3D2D1D0Output P0 is set to half constant currentXXXXXXX0
Output P0 is set to full constant currentXXXXXXX1
Output P1 is set to half constant currentXXXXXX0X
Output P1 is set to full constant currentXXXXXX1X
Output P2 is set to half constant currentXXXXX0XX
Output P2 is set to full constant currentXXXXX1XX
Output P3 is set to half constant currentXXXX0XXX
Output P3 is set to full constant currentXXXX1XXX
Output P4 is set to half constant currentXXX0XXXX
Output P4 is set to full constant currentXXX1XXXX
Output P5 is set to half constant currentXX0XXXXX
Output P5 is set to full constant currentXX1XXXXX
Output P6 is set to half constant currentX0XXXXXX
Output P6 is set to full constant currentX1XXXXXX
Output P7 is set to half constant current0XXXXXXX
Output P7 is set to full constant current
0x13XXXXXXX
Output P8 is set to half constant currentXXXXXXX0
Output P8 is set to full constant currentXXXXXXX1
Output P9 is set to half constant currentXXXXXX0X
Output P9 is set to full constant current
0x14XXXX1X
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
PWM Intensity Control and PhasingThe MAX6946/MAX6947 use an internal 32kHz oscilla-
tor to generate PWM timing for LED intensity control.
The MAX6946 also features an OSC input to allow for
an external clock for generating PWM timing for LED
intensity control. Select the PWM clock source for the
MAX6946 with configuration register bit D7 (Table 2).
The MAX6947 powers up configured to use the internal
32kHz oscillator by default. The MAX6946 powers up
configured to use the external clock source by default.
A PWM period comprises 256 cycles of the nominal
32kHz PWM clock (Figure 2). Individually set the ports’
PWM duty cycle between 3/256 and 254/256. See
Table 4 for port register settings.
Configure PWM timing by setting the stagger bit in the
configuration register (Table 2), either with output stag-
gering or without. Clearing the stagger bit causes all
outputs using PWM to switch at the same time using
the timing shown in Figure 2. All outputs, therefore,
draw load current at the exactly same time for the same
PWM setting. This means that if, for example, all out-
puts are set to 0x80 (128/256 duty cycle), the current
draw would be zero (all loads off) for half the time, and
full (all loads on) for the other half.
Setting the stagger bit causes the PWM timing of the 10
port outputs to stagger by 32 counts of the 256-count
PWM period (i.e., 1/8th), distributing the port output
switching points across the PWM period (Figure 3).
Staggering reduces the di/dt output-switching transient
on the supply and also reduces the peak/mean current
requirement.
Set or clear the stagger bit during shutdown. Changing
the stagger bit during normal operation can cause a
transient flicker in any PWM-controlled LEDs because
of the fundamental PWM timing changes.
HIGH-Z
LOW
HIGH-Z
LOW
HIGH-Z
LOW
OUTPUT LOW 254/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE)
HIGH-Z
LOW
0xFF
HIGH-Z
LOW
HIGH-Z
LOW
OUTPUT LOW 253/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE)
OUTPUT STATIC-HIGH LOGIC DRIVE WITH INPUT BUFFER ENABLED (GPI)
OUTPUT STATIC-LOW LOGIC DRIVE WITH INPUT BUFFER ENABLED (GPI)
OUTPUT STATIC-LOW CONSTANT CURRENT WITH INPUT BUFFER DISABLED (STATIC LED DRIVE ON)
0xFD
0xFE
0x02
0x00
0x01
OUTPUT STATIC HIGH IMPEDANCE WITH INPUT BUFFER DISABLED (STATIC LED DRIVE OFF)
HIGH-Z
LOWOUTPUT LOW 3/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE)0x03
HIGH-Z
LOW
OUTPUT LOW 252/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE)0xFC
REGISTER
VALUE
OUTPUT
7.8125ms NOMINAL PWM PERIOD
HIGH-Z
LOWOUTPUT LOW 4/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE)0x04
Figure2. Static and PWM Constant-Current Waveforms
MAX6946/MAX6947
Ports Configured as InputsConfigure a port as a logic input by writing 0x01 to the
port’s output register (Table 4). Reading an input port
register returns the logic levels from the I/O ports con-
figured as a logic input (Table 7). The input port regis-
ter returns logic 0 in the appropriate bit position for a
port not configured as a logic input.
The input port’s registers are read only. The MAX6946/
MAX6947 ignore a write to input ports register.
RSTInputThe active-low RSTinput operates as a reset that voids
any current I2C transaction involving the MAX6946/
MAX6947, forcing the devices into the I2C stop condi-
tion. Use the D6 bit in the configuration register to con-
figure RSTto reset all the internal registers to the
power-on reset state (Tables 2 and 3). The RST input is
overvoltage tolerant to 6V.
The MAX6946/MAX6947 ignore all I2C bus activity while
RSTremains low. The MAX6946/MAX6947 use this fea-
ture to minimize supply current in power-critical applica-
tions by effectively disconnecting the MAX6946/
MAX6947 from the bus during idle periods. RSTalso
operates as a bus multiplexer, allowing multiple
MAX6946/MAX6947s to use the same I2C slave address.
Drive only one MAX6946/MAX6947 RSTinput high at any
time to use RSTas a bus multiplexer.
The MAX6946/MAX6947 feature a Reset Run option so
that simply taking the RSTinput high brings the driver
out of shutdown in addition to its normal function of
enabling the devices’ I2C interface.
Standby Mode and Operating CurrentConfiguring all the ports as logic inputs or outputs (all
output registers set to value 0x00 or 0x01) or LED off
(output register set to value 0xFF) puts the MAX6946/
MAX6947 into standby mode. Put the MAX6946/
MAX6947 into standby mode for lowest supply-current
consumption.
Setting a port as a constant-current output increases
the operating current (output register set to a value
between 0x02 and 0xFE), even if a load is not applied
to the port. The MAX6946/MAX6947 enable an internal
current mirror to provide the accurate constant-current
sink. Enabling the internal current mirror increases the
devices’ supply current. Each output contains a gated
mirror, and each mirror is only enabled when required.
In PWM mode, the current mirror is only turned on for
the output’s on-time. This means that the operating cur-
rent varies as constant-current outputs are turned on
and off through the serial interface, as well as by the
PWM intensity control.
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control7.8125ms NOMINAL PWM PERIODNEXT PWM PERIODNEXT PWM PERIOD326496128160192224256
OUTPUTS P0, O8 IN-PHASE PWM PERIOD
OUTPUT P1, O9 STAGGERED PWM PERIOD
OUTPUT P3 STAGGERED PWM PERIOD
OUTPUT P4 STAGGERED PWM PERIOD
OUTPUT P5 STAGGERED PWM PERIOD
OUTPUT P6 STAGGERED PWM PERIOD
OUTPUT P7 STAGGERED PWM PERIOD
OUTPUTS P0, O8 IN-PHASE PWM PERIOD
OUTPUT P1, O9 STAGGERED PWM PERIOD
OUTPUT P3 STAGGERED PWM PERIOD
OUTPUT P4 STAGGERED PWM PERIOD
OUTPUT P5 STAGGERED PWM PERIOD
OUTPUT P6 STAGGERED PWM PERIOD
OUTPUT P7 STAGGERED PWM PERIOD
OUTPUTS P0, O8 IN-PHASE PWM PERIOD
OUTPUT P1, O9 STAGGERED PWM PERIOD
OUTPUT P2 STAGGERED PWM PERIODOUTPUT P2 STAGGERED PWM PERIOD
Figure3. Staggered PWM Waveform
Table7. Input Ports Registers
REGISTER BITDESCRIPTIONADDRESS
CODE (HEX)D7D6D5D4D3D2D1D0Input ports
P7–P00x0EPort P7Port P6Port P5Port P4Port P3Port P2Port P1Port P0
Input ports
P9 and P80x0F000000Port P9Port P8
