MAXIM MAX6966, MAX6967 User Manual

General Description

The MAX6966/MAX6967 serial-interfaced peripherals provide microprocessors with 10 I/O ports rated to 7V.

Each port can be individually configured as either:

• A 20mA constant-current LED driver (static or pulsewidth modulated (PWM)).

• A 10mA constant-current LED driver (static or PWM).

• An open-drain logic output.

• An overvoltage-protected Schmitt logic input.

Analog and switching LED intensity control is built in:

• Individual 8-bit PWM control per output.

• Individual 1-bit analog control (half/full) per output.

• Global 3-bit analog control applies to all LED outputs.

PWM timing of the 10 port outputs may be optionally staggered, consecutively phased in 45° increments. This spreads the PWM load currents over time in eight steps, helping to even out the power-supply current and reduce the RMS current.

The MAX6966/MAX6967 can be configured to awake from shutdown on receipt of a minimum 3ms pulse on the CS input. This hardware-wakeup feature allows a power-management controller or similar ASIC to enable the MAX6966/MAX6967 with preconfigured LED intensity settings.

Shutdown can be programmed to wait up to 4s, fade down the sink currents to zero for a period of 1/16s to 4s, and then shut down. A similar ramp-up from shutdown can be programmed for 1/16s to 4s.

The MAX6966/MAX6967 support hot insertion. All port pins remain high impedance in power-down (V+ = 0V) with up to 8V asserted on them.

The DOUT/OSC pin can be configured as either the serial interface data output or optional PWM clock input. The MAX6966 powers up defaulting as DOUT output. The MAX6967 defaults as OSC input.

For a similar part without the constant-current controls, refer to the MAX7317 data sheet.

Applications

LCD Backlights RGB LED Drivers

Keypad Backlights Portable Equipment

LED Status Indication Cellular Phones

Features

♦ High-Speed 26MHz SPI-™/QSPI-™/MICROWIRE™-

Compatible Serial Interface

♦ 2.25V to 3.6V Operation

♦ I/O Ports Default to High-Z (LEDs Off) on Power-Up

♦ I/O Port Inputs Are Overvoltage Protected to 7V

♦ I/O Port Outputs Are 7V-Rated Open Drain

♦ I/O Port Outputs Are 10mA or 20mA Constant-

Current Static/PWM LED Drivers, or Open-Drain Logic Outputs

♦ I/O Ports Support Hot Insertion

♦ Individual 8-Bit PWM Intensity Control for Each LED

♦ Any Output May Use or Not Use PWM Control ♦ Exit Shutdown (Warm Start) with Simple CS Pulse

♦ Auto Ramp-Down into Shutdown

♦ Auto Ramp-Up Out from Shutdown

♦ 0.8µA (typ), 2µA (max) Shutdown Current

♦ Tiny 3mm x 3mm, 0.8mm High Thin QFN Package

♦ -40°C to +125°C Temperature Range

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O

Expanders with PWM Intensity Control

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3487; Rev 2; 4/05

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

EVALUATION KIT

AVAILABLE

PART

TEMP

PINPACKAGE

TOP

PKG

CODE

MAX6966ATE

-40°C to

16 Thin QFN 3mm x 3mm x

0.8mm

T1633-4

MAX6966AEE

-40°C to 16 QSOP — —

MAX6967ATE

-40°C to

16 Thin QFN 3mm x 3mm x

0.8mm

T1633-4

MAX6967AEE

-40°C to 16 QSOP — —

SPI and QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor Corp.

RANGE

+125°C

MARK

ACF

ACG

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O Expanders with PWM Intensity Control

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

Voltage (with respect to GND)

V+ .............................................................................-0.3V to +4V

SCLK, DIN, CS, DOUT/OSC.........................-0.3V to (V+ + 0.3V)

P_ .............................................................................-0.3V to +8V

DC Current into P_ .............................................................24mA

DC Current into DOUT/OSC................................................10mA

Total GND Current ............................................................280mA

Continuous Power Dissipation

16-Pin QSOP (derate 8.3mW/°C over T

= +70°C) ....667mW

16-Pin QFN (derate 14.7mW/°C over T

= +70°C)...1176mW

Operating Temperature Range (T

MIN

to T

MAX

).-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(Typical Operating Circuit, V+ = 2.25V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at V+ = 3.3V, TA=

+25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Operating Supply Voltage V+

Output Load External Supply Voltage P0–P9

EXT

TA = +25°C 0.7 1.5

1.7

Standby Current (Interface Idle, CS Run Disabled, PWM Disabled, All Ports High Impedance)

STBY

CS at V+; other digital inputs at V+ or GND

1.9

µA

TA = +25°C

Supply-Current Interface Only (CS Run Enabled, PWM Disabled, All Ports High Impedance)

SCLK

= 26MHz, other

digital inputs at V+ or

µA

TA = +25°C

1.8

1.9

Delta Supply Current per 10mA Port (Interface Idle, Global Current Register Set to 0x07, One Port's Output Register Set to 0x02 and Its Output Current Register Bit Cleared; All Other Ports’ Output Registers Set to 0x00, 0x01, or 0xFF)

∆I

+10

Digital inputs at V+ or GND

TA = +25°C 3.2 3.6

3.8

Delta Supply Current per 20mA Port ( Inter face Id l e, Gl ob al C ur r ent Reg i ster S et to 0x07, One P or t' s Outp ut Reg i ster S et to 0x02 and Its Outp ut C ur r ent Reg i ster Bi t S et; Al l Other P or ts’ Outp ut Reg i ster s S et to 0x00, 0x01, or 0xFF)

∆I

+20

Digital inputs at V+ or GND

4.0

2.25 3.60

GND; DOUT unloaded

TA= T

TA = T

to +85°C

MIN

to T

MIN

MAX

to +85°C 680

MIN

= T

to T

MIN

MAX

to +85°C

MIN

to T

MIN

to +85°C

MIN

to T

MIN

MAX

390 620

730

1.58

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O

Expanders with PWM Intensity Control

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Typical Operating Circuit, V+ = 2.25V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at V+ = 3.3V, TA=

+25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Input High Voltage (P0–P9, DIN, SCLK, CS, OSC)

P0–P9: output register set to 0x01

0.7 x V+

Input Low Voltage (P0–P9, DIN, SCLK, CS, OSC)

P0–P9: output register set to 0x01

0.3 x V+

Input Leakage Current (P0–P9, DIN, SCLK, CS, OSC)

, I

µA

Input Capacitance (P0–P9, DIN, SCLK, CS, OSC)

(Note 2) 10 pF

TA = +25°C

9.5 10

Port Nominal Sink Constant Current (P0–P9) (Global Current Register Set to 0x07)

OUT

Output register set to 0x02, V+ = 3.3V, V

EXT

- V

LED

1V to 2.5V (Note 3)

= T

MIN

+85°C

9.1

Port Logic Output Low Voltage (P0–P9)

OLP_

Output register set to 0x00, I

SINK

= 0.5mA

0.4 V

Port Logic Output Low ShortCircuit Current (P0–P9)

Output register set to 0x00, V

OLP_

= 5V

20 mA

Port Slew Time From 20% current to 80% current 2 µs

TA = +25°C, V+ = 3.3V, V

EXT

- V

LED

= 1.4V,

OUT

= 20mA

±4

Port Sink Constant-Current Matching

∆I

OUT

TA = +25°C, V+ = 3.3V, V

EXT

- V

LED

= 1.4V,

OUT

= 10mA

±2 ±5

Output High Voltage (DOUT)

SOURCE

= 6mA

V+ -

Output Low Voltage (DOUT)

SINK

= 6mA 0.3 V

-0.2 +0.2

19.3

18.8 21.8

10.8

±1.5

21.1

10.7

11.0

OHDOUT

OLDOUT

0.3V

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O Expanders with PWM Intensity Control

4 _______________________________________________________________________________________

TIMING CHARACTERISTICS

(Typical Operating Circuit, V+ = 2.25V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at V+ = 3.3V, TA=

+25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Internal PWM Clock Frequency f

INT

External PWM Clock Frequency f

OSC

kHz

SCLK Clock Period t

SCLK Pulse Width High t

19 ns

SCLK Pulse Width Low t

19 ns

CS Fall to SCLK Rise Setup Time

CSS

9.5 ns

SCLK Rise to CS Rise Hold Time

CSH

0ns

DIN Setup Time t

9.5 ns

DIN Hold Time t

0ns

Output Data Propagation Delay t

21 ns

DOUT Output Rise and Fall Times

LOAD

= 20pF 10 ns

Minimum CS Pulse High t

CSW

CS Pulse Low to Not Activate CS Run

CSRUN

CS run enabled

µs

CS Pulse Width to Activate CS Run

CSRUN

CS run enabled 3 ms

Note 1: All parameters tested at TA= +25°C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design. Note 3: Port current is factory trimmed to meet a median sink current of 20mA and 10mA over all 10 ports. The ∆I

OUT

specification

guarantees current matching between ports.

27000 45000

100

38.4

640

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O

Expanders with PWM Intensity Control

_______________________________________________________________________________________ 5

STANDBY CURRENT (I

STBY1

)

vs. TEMPERATURE

MAX6966/67 toc01

TEMPERATURE (°C)

STANDBY CURRENT (µA)

11095-25 -10 5 35 50 6520 80

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0.4

-40 125

V+ = 3.6V

V+ = 3.3V

V+ = 2.7V

V+ = 2.25V

SUPPLY CURRENT (I+)

vs. TEMPERATURE

MAX6966/67 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

1109580655035205-10-25

0.1

0.2

0.3

0.4

0.5

-40 125

V+ = 3.6V

V+ = 3.3V

V+ = 2.7V

V+ = 2.25V

OUTPUT SINKING CURRENT

vs. V

EXT

- V

LED

AT 10mA

MAX6966/67 toc03

EXT

- V

LED

(V)

OUTPUT SINKING CURRENT (mA)

4321

OUTPUT SINKING CURRENT

vs. V

EXT

- V

LED

AT 20mA

MAX6966/67 toc04

EXT

- V

LED

(V)

OUTPUT SINKING CURRENT (mA)

4321

INTERNAL OSCILLATOR FREQUENCY

vs. TEMPERATURE

MAX6966/67 toc05

TEMPERATURE (°C)

FREQUENCY (kHz)

1109565 80-10 5 20 35 50-25

-40 125

V+ = 3.6V

V+ = 3.3V

V+ = 2.7V

V+ = 2.25V

SAMPLE PWM WAVEFORMS

2ms

OUTPUT

= 0x03

OUTPUT

= 0x80

OUTPUT

= 0xFE

MAX6966/67 toc06

STAGGER PWM PORT WAVEFORMS

(OUTPUT REGISTERS SET TO 0x80)

2ms

PORT P4

PORT P0

PORT P1

MAX6966/67 toc07

MAX6966/MAX6967

Quick-Start Guide

This section describes how to configure a MAX6966 or MAX6967 on power-up.

Software engineers can use this section as a plain-text guide to the device’s initialization routine. Hardware engineers can use this section to get a quick overview of the device’s capabilities and feature tradeoffs:

1) Before power-up, all 10 I/O ports P0 to P9 are high impedance. They may be connected to inputs up to +7V or loads connected to independent rails up to +7V. The SPI bus inputs (SCLK, CS, DIN) are not overvoltage protected, and must not be driven from a voltage higher than V+.

2) After power-up, all 10 I/O ports P0 to P9 remain high impedance. They may be connected to inputs up to +7V or loads connected to V+ or independent rails up to +7V. The ports are not configured as logic inputs even though the ports are high impedance. The device is in shutdown mode, and draws minimum supply current regardless of I/O ports connections.

3) Decide whether the DOUT/OSC pin will be used as SPI data output or PWM clock input, and choose the MAX6966 or MAX6967 accordingly. If

any ports are used as logic input, or if the application needs read-after-write validation, then DOUT/OSC needs to be configured as DOUT. Note that both the MAX6966 and MAX6967 can configure DOUT/OSC as either DOUT output or OSC clock input; the only difference is the power-up default.

4) Allocate port functionality for the 10 I/O ports. All ports have the same features, so allocate ports for either software convenience or board-routing reasons. Any port can be constant-current LED drivers (static or PWM), an open-drain logic output, or a logic input. If fewer than 10 ports are used as constant-current drivers, see the Applications Information section for details on how to optimize the PWM phasing to minimize load supply-current modulation.

5) Decide how to implement LED intensity control. The MAX6966/MAX6967 provide:

• Individual 8-bit PWM control per constant-current

output

• Individual 1-bit analog control (half/full) per

constant-current output

• Global 3-bit analog control, which applies to all

constant-current outputs

10-Port Constant-Current LED Drivers and I/O Expanders with PWM Intensity Control

6 _______________________________________________________________________________________

Pin Description

QSOP

NAME FUNCTION

1 15 SCLK

Serial-Clock Input. On SCLK’s rising edge, data shifts into the internal shift register. On SCLK’s falling edge, data is clocked out of DOUT. SCLK is active only while CS is low.

216 CS

Chip-Select Input. Serial data is loaded into the shift register while CS is low. The most recent 16 bits of data latch on CS’s rising edge.

3–7,

9-13

7-11

P0-P9

I/O Ports. P0 to P9 can be configured as open-drain current-sink outputs rated at 20mA maximum, or as CMOS-logic inputs, or as open-drain logic outputs. Loads should be connected to a supply voltage no higher than 7V.

8 6 GND Ground

14 12

Serial-Data Output. The data into DIN is valid at DOUT 15.5 clock cycles later. Use this pin to daisy-chain several devices or allow data readback. Output is push-pull. OSC Input. Apply a square-wave CMOS clock up to 100kHz as alternate PWM clock source.

The MAX6966 powers up with DOUT/OSC defaulting as DOUT output. The MAX6967 powers up with DOUT/OSC defaulting as OSC input.

15 13 DIN

Serial-Data Input. Data from DIN loads into the internal 16-bit shift register on SCLK’s rising edge.

16 14 V+ Positive Supply Voltage. Bypass V+ to GND with a 0.1µF ceramic capacitor.

— PAD

Exposed

pad

Exposed Pad on Package Underside. Connect to GND.

TQFN

1–5,

DOUT/OSC

The tradeoff for LED intensity control is between depth of current-control resolution, noise constraints, and software complexity:

• For high LED resolution where each LED needs individual intensity settings, use the 8-bit PWM control plus the 1-bit analog control to get 9 bits of individual LED intensity control.

• For absolute maximum LED resolution where the LED uses the same intensity settings, use the 8bit PWM control plus the 1-bit analog control, plus the global 3-bit analog control to get 12 bits of LED intensity control.

• For lowest noise applications where PWM cannot be used, 1 bit of individual analog control is available. If all LEDs use the same intensity settings, the 1-bit analog control plus the global 3bit analog control provide 4 bits of static LED intensity control.

• If the standard half/full constant-current settings of 10mA/20mA are not acceptable, then the global 3-bit analog control can be used to reduce the currents for all the constant-current outputs.

6) Take care with PC board layout. The MAX6966/ MAX6967 are switching moderate currents in PWM applications, so the MAX6966/MAX6967 and the load supplies need careful decoupling to minimize conducted noise. Also, the serial interface is fast, so

simple overshoot-damping terminations may be required if the tracks are long.

Detailed Description

The MAX6966/MAX6967 are general-purpose input/output (GPIO) peripherals that provide 10 I/O ports, P0 to P9, controlled through a high-speed SPI-compatible serial interface. The 10 I/O ports can be used as logic inputs, open-drain logic outputs, or constant-current sinks in any combination. Ports withstand 7V independent of the MAX6966’s or MAX6967’s supply voltage whether used as logic inputs, logic outputs, or constant-current sinks.

Ports configured as constant-current outputs can be set to sink either a constant current of either 10mA or 20mA. The static port current may be PWM with a duty cycle ranging from 3/256 to 254/256 to reduce the average current, or remain static.

Ports configured as open-drain logic outputs have a relatively weak sink capability, which should still be adequate for normal logic-level outputs. Open-drain logic outputs typically require external pullup resistors to the appropriate positive supply to provide the logichigh reference. The weak drive means that the shortcircuit current is low enough that inadvertently driving an LED from a port configured as a logic output is unlikely to damage the LED.

The MAX6966/MAX6967 are rated for all 10 outputs to carry their maximum 20mA loads at the same time. The port configuration options are shown in Table 1.

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O

Expanders with PWM Intensity Control

_______________________________________________________________________________________ 7

PORT TYPE

OUTPUT

CODE

BEHAVIOR OUT OF

SHUTDOWN (CONFIGURATION

BEHAVIOR IN SHUTDOWN

(CONFIGURATION REGISTER

BIT D0 = 0)

APPLICATION NOTES

Low-logic output

0x00 Logic-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

Constantcurrent static sink output

0x02

Static constant-current sink

output

Full constant-current drive

with no PWM noise

Constantcurrent PWM output

High impedance

Adjustable constant current

LED off 0xFF

Logic-high output with external pullup resistor; otherwise, high

impedance

LED off

Table 1. Port Configuration Options

0x03–0xFE PWM constant-current sink output

MAX6966/MAX6967

Figure 1 shows the I/O port structure of the MAX6966/

MAX6967. I/O ports P0 to P9 default to high impedance on power-up, so LED or other port loads connected draw no current, and ports used as inputs do not load their source signals.

Standby Mode and Operating Current

When all the ports are configured as logic inputs or outputs (all output registers set to value 0x00 or 0x01) or LED off (output register set to value 0xFF), the MAX6966/MAX6967 operate at their lowest supply current, called standby mode.

When PWM intensity control is used (one or more output registers set to a value between 0x03 and 0xFE), the operating current increases because the internal PWM circuitry is running.

The operating current also increases whenever a port that is set is active low as a constant-current output (output register set to a value between 0x02 and 0xFE), even if a load is not applied to the port. This current increase is due to an internal current mirror being enabled for that port output to provide the accurate constant-current sink. There is a gated mirror for each output, and each mirror is only enabled when required. When PWM is used, a current mirror is only turned on for the output’s on-time. This means that operating current varies as constant-current outputs are turned on

and off through the serial interface, as well as by the PWM intensity control.

Shutdown Mode

In shutdown mode, all ports configured as constant-current outputs (output register set to a value between 0x02 and 0xFE) are switched off, and these outputs go high impedance as if their registers were set to value 0xFF. Ports configured as logic inputs or outputs (output registers set to value 0x00 or 0x01) are unaffected (Table 1). This means that any ports used for GPIOs are still fully operational in shutdown mode, and port inputs can be read and output ports can be toggled at any time using the serial interface. The MAX6966/MAX6967 can therefore be used for a mix of logic inputs, logic outputs, and PWM LED drivers, and only the LED drivers are turned off automatically in shutdown.

The MAX6966/MAX6967 are put into shutdown mode by clearing the run bit (bit D0) in the configuration register (Table 4). Shutdown is exited by setting the run bit through the serial interface, or by using the CS run option discussed below. The MAX6966/MAX6967 can be configured and controlled in the normal way through the serial interface in shutdown mode. All registers are accessible in shutdown mode, and no register is changed by shutdown mode. When shutdown mode is exited, ports configured as constant-current outputs at that time start instantly with their current PWM values.

10-Port Constant-Current LED Drivers and I/O Expanders with PWM Intensity Control

8 _______________________________________________________________________________________

Figure 1. Simplified Schematic of I/O Ports

I/O PORT

8-BIT LATCH

OUTPUT PORT

1-BIT LATCH

TO/FROM

SERIAL

INTERFACE

OUTPUT CURRENT

3-BIT LATCH

GLOBAL CURRENT

PORT COMMAND

READ I/O

POSITION A: 0x00 - 0x01 POSITION B: 0x02 - 0xFF

CLOSE SWITCH: 0x02-0xFE

MSB

PWM

GENERATOR

4-BIT DAC

ENABLE

SET

CURRENT

ENABLE = 0x00

If a port is changed from static logic low (0x00) or static logic high (0x01) to a constant-current value (0x02–0xFE) in shutdown mode, then that output is automatically turned off (logic high, or high impedance) like any other constant-current outputs that are disabled in shutdown. When shutdown mode is exited, the new constant-current output starts just like any other constant-current outputs.

If a port is changed from a constant-current value (0x02–0xFE) to static logic low (0x00) or static logic high (0x01) in shutdown mode, then that output is instantly set to that value as a GPIO output. When shutdown mode is exited, the new GPIO output is unaffected just like any other GPIO outputs.

CS Run Option

The MAX6966/MAX6967 can be configured so that a relatively long pulse on the CS input brings the driver out of shutdown, as an alternative method to the normal method of writing the configuration register through the serial interface. When the CS run option is enabled, a minimum pulse on CS sets the run bit in the configuration register, bringing the driver out of shutdown and activating any preconfigured ramp-up. Also, the SPI interface must be operated at a minimum data rate to ensure that a normal active-low CS pulse during a 16bit regular data transmission is not mistaken for a CS run command.

The CS run timing uses the PWM clock, which is either the internal nominal 32kHz oscillator or a user-provided clock fed into the dual-use DOUT/OSC pin (see the PWM Clock section for details on configuring the PWM clock).

The minimum pulse on CS to trigger CS run and bring the driver out of shutdown is 256 to 257 periods of the PWM clock. For the internal oscillator, this time is 257 / 27000 = 9.52ms. For the external PWM clock, this time is 257 / OSC and has a shortest possible time of

2.57ms when OSC is set to the maximum allowed

100kHz frequency.

The maximum pulse on CS to ensure that CS run is not triggered (when enabled) is 255 periods of the PWM clock. For the internal oscillator, this time is 255 / 45000 = 5.66ms. Since a transmission on the serial interface comprises 16 clocks with CS low, a minimum 2.83kHz SCLK frequency ensures that CS run is not triggered. For the external PWM clock, this time is 255 / OSC and has a shortest time of 2.55ms when OSC is set to the maximum allowed frequency of 100kHz.

The SPI serial interface circuitry is independent of the CS run circuitry. Activity on SCLK and DIN is ignored by the CS run circuitry. A slow SPI transmission to the MAX6966/MAX6967 can therefore be used as both a valid data transmission (read or write), and as a means for exiting shutdown. The CS run action (i.e., setting the run bit in the configuration register) occurs before any coincident data transmission is processed. This means that a slow transmission containing a write command to the configuration register clearing the run bit would work, since the write command is implemented internally after the CS run action that sets the run bit.

The "slow transmission" cut-off data rate is expected to be lower than the SPI interface speed in the majority of applications. If this is not the case, the CS run option can still be used. Consider the situation when the MAX6966/MAX6967 have been put into shutdown with the CS run option enabled. The application uses the MAX6966/MAX6967 with some ports configured as logic inputs or outputs, which need to be accessed in shutdown. The SPI interface speed is slow, so any transmission brings the MAX6966/MAX6967 out of shutdown. So, how are the I/O ports accessed in shutdown? The solution is to write the configuration register disabling CS run (bit D1 = 0) and invoking shutdown (bit D0 = 0) as the first command. Now any other registers can be accessed while the MAX6966/MAX6967 remain in shutdown. Finally, write the configuration register reenabling CS run (bit D1 = 1) and invoking shutdown (bit D0 = 0) to restore the original status.

MAX6966/MAX6967

10-Port Constant-Current LED Drivers and I/O

Expanders with PWM Intensity Control

_______________________________________________________________________________________ 9

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