A6276

16-Bit Serial Input, Constant-Current Latched LED Driver

Last Time Buy

This part is in production but has been determined to be
LAST TIME BUY. This classification indicates that the product is
obsolete and notice has been given. Sale of this device is currently
restricted to existing customer applications. The device should not be
purchased for new design applications because of obsolescence in the
near future. Samples are no longer available.

Date of status change: November 1, 2010

Deadline for receipt of LAST TIME BUY orders: April 30, 2011

Recommended Substitutions:

For existing customer transition, and for new customers or new appli-
cations, contact Allegro Sales.

NOTE: For detailed information on purchasing options, contact your

local Allegro field applications engineer or sales representative.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
 A6276
16-Bit Serial Input, Constant-Current
Latched LED Driver
Features and Benefits Description
▪ Up to 90 mA constant-current outputs The A6276 is specifically designed for LED-display
▪ Undervoltage lockout applications. Each BiCMOS device includes a 16-bit CMOS
▪ Low-power CMOS logic and latches shift register, accompanying data latches, and 16 NPN constant-
▪ High data input rate current sink drivers. Except for package style and allowable
▪ Functional replacement for TB62706BN/BF package power dissipation, the device options are identical.
The CMOS shift register and latches allow direct interfacing
with microprocessor-based systems. With a 5 V logic supply,
typical serial data-input rates are up to 20 MHz. The LED drive
current is determined by the user selection of a single resistor.
Packages A CMOS serial data output permits cascaded connections in
applications requiring additional drive lines. For inter-digit
blanking, all output drivers can be disabled with an ENABLE
24-pin DIP input high. Similar 8-bit devices are available as the A6275.
(A package) Two package styles are provided: through-hole DIP (suffix A)
and surface-mount SOIC (suffix LW). In normal applications,
the copper leadframe and low logic-power dissipation of the
24-pin SOICW DIP allow it to sink maximum rated current through all outputs
(LW package) continuously over the operating temperature range (90 mA,
0.75 V drop, 85°C). Both packages are lead (Pb) free, with
100% matte tin leadframe plating.
Not to scale

Functional Block Diagram

26185.201I
 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

Selection Guide
Ambient
Part Number Package Packing
Temperature (°C)
A6276EA-T 24-pin DIP 15 per tube –40 to 85
A6276ELWTR-T 24-pin SOICW 1000 per reel –40 to 85

Absolute Maximum Ratings*

Characteristic Symbol Notes Rating Units
Supply Voltage VDD 7.0 V
Output Voltage VO –0.5 to 17 V
Input Voltage VROUT –0.4 to VDD + 0.4 V
Output Current IO 90 mA
Ground Current IGND 1475 mA
Operating Ambient Temperature TA Range E –40 to 85 ºC
Maximum Junction Temperature TJ(max) 150 ºC
Storage Temperature Tstg –55 to 150 ºC
*Caution: These CMOS devices have input static protection (Class 2) but are still susceptible to damage if exposed to extremely high
static electrical charges.

Thermal Characteristics may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions* Value Units
Package A, 1-layer PCB based on JEDEC standard 50 ºC/W
Package Thermal Resistance RθJA
Package LW, 1-layer PCB based on JEDEC standard 85 ºC/W

*Additional thermal information available on the Allegro website

4.0

3.5
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

3.0
24-PIN DIP, RQJA = 50°C/W

2.5
24-LEAD SOIC, RQJA = 85°C/W

2.0

1.5

1.0

0.5

0
25 50 75 100 125 150
AMBIENT TEMPERATURE IN ° C
*Mounted on single-layer, two-sided PCB, with 3.8 in2 copper each side;
additional information on Allegro Web site

Allegro MicroSystems, Inc. 2

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1.508.853.5000; www.allegromicro.com
 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

Pin-out Diagram
(A and LW packages)

V DD LOGIC
GROUND 1 24
SUPPLY
SERIAL IO
2 23 R EXT
DATA IN REGULATOR
SERIAL
CLOCK 3 CK 22 DATA OUT

LATCH 4 L OE 21 OUTPUT
ENABLE ENABLE
REGISTER
OUT 0 5 LATCHES 20 OUT 15

OUT 1 6 19 OUT 14

OUT 2 7 18 OUT 13

OUT 3 8 17 OUT 12

OUT 4 9 16 OUT 11

OUT 5 10 15 OUT 10

OUT 6 11 14 OUT 9

OUT 7 12 13 OUT 8

Terminal Description

Terminal No. Terminal Name Function

1 GND Reference terminal for control logic.
2 SERIAL DATA IN Serial-data input to the shift-register.
3 CLOCK Clock input terminal for data shift on rising edge.
4 LATCH ENABLE Data strobe input terminal; serial data is latched with high-level input.
5-20 OUT0-15 The 16 current-sinking output terminals.
21 OUTPUT ENABLE When (active) low, the output drivers are enabled; when high, all output
drivers are turned OFF (blanked).
22 SERIAL DATA OUT CMOS serial-data output to the following shift-register.
23 REXT An external resistor at this terminal establishes the output current for all
sink drivers.
24 SUPPLY (VDD) The logic supply voltage (typically 5 V).

Allegro MicroSystems, Inc. 3

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Copyright © 2000, 2003 Allegro MicroSystems, Inc.

 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

V DD

V DD

IN IN

Dwg. EP-010-11 Dwg. EP-010-12

OUTPUT ENABLE (active low) LATCH ENABLE

V DD V DD

IN OUT

Dwg. EP-063-6

Dwg. EP-010-13

CLOCK and SERIAL DATA IN SERIAL DATA OUT

TRUTH TABLE
Serial Shift Register Contents Serial Latch Latch Contents Output Output Contents
Data Clock Data Enable Enable
Input Input I1 I2 I3 ... IN-1 IN Output Input I1 I2 I3 ... IN-1 IN Input I1 I2 I3 ... IN-1 IN

H H R1 R2 ... RN-2 RN-1 RN-1

L L R1 R2 ... RN-2 RN-1 RN-1

X R1 R2 R3 ... RN-1 RN RN

X X X ... X X X L R1 R2 R3 ... RN-1 RN

P1 P2 P3 ... PN-1 PN PN H P1 P2 P3 ... PN-1 PN L P1 P2 P3 ... PN-1 PN

X X X ... X X H H H H ... H H
L = Low Logic (Voltage) Level H = High Logic (Voltage) Level X = Irrelevant P = Present State R = Previous State

Allegro MicroSystems, Inc. 4

115 Northeast Cutoff
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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

ELECTRICAL CHARACTERISTICS at TA = +25°C, VDD = 5 V (unless otherwise noted).

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Unit

Supply Voltage Range VDD Operating 4.5 5.0 5.5 V

Under-Voltage Lockout VDD(UV) VDD = 0 5 V 3.4 – 4.0 V

Output Current IO VCE = 0.7 V, REXT = 250  64.2 75.5 86.8 mA

(any single output)
VCE = 0.7 V, REXT = 470  34.1 40.0 45.9 mA

Output Current Matching ∆IO 0.4 V VCE(A) = VCE(B) 0.7 V:

(difference between any REXT = 250  – ±1.5 ±6.0 %
two outputs at same VCE)
REXT = 470  – ±1.5 ±6.0 %

Output Leakage Current ICEX VOH = 15 V – 1.0 5.0 μA

Logic Input Voltage VIH 0.7VDD – VDD V

VIL GND – 0.3VDD V

SERIAL DATA OUT VOL IOL = 500 μA – – 0.4 V

Voltage
VOH IOH = -500 μA 4.6 – – V

Input Resistance RI ENABLE Input, Pull Up 150 300 600 k

LATCH Input, Pull Down 100 200 400 k

Supply Current IDD(OFF) REXT = open, VOE = 5 V – 0.8 1.4 mA

REXT = 470 Ω, VOE = 5 V 3.5 6.0 8.0 mA

REXT = 250 Ω, VOE = 5 V 6.5 11 15 mA

IDD(ON) REXT = 470 , VOE = 0 V 7.0 13 20 mA

REXT = 250 , VOE = 0 V 10 22 32 mA

Typical Data is at VDD = 5 V and is for design information only.

Allegro MicroSystems, Inc. 5

115 Northeast Cutoff
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1.508.853.5000; www.allegromicro.com
 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

SWITCHING CHARACTERISTICS at TA = 25°C, VDD = VIH = 5 V, VCE = 0.4 V, VIL = 0 V,

REXT = 470 Ω, IO = 40 mA, VL = 3 V, RL = 65 Ω, CL = 10.5 pF.

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Unit

Propagation Delay Time tpHL CLOCK-OUTn – 350 1000 ns

LATCH-OUTn – 350 1000 ns

ENABLE-OUTn – 350 1000 ns

CLOCK-SERIAL DATA OUT – 40 – ns

Propagation Delay Time tpLH CLOCK-OUTn – 300 1000 ns

LATCH-OUTn – 300 1000 ns

ENABLE-OUTn – 300 1000 ns

CLOCK-SERIAL DATA OUT – 40 – ns

Output Fall Time tf 90% to 10% voltage 150 350 1000 ns

Output Rise Time tr 10% to 90% voltage 150 300 600 ns

RECOMMENDED OPERATING CONDITIONS

Characteristic Symbol Conditions Min. Typ. Max. Unit

Supply Voltage VDD 4.5 5.0 5.5 V

Output Voltage VO – 1.0 4.0 V

Output Current IO Continuous, any one output – – 90 mA

IOH SERIAL DATA OUT – – -1.0 mA

IOL SERIAL DATA OUT – – 1.0 mA

Logic Input Voltage VIH 0.7VDD – VDD + 0.3 V

VIL -0.3 – 0.3VDD V

Clock Frequency fCK Cascade operation – – 10 MHz

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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

TIMING REQUIREMENTS and SPECIFICATIONS

(Logic Levels are VDD and Ground)

CLOCK 50%

A B

SERIAL DATA 50%

DATA IN

tp

SERIAL 50% DATA

DATA OUT

D E

LATCH
50%
ENABLE

OUTPUT
ENABLE LOW = ALL OUTPUTS ENABLED

tp HIGH = OUTPUT OFF

OUT N 50% DATA

A. Data Active Time Before Clock Pulse
LOW = OUTPUT ON (Data Set-Up Time), tsu(D) ............................. 50 ns
Dwg. WP-029-1
B. Data Active Time After Clock Pulse
(Data Hold Time), th(D) ................................. 20 ns
C. Clock Pulse Width, tw(CK) .................................. 50 ns
D. Time Between Clock Activation
HIGH = ALL OUTPUTS DISABLED (BLANKED)
and Latch Enable, tsu(L) ............................... 100 ns
OUTPUT 50% E. Latch Enable Pulse Width, tw(L) ...................... 100 ns
ENABLE
F t pLH F. Output Enable Pulse Width, tw(OE) ................... 4.5 μs
tf tr

90%
50%
NOTE: Timing is representative of a 10 MHz clock. Sig-
OUT N DATA
t pHL 10% nificantly higher speeds are attainable.
Max. Clock Transition Time, tr or tf ....................... 10 μs
Dwg. WP-030-1A

Serial data present at the input is transferred to the shift long as the LATCH ENABLE is held high. Applications where
register on the logic 0-to-logic 1 transition of the CLOCK input the latches are bypassed (LATCH ENABLE tied high) will
pulse. On succeeding CLOCK pulses, the registers shift data in- require that the OUTPUT ENABLE input be high during serial
formation towards the SERIAL DATA OUTPUT. The serial data data entry.
must appear at the input prior to the rising edge of the CLOCK When the OUTPUT ENABLE input is high, the output sink
input waveform. drivers are disabled (OFF). The information stored in the latches
Information present at any register is transferred to the is not affected by the OUTPUT ENABLE input. With the OUT-
respective latch when the LATCH ENABLE is high (serial-to- PUT ENABLE input low, the outputs are controlled by the state
parallel conversion). The latches continue to accept new data as of their respective latches.

Allegro MicroSystems, Inc. 7

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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

ALLOWABLE OUTPUT CURRENT AS A FUNCTION OF DUTY CYCLE

A6276EA A6276ELW
100 100
VCE = 1 V VCE = 0.7 V
ALLOWABLE OUTPUT CURRENT IN mA/BIT

ALLOWABLE OUTPUT CURRENT IN mA/BIT

VCE = 1 V
80 80
VCE = 2 V
VCE = 3 V VCE = 2 V

60 60
VCE = 3 V
VCE = 4 V

VCE = 4 V
40 40

TA = +25oC TA = +25oC
20 VDD = 5 V 20 VDD = 5 V
RQJA = 50oC/W RQJA = 75oC/W

0 0
0 20 40 60 80 100 0 20 40 60 80 100

DUTY CYCLE IN PER CENT DUTY CYCLE IN PER CENT

Dwg. GP-062-11 Dwg. GP-062-6

100 100
VCE = 1 V VCE = 0.7 V
ALLOWABLE OUTPUT CURRENT IN mA/BIT
ALLOWABLE OUTPUT CURRENT IN mA/BIT

80 80
VCE = 2 V VCE = 1 V

VCE = 3 V
60 VCE = 2 V
60

VCE = 3 V
VCE = 4 V

40 40
VCE = 4 V

TA = +50oC TA = +50oC
20 VDD = 5 V 20 VDD = 5 V
RQJA = 50oC/W RQJA = 75oC/W

0 0
0 20 40 60 80 100 0 20 40 60 80 100
DUTY CYCLE IN PER CENT DUTY CYCLE IN PER CENT
Dwg. GP-062-10 Dwg. GP-062-7

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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

ALLOWABLE OUTPUT CURRENT AS A FUNCTION OF DUTY CYCLE (cont.)

A6276EA A6276ELW
100 100

VCE = 0.7 V VCE = 0.4 V

ALLOWABLE OUTPUT CURRENT IN mA/BIT

ALLOWABLE OUTPUT CURRENT IN mA/BIT

80 VCE = 1 V 80
VCE = 0.7 V

VCE = 1 V

60 VCE = 2 V 60

VCE = 3 V VCE = 2 V

VCE = 3 V
40 40
VCE = 4 V
VCE = 4 V

TA = +85oC TA = +85oC
VDD = 5 V 20 VDD = 5 V
20
RQJA = 50oC/W RQJA = 75oC/W

0 0
0 20 40 60 80 100 0 20 40 60 80 100

DUTY CYCLE IN PER CENT DUTY CYCLE IN PER CENT

Dwg. GP-062-8
Dwg. GP-062-9

TYPICAL CHARACTERISTICS

60
OUTPUT CURRENT IN mA/BIT

40

20 TA = +25oC
REXT = 500 7

0
0 0.5 1.0 1.5 2.0
VCE IN VOLTS
Dwg. GP-063

Allegro MicroSystems, Inc. 9

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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

Applications Information

The load current per bit (IO) is set by the external resistor diode (VZ), or a series string of diodes (approximately
(REXT) as shown in the figure below. 0.7 V per diode) for a group of drivers. If the available
voltage source will cause unacceptable dissipation and
100
series resistors or diode(s) are undesirable, a regulator
such as the Sanken Series SAI or Series SI can be used to
80
V CE = 0.7 V
provide supply voltages as low as 3.3 V.
For reference, typical LED forward voltages are:
White 3.5 – 4.0 V
60
Blue 3.0 – 4.0 V
Green 1.8 – 2.2 V
40 Yellow 2.0 – 2.1 V
Amber 1.9 – 2.65 V
Red 1.6 – 2.25 V
20 Infrared 1.2 – 1.5 V
Pattern Layout. This device has a common logic-ground
0 and power-ground terminal. If ground pattern layout
2k 3k 5k
100 200 300 500 700 1k
contains large common-mode resistance, and the voltage
CURRENT-CONTROL RESISTANCE, R EXT IN OHMS
Dwg. GP-061
between the system ground and the LATCH ENABLE or
Package Power Dissipation (PD). The maximum al- CLOCK terminals exceeds 2.5 V (because of switching
lowable package power dissipation is determined as noise), these devices may not operate correctly.
PD(max) = (150 - TA)/RJA.
The actual package power dissipation is
PD(act) = DC • (VCE • IO • 16) + (VDD • IDD) ,
V
where DC is the duty cycle. LED

When the load supply voltage is greater than 3 V to 5 V,

V DROP
considering the package power dissipating limits of these
devices, or if PD(act) > PD(max), an external voltage re-
ducer (VDROP) should be used.
VF
Load Supply Voltage (VLED). These devices are de-
signed to operate with driver voltage drops (VCE) of
0.4 V to 0.7 V with LED forward voltages (VF) of 1.2 V to V CE
4.0 V. If higher voltages are dropped across the driver,
package power dissipation will be increased significantly.
To minimize package power dissipation, it is recom-
mended to use the lowest possible load supply voltage or Dwg. EP-064

to set any series dropping voltage (VDROP) as

VDROP = VLED - VF - VCE
with VDROP = Io • RDROP for a single driver, or a Zener

Allegro MicroSystems, Inc. 10

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 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

Package A, 24-pin DIP

+0.25
30.10 –0.64

24
+0.10
0.38 –0.05

+0.76 +0.38
6.35 –0.25 10.92 –0.25 7.62

1 2

For Reference Only

5.33 MAX (reference JEDEC MS-001 BE)
Dimensions in millimeters
+0.51
3.30 –0.38 Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
1.27 MIN 2.54 A Terminal #1 mark area

+0.25
1.52 –0.38
0.018
0.46 ±0.12

Package LW, 24-pin SOICW

15.40±0.20
4° ±4 24
24
+0.07 2.20
0.27 –0.06

7.50±0.10 10.30±0.33 9.60

A
+0.44
0.84 –0.43

1 2
1 2 0.65
1.27
0.25

B PCB Layout Reference View

24X C SEATING PLANE
SEATING
0.10 C PLANE GAUGE PLANE

0.41 ±0.10 1.27 For Reference Only

2.65 MAX (Reference JEDEC MS-013 AD)
0.20 ±0.10 Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown

A Terminal #1 mark area

B Reference pad layout (reference IPC SOIC127P1030X265-24M)

All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances

Allegro MicroSystems, Inc. 11

115 Northeast Cutoff
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1.508.853.5000; www.allegromicro.com
 16-Bit Serial Input, Constant-Current
A6276
Latched LED Driver

Copyright ©2000-2009, Allegro MicroSystems, Inc.

The products described here are manufactured under one or more U.S. patents or U.S. patents pending.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to per-
mit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the
information being relied upon is current.
Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use;
nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com

Allegro MicroSystems, Inc. 12

115 Northeast Cutoff
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1.508.853.5000; www.allegromicro.com