Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

853-1930 022368

DESCRIPTION

The SA5777A is a monolithic driver for controlling air-core (or
differential) meters typically used in automotive instrument cluster
applications. The circuit interfaces with a microprocessor through a
serial bus and directly drives the air-core meter. The SA5777A has
10-bit resolution (0.35 degree) and is guaranteed to be monotonic.
Data can be shifted through the part, allowing several SA5777As to
be cascaded with only one chip-select line. On-chip current shut
down logic protects the circuit from external faults.

FEATURES

10-Bit resolution (0.35 degrees)

Exceptional accuracy (0.5 degrees, typical)

High-torque capability

Active differential drivers eliminate back-EMF issues

No RFI/EMI generation issues

Simple serial interface

Simple cascading capability for multiple meters

Internal fault protection

Only one external component required (bypass capacitor)

APPLICATION

Instrumentation utilizing air-core meters

PIN CONFIGURATION

C1+

C1

AGND

VBB

DATAOUT

DATAIN

VCC

SCLK

COM

DGND

AGND

C2-

C2+

N Package

SL00460

D Package

C1+

C1

AGND

VBB

DATAOUT

DATAIN

VCC

SCLK

COM

DGND

AGND

C2-

C2+

Figure 1. Pin configuration

ORDERING INFORMATION

DESCRIPTION

TEMPERATURE RANGE

ORDER CODE

DWG #

16-Pin Plastic Dual In-Line Package (DIP)

-40 to +85

SA5777AN

SOT38-4

28-Pin Plastic Small Outline Package (SO)

-40 to +85

SA5777AD

SOT136-1

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

BLOCK DIAGRAM

9-BIT LATCH

FAULT

DETECTION

7 + BIT

DAC

10-BIT

SHIFT REGISTER

9-BIT LATCH

10-BIT

SHIFT REGISTER

7 + BIT

DAC

MUX

COM

C2+

C1+

VBB

VCC

DIN

SCLK

DOUT

VBB/2

SL00461

Figure 2. Block diagram

Table 1.

SA5777A Pin Descriptions for the N Package (Dual In-Line)

Pin #

Name

Function

Negative output connection to the TAN coil of meter #1.

C1+

Positive output connection to the TAN coil of meter #1.

GND

Ground for V

supply. Pins 3, 12 and 13 should be connected on the circuit board.

Analog supply. Nominally 13.5 V.

DATA

OUT

Serial data output. Output of the internal shift register. When a new data word is shifted in, the old word is shifted out the
DATA

OUT

pin. DATA

OUT

output is always active.

DATA

Serial data input. A new data word is serially shifted into the part on the rising edge of S

CLK

. The data is shifted in MSB

first, gauge 1 first.

5 V logic supply. The internal latches and registers are set to zero on the rising edge of this signal.

Output drivers are turned off when this input is low.

CLK

Serial clock input. Data is loaded into the part on the rising edge of S

CLK

. Data is shifted out of DATA

OUT

on the falling

edge of S

CLK

10.

Active high chip select input. When CS is high, the part is enabled to receive a new serial input word. The high-to-low
transition of CS loads the new 20-bit word into the DAC registers and updates the output.

11.

Status output. This is an open drain output and goes low when the coil output buffers (C1+, C1, C2+, C2, COM) have
been disabled. The coil outputs may be disabled due to shorted outputs, over-temperature conditions, power-on reset,
or by the output enable (OE) pin. Multiple status outputs , ST, may be wire OR'ed together.

12.

GND

Ground for V

supply. Connect to Pins 3 and 13.

13.

GND

Ground for V

supply. Connect to Pins 3 and 12.

14.

COM

Output drive for biased coils. This output will be 1/2 of V

15.

Negative output connection to the TAN coil of meter #2.

16.

C2+

Positive output connection to the TAN coil of meter #2.

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

Table 2.

SA5777A Pin Descriptions for the D Package (Small Outline)

Pin #

Name

Function

Negative output connection to the TAN coil of meter #1.

C1+

Positive output connection to the TAN coil of meter #1.

No connect

GND

Ground for V

supply. Pins 6, 20 and 23 should be connected on the circuit board.

Analog supply. Nominally 13.5 V.

DATA

OUT

Serial data output. Output of the internal shift register. When a new data word is shifted in, the old word is shifted out
the DATA

OUT

pin. DATA

OUT

output is always active.

DATA

Serial data input. A new data word is serially shifted into the part on the rising edge of S

CLK

. The data is shifted in MSB

first, gauge 1 first.

10.

No connect

11.

No connect

12.

No connect

13.

5 V logic supply. The internal latches and registers are set to zero on the rising edge of this signal.

14.

Output drivers are turned off when this input is low.

15.

CLK

Serial clock input. Data is loaded into the part on the rising edge of S

CLK

. Data is shifted out of DATA

OUT

on the falling

edge of S

CLK

16.

17.

No connect

18.

No connect

19.

20.

GND

Ground for V

supply. Connect to Pins 6 and 23.

21.

No connect

22.

No connect

23.

GND

Ground for V

supply. Connect to Pins 6 and 20.

24.

COM

Output drive for biased coils. This output will be 1/2 of V

25.

No connect

26.

No connect

27.

Negative output connection to the TAN coil of meter #2.

28.

C2+

Positive output connection to the TAN coil of meter #2.

ABSOLUTE MAXIMUM RATINGS

SYMBOL

PARAMETER

RATING

UNIT

Analog supply

-1 to +23

Digital supply

-1 to +6

Digital input voltage, Data In, OE, CS, S

CLK

-1 to +6

GND

to A

GND

Ground difference

0.5

Ambient operating temperature

40 to +85

Junction temperature

150

STG

Storage temperature

65 to +150

Power dissipation (T

= 25

N, D packages

1500

DIP and SO packages

C/W

NOTE:
1. For power dissipation ratings in still air, derate above 25

C at the following rates:

N and D packages at 12mW/

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

DC ELECTRICAL CHARACTERISTICS

= 7.5 to 18 V; V

= 4.5 to 5.5 V; T

= 40 to +85

SYMBOL

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Analog supply voltage

7.5

IGN

Analog supply current

IGN

= 18 V no load

= 18 V with load

= R

LMIN

235

Logic supply current

= 5.5 V

1.0

Output high voltage

Data out I

= 800

0.8

Output low voltage

Data out I

= 1.5 mA

0.4

Status

ST, I

= 2.5 mA

0.8

Status

ST, VO (ST) = V

Input high voltage

CS, S

CLK

, DATA

, OE

0.7 x V

Input low voltage

CS, S

CLK

, DATA

, OE

0.3 x V

Input high current

CS, S

CLK

, DATA

, V

= 0.7 x V

Input low current

CS, S

CLK

, DATA

, V

= 0.3 x V

Output function accuracy

= R

LMIN

Degree

Output shut-down current

C1+, C1, C2+, C2, COM
I

SINK

= V

BB (MAX)

= V

BB (MIN)

SOURCE

= V

BB (MAX)

= V

BB (MIN)

85
43
85
43

500
300
500
300

mA
mA
mA
mA

DRIVE

Differential coil drive voltage

= V

BB (MAX)

= R

L (MIN)

0.7 x V

0.8 x V

LMIN

Minimum load resistance

= 85

= 25

= 40

215
171
138

BIAS

Bias voltage

IOB (Source or Sink)

= R

L (MIN)

0.475 x V

0.525 x V

NOTE:
1. V

DRIVE

is the maximum voltage that is applied across the coil, it is equal to (C1+) (C1) or (C2+) (C2).

2. In reference to nominal values in Figure 4. (Based on 7+ bit DAC).

Output Angle (0)

tan

)

) (C)

BIAS

AC ELECTRICAL CHARACTERISTICS

= 7.5 to 18 V; V

= 4.5 to 5.5 V; T

= 40 to +85

SYMBOL

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

CLK

Input frequency

1.60

MHz

CLKH

CLK

high time

175

CLKL

CLK

low time

= 5.5 V

175

TRO

Output rise time DO

0.75 to V

1.2 V, C

= 90 pF

TFO

Output fall time DO

1.2 V to 0.75, C

= 90 pF

TSU

DI set-up time

THI

DI hold time

CSH

Time before first S

CLK

rising edge

CSL

Time after last S

CLK

falling edge

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

FUNCTIONAL DESCRIPTION

The SA5777A dual air-core gauge driver logic Block Diagram shows
the two 10-bit input shift registers and two 9-bit parallel latches, and
two 7+-bit DACs. The MSB is a dummy bit required for compatibility
with the SA5775A. The DACs generate output voltages that are
offset within the supply rails to give the output buffers enough
headroom to operate. With a 14 V supply, the typical output swing is
from 1 V to 11.5 V. The MUX generates the two required quadrants
by switching the 56

data from the DAC to the appropriate output

buffer. The output buffers provide the necessary current to drive the
air-core gauge. The output buffers are always connected to the
coils and can sink and source sufficient current so that inductive
kickback is eliminated during normal operation.

The primary function of the SA5777A IC is to generate the transfer
function that maps an input code into the correct voltages for linearly
controlling the coils of an air-core gauge display (Figure 3). The
SA5777A has been implemented using the tangent drive algorithm.
Therefore, one coil on each meter will be driven with an output
approximating the tangent function, the other coils will be biased at
1/2 V

. The internal DAC is designed to operate over a 7+ bit (56

)

data range. An extended range can be achieved by changing the
relationship between the bias coil and the driver coil. As the current
through the bias coil is reduced, the full scale deflection is
increased. Theoretically, this deflection could approach 180

, but

practical limitations of accuracy, resolution, and torque restrict the
full scale range to approximately 112

(Figure 4). This full scale

range corresponds to a bias coil voltage of 0.5 x V

and a full scale

tangent voltage of 0.744 x V

. The DAC has been tailored to

maintain the meter accuracy at this maximum deflection. The 0.5 x
V

bias coil voltage is obtained by connecting the bias coils of the

two meters in series across V

. This gives bias stability over

temperature. The internal bias generator is used to offset any
inaccuracies due to meter mismatches. This circuit receives
commands via an internal serial data interface port which is SPI
compatible. These parts can be serially cascaded with other
SA5777A ICs and/or SA5775A ICs to interface signals in multi-chip
systems. The SA5777A has a typical resolution of 0.35

over a full

scale deflection of approximately 112

and is guaranteed to be

monotonic. The input data is directly proportional to the displayed
angle in degrees (Figure NO TAG). Input code 0 gives an output
angle of 0

, code 319 (decimal) will generate a full scale output of

112.15

. Codes higher than decimal 319 will not be loaded into the

DAC latches and will leave the coil output buffers unchanged.
However, codes greater than 319 can be shifted through the
SA5777A intact if other parts are cascaded. The SA5777A is
capable of sourcing and sinking up to 100mA per differential driver
to control either one or two air-core gauge displays directly.

On-chip overcurrent and thermal shut-down logic prevents the chip
from overheating due to high current fault conditions. When a
shut-down condition is detected, the protection circuit disables the
coil output buffers (i.e., C1+, C1, C2+, C2, COM). The coil output
buffers remain in this condition until the first falling edge of CS that
occurs after the die temperature has decreased to about 140

C or

the overcurrent condition has been removed. During shut-down, the
digital portion of this IC continues to operate normally.

14.00

12.00

10.00

8.00

6.00

4.00

2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

127

159

191

223

255

287

319

INPUT CODE

C+ C (VOL

TS)

SL00462

Figure 3. Typical output voltage vs input code (V

= 14 V)

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

0.5 x VBB

+56

56

0.744 x VBB

TOTAL SPAN = 112.15

STEP SIZE = 0.35

ASSUMING CODE 0 IS 0

CODE

127

159

191

223

255

287

319

POSITION

56.097

45.194

33.940

22.685

11.430

0.176

11.079

22.333

33.588

44.843

56.097

IDEAL ANGLE(DEGREE)=CODE/319*2* ArcTan (0.744/0.5)ArcTan(0.744/0.5)

SL00463

Figure 4. Total span

120

100

111

127

143

ANGLE (DEGREES)

INPUT CODE

159

175

191

207

223

239

255

271

287

303

SL00464

319

Figure 5. Meter position (degrees) vs input code

Philips Semiconductors

Product specification

SA5777A

Dual air-core gauge driver

1999 Sep 20

TFO

TRO

TCSH

TSCLKH

TSCLKL

THI

TSU

FSCLK

GAUGE 2

GAUGE 1

D10 D11 D12 D13 D14 D15 D16 D17 D18 D19

LSB

MSB LSB

MSB

20 SCLK CYCLES

SCLK

DATAIN

DATAOUT

D19

D18

D19*

D18*

D1*

D0*

80%

20%

TCSL

*DO IS THE PREVIOUSLY LOADED DATA WORD

SL00465

Figure 6. Serial interface timing

Serial Interface

The SA5777A is controlled through a serial interface with the following control functions (reference Figure 6):

CLK

Serial input clock. When CS is high, the rising edge of S

CLK

shifts a new data bit into the SA5777A and the falling edge shifts

the data out of DATA

OUT

Active high chip select. Enables the SA5777A to receive serial input data. The falling edge of CS loads a new 20-bit data word
into the internal DAC registers which updates the tangent coil output buffers (C1+, C1, C2+, C2).

DATA

Serial data input. The data at this pin is shifted into the internal shift register on the rising edge of S

CLK

. Data is shifted in MSB

first, gauge 1 first.

DATA

OUT

Serial data output. This pin is the output of the internal shift register. The data output on this pin is the input data from DATA

pin delayed by 20 clock cycles. This pin can be used to cascade several SA5777As with one CS line to load all of the
SA5777As concurrently.

Power Moding

The SA5777A has a power-on reset capability. On the rising edge
of V

, the internal latches and registers are set to zero and the coil

output buffers (C1+, C1, C2+, C2, COM) are disabled.

Coil Output Buffer Control

The coil buffers (C1+, C1, C2+, C2, COM) are disabled:
1. With the rising edge of V

(power-on reset).

2. When OE is taken low or held low. The data registers for the

outputs can still be updated while OE is low. When OE is taken
high, the current output data value is displayed. A falling edge
on CS will be required to activate the outputs if a fault condition
has occurred prior to the OE going high.

3. Due to an overcurrent condition on either of the coil output

buffers. The coil output buffers will be enabled after the next CS
high-to-low transition; assuming OE is high. If the overcurrent
condition has not been removed, the outputs will immediately
return to their disabled condition. The ST pin will indicate status
of the coil outputs.

4. Due to excessive power dissipation (i.e., thermal shut-down).

The die temperature must go below 140

C before a falling edge

on the CS pin will clear this fault condition and allow the coil
outputs to go active.

Application Notes

The air-core gauge is constructed of two coils would on a cavity at
90

to each other. Inside the cavity there is a disk which is

magnetized on its diameter. The currents through the coils generate
a resultant magnetic vector that causes the magnetic disc to move
until the magnetic fields are aligned. If the ratio of the currents in the
two coils follows the tangent function, then the transfer characteristic
relating the input data to output angle is linear.

Maximum current is when output is at zero and full scale degrees,
T

= 40

C, and R

= 180.

Copper wire has a typical temperature coefficient of 0.4%/C

Philips Semiconductors

Product specification

SA5777A

Dual aircore gauge driver

1999 Sep 20

Philips Semiconductors
811 East Arques Avenue
P.O. Box 3409
Sunnyvale, California 940883409
Telephone 800-234-7381

Date of release: 09-99

Document order number:

9397 750 06444

Philips

Semiconductors

Definitions

Short-form specification -- The data in a short-form specification is extracted from a full data sheet with the same type number and title. For
detailed information see the relevant data sheet or data handbook.

Limiting values definition -- Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one
or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or
at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended
periods may affect device reliability.

Application information -- Applications that are described herein for any of these products are for illustrative purposes only. Philips
Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or
modification.

Disclaimers

Life support -- These products are not designed for use in life support appliances, devices or systems where malfunction of these products can
reasonably be expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications
do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application.

Right to make changes -- Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard
cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no
responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these
products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless
otherwise specified.

Data sheet
status

Objective
specification

Preliminary
specification

Product
specification

Product
status

Development

Qualification

Production

Definition

[1]

This data sheet contains the design target or goal specifications for product development.
Specification may change in any manner without notice.

This data sheet contains preliminary data, and supplementary data will be published at a later date.
Philips Semiconductors reserves the right to make changes at any time without notice in order to
improve design and supply the best possible product.

This data sheet contains final specifications. Philips Semiconductors reserves the right to make
changes at any time without notice in order to improve design and supply the best possible product.

Data sheet status

[1]

Please consult the most recently issued datasheet before initiating or completing a design.

Part Number SA5777A