TEXAS INSTRUMENTS SN75970B Technical data

SN75970B

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

D

Provides High-Voltage Differential SCSI
from Single-Ended Controller When Used

DGG OR DL PACKAGE

(TOP VIEW)

With the SN75971B Data Transceiver

D

Nine Transceivers Meet or Exceed the
Requirements of ANSI Standard EIA-485
and ISO-8482 Standards

D

ESD Protection on Bus Pins to 12 kV

D

Packaged in Shrink Small-Outline Package
with 25 mil Terminal Pitch and Thin
Small-Package with 20 mil Terminal Pitch

D

Low Disabled Supply Current 32 mA Typ

D

Thermal Shutdown Protection

D

Positive- and Negative-Current Limiting

D

Power-Up/-Down Glitch Protection

D

Open-Circuit Failsafe Receivers

description

The SN75970B SCSI differential converter­control, when used in conjunction with one or
more of its companion data transceiver(s),
provides the superior electrical performance of
differential SCSI from a single-ended SCSI bus
controller. A 16-bit, Fast-SCSI bus can be
implemented with just three devices (two for data
and one for control) in the space-efficient, 56-pin,
shrink small-outline package (SSOP) as well as
the even smaller TSSOP and a few external
components.

The SN75970B is available in a B2 (20 Mxfer)

RSTFLTR

RESET

DSENS

CLK40

GND

AATN–

TEST

AACK–

TIMEOUT

AREQ–

AC/D–

V

CC

GND
GND
GND
GND
GND

V

CC

DRVBUS

SDB

AMSG–

AI/O–

ASEL–

NC

ABSY–

NC

ARST–

NC

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29

X2
X1/CLK20
NC
BATN–
BATN+
BACK–
BACK+
BREQ–
BREQ+
BC/D–
BC/D+
V

CC

GND
GND
GND
GND
GND
V

CC

BMSG–
BMSG+
BI/O–
BI/O+
BSEL+
BSEL–
BBSY+
BBSY–
BRST+
BRST–

version and a B1 (10 Mxfer) version.

NC – No internal connection

In a typical differential SCSI node, the SCSI
controller provides the enables for each external

Terminals 13 through 17 and 40 through 44 are
connected together to the package lead frame and
signal ground.

RS-485 transceiver. This could require as many
as 27 additional terminals for a 16-bit differential bus controller or relegate a 16-bit single-ended controller to
only an 8-bit differential bus. Using the standard nine SCSI control signals, the SN75970B control transceiver
decodes the state of the bus and enables the SN75971B data transceiver(s) to transmit the single-ended SCSI
input signals differentially to the cable or receive the differential cable signals and drive the single-ended outputs
to the controller.

The single-ended SCSI bus interface consists of CMOS bidirectional inputs and outputs. The drivers are rated
at ±16 mA of output current. The receiver inputs are pulled high with approximately 4 mA to eliminate the need
for external pullup resistors for the open-drain outputs of most single-ended SCSI controllers. The single-ended
side of the device is not intended to drive the SCSI bus directly.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Copyright  2000, Texas Instruments Incorporated

1

SN75970B
SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

description (continued)

The differential SCSI bus interface consists of
bipolar bidirectional inputs and outputs that meet
or exceed the requirements of EIA-485 and ISO
8482-1982/TIA TR30.2 referenced by the Ameri­can National Standard of Information Systems
(ANSI) X3.131-1994 Small Computer System
Interface-2 (SCSI-2) and SCSI-3 Fast-20 Parallel
Interface (Fast-20) X3.277:1996.

The SN75970B is characterized for operation
over the temperature range of 0°C to 70°C.

The SN75970B consists of nine RS-485 differen­tial transceivers, nine TTL- or CMOS-level
compatible transceivers, a state machine and
control logic block, a 20-MHz crystal-controlled
oscillator, a timer, a power-up/-down glitch
protection circuit, and a thermal-shutdown
protection circuit.

The single-ended or controller interface is
designated as the A side and the differential port
is the B side. Since the device uses the SCSI
control signals to decode the state of the bus and
data flow direction, the terminal assignments must
be matched to the corresponding signal on the
SCSI bus. The signal name followed by a a minus
sign (–) indicates an active-low signal while a plus
sign (+) indicates an active-high signal.

A reset function, which disables all outputs and
clears internal latches, can be accomplished from
two external inputs and two internally generated
signals. RESET
sense) are available to external circuits for a bus
reset or to disable all outputs should a
single-ended cable be inadvertently connected to
a differential connector. The power-up and
thermal-shutdown are internally generated sig­nals that have the same effect when the supply
voltage is below 3.5 V or the junction temperature
exceeds approximately 175°C.

This data sheet contains descriptions of the
SN75970B input and output signals followed by
the electrical characteristics. The parameter
measurement information is followed by the
theory of operation, a state flow chart, and a
typical circuit in the application information
section.

(Reset) and DSENS (differential

logic diagram (positive logic)

AC/D–

AI/O–

TEST

CLK40

6

8

21

11

10

22

27

25

23

3
7
2
1
4

55
56

X2

State Machine and

Control Logic

Oscillator

Power-Up

and Reset Logic

H

H

H

H

Shutdown

AATN–

AACK–

AMSG–

AREQ–

ARST–

ABSY–

ASEL–

DSENS

RESET

RSTFLTR

X1/CLK20

Thermal

53
52

51
50

38
37

47
46

49
48

36
35

30
29

32
31

34
33

19

20

9

BATN–
BATN+

BACK–
BACK+

BMSG–
BMSG+

BC/D–
BC/D+

BREQ–
BREQ+

BI/O–
BI/O+

BRST+
BRST–

BBSY+
BBSY–

BSEL+
BSEL–

DRVBUS

SDB

TIMEOUT

2

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SCSI DIFFERENTIAL CONVERTER-CONTROL

I/O

TERMINATION

DESCRIPTION

Terminal Functions

SN75970B

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

TERMINAL

NAME NO.

AACK– 8 TTL I/O strong pullup SCSI acknowledge (–ACK) signal to/from controller
AATN– 6 TTL I/O strong pullup SCSI attention (–ATN) signal to/from controller
ABSY– 25 TTL I/O strong pullup SCSI busy (–BSY) signal to/from the controller
AC/D– 11 TTL I/O strong pullup SCSI control/data (–C/D) signal to/from the controller
AI/O– 22 TTL I/O strong pullup SCSI input/output (–I/O) signal to/from the controller
AMSG– 21 TTL I/O strong pullup SCSI message (–MSG) signal to/from the controller

AREQ– 10 TTL I/O strong pullup SCSI request (–REQ) signal to/from controller
ARST– 27 TTL I/O strong pullup SCSI reset (–RST) signal to/from the controller
ASEL– 23 TTL I/O strong pullup SCSI select (–SEL) signal to/from the controller
BACK– 51 RS-485 I/O weak pullup SCSI acknowledge (–ACK) signal to/from the bus
BACK+ 50 RS-485 I/O weak pulldown SCSI acknowledge (+ACK) signal to/from the bus
BATN– 53 RS-485 I/O weak pullup SCSI attention (–ATN) signal to/from the bus
BATN+ 52 RS-485 I/O weak pulldown SCSI attention (+ATN) signal to/from the bus
BBSY– 31 RS-485 I/O weak pulldown SCSI busy (–BSY) signal to/from the bus
BBSY+ 32 RS-485 I/O weak pullup SCSI busy (+BSY) signal to/from the bus
BC/D– 47 RS-485 I/O weak pullup SCSI control/data (–C/D) signal to/from the bus
BC/D+ 46 RS-485 I/O weak pulldown SCSI control/data (+C/D) signal to/from the bus
BI/O– 36 RS-485 I/O weak pullup SCSI input/output (–I/O) signal to/from the bus
BI/O+ 35 RS-485 I/O weak pulldown SCSI input/output (+I/O) signal to/from the bus
BMSG– 38 RS-485 I/O weak pullup SCSI message (–MSG) signal to/from the bus
BMSG+ 37 RS-485 I/O weak pulldown SCSI message (+MSG) signal to/from the bus
BREQ– 49 RS-485 I/O weak pullup SCSI request (–REQ) signal to/from the bus
BREQ+ 48 RS-485 I/O weak pulldown SCSI request (+REQ) signal to/from the bus
BRST– 29 RS-485 I/O weak pulldown SCSI reset (–RST) signal to/from the bus
BRST+ 30 RS-485 I/O weak pullup SCSI reset (+RST) signal to/from the bus
BSEL– 33 RS-485 I/O weak pulldown SCSI select (–SEL) signal to/from the bus
BSEL+ 34 RS-485 I/O weak pullup SCSI select (+SEL) signal to/from the bus
CLK40 4 CMOS I strong pulldown 40-MHz clock input
DRVBUS 19 TTL O N/A Driver bus. A high-level logic signal that indicates the SCSI bus is in one of

DSENS 3 TTL I weak pullup A low-level input initializes the internal latches and disables all drivers.
GND 5, 13–17,

RESET 2 TTL I weak pullup Reset. A low-level input initializes the internal latches and disables all drivers.
RSTFLTR 1 TTL I weak pullup Reset filter. Filtered input from the SCSI bus for a system reset. RSTFLTR

SDB 20 TTL O N/A A high-level logic signal that indicates a differential to single-ended data flow.
TEST 7 TTL I weak pulldown Test. A high-level input that places the device in a test mode (see Table 1).

TIMEOUT 9 Analog I/O N/A Time out. This signal connects to an external RC time constant for a time out

V

CC

X1/CLK20 55 CMOS I none 20-MHz crystal oscillator or clock input
X2 56 Analog O none 20-MHz crystal oscillator feedback

40–44

12, 18, 39, 45 N/A N/A N/A 5-V supply voltage

LOGIC
LEVEL

the information transfer phases.

N/A N/A N/A Supply common

differs from RESET by keeping the ARST and BRST drivers enabled.

It is grounded during normal operation.

during bus arbitration.

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3

SN75970B
SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

schematics of inputs and outputs

Input

Input

RSTFLTR

200 Ω

200 Ω

, RESET, AND DSENS

22 k

CLK40

V

X1/CLK20, X2

CC

V

Input

V

CC

CC

4 mA

Input

200 Ω

A, SDB, DRVBUS

200 Ω

A

TEST

V

50 kΩ

CC

TIMEOUT

V

CC

Input

B+ AND B– Inputs

V

CC

100 kΩ
B– Pin Only

Input

18 kΩ

100 kΩ
B+ Pin Only

B+ AND B– Outputs

200 Ω

12 kΩ

V

CC

3 kΩ

V

1 kΩ

CC

V

CC

X1/CLK20

X2

200 Ω

100 kΩ

Output

B–

V

CC

18 kΩ

B+

Output

4

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SN75970B

High-level input voltage, V

V

Low-level input voltage, V

V

gy ( y

B side–7V

High-level output current, I

mA

Low-level output current, I

Clock frequenc

f

MH

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

Supply voltage range, V

Differential bus voltage range (B side) –10 V to 15 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signal-ended bus voltage range (A side and control) –0.3 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous total power dissipation See Dissipation Rating Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrostatic discharge: B side (see Note 2):Class 3, A: 12 kV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating free-air temperature range, T
Storage temperature range, T

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

†

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 under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTES: 1. All voltage values are with respect to the GND terminals.

2. This absolute maximum rating is tested in accordance with MIL-STD-883C, Method 3015.7.

PACKAGE

DGG 3333 mW 26.7 mW/°C 2133 mW

‡

This is the inverse of the traditional junction-to-case thermal resistance (R
JEDEC) PCB installations.

(see Note 1) –0.3 V to 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC

Class 3, B: 400 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

All terminals: Class 2, A: 4 kV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Class 2, B: 400 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0°C to 70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

POWER RATING

DL 3709 mW 29.7 mW/°C 2374 mW

A

DISSIPATION RATING TABLE

TA ≤ 25°C

OPERATING FACTOR

ABOVE TA = 25°C

‡

TA = 70°C

POWER RATING

θJA

) for High-K (per

†

recommended operating conditions

Supply voltage, V

Input voltage at any bus terminal (separately or
common-mode), V

Operating case temperature, T
Operating free-air temperature, T

CC

p

p

p

p

y,

IH

IL

I

OH

OL

CLK

C

A

MIN NOM MAX UNIT

4.75 5 5.25 V
A side, DSENS, TEST, RESET, AND RSTFLTR 2
CLK40 AND X1/CLK20 0.7 V
A side, DENS, TEST, RESET, and RSTFLTR 0.8
CLK40 AND X1/CLK20 0.2 V

A side, DRVBUS, SDB, TIMEOUT –16
X2 –4
A side, DRVBUS, and SDB 16 mA
X2 4 mA
CLK20 20
CLK40 40

CC

CC

12

0 125 °C
0 70 °C

z

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5

SN75970B

See Figure 1
VOLLow-level output voltage

V

V

gg

V

V

ggg

V

V

y

IIBus input current

B side

mA

IH

IIHHigh-level in ut current

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP

V

OD(H)

V

OD(L)

V

OH

IT+

IT–

hys

†

All typical values are at VCC = 5 V, TA = 25°C.

‡

The algebraic convention with the least positive (more negative) limit is designated minimum, is used in this data sheet for the differential input
voltage only .

Driver differential
high-level output voltage

Driver differential
low-level output voltage

High-level output voltage

p

Receiver positive-going
input threshold voltage

Receiver negative-going
input threshold voltage

Receiver input hysteresis
(V

– V

IT+

-

)

IT–

p

p

B side except BBSY,
BRST, and BSEL

B side
AACK–, AA TN–,

AC/D–, AI/O–,
AMSG–, AREQ–

DRVBUS, SDB IOH = –16 mA 2.5 4.4
TIMEOUT
B side 3.4

X2 IOH = - 4 mA 3.2
DRVBUS, SDB IOL = 16 mA 0.8
A side VID = 200 mV, IOL = 16 mA 0.8
B side 1.6
X2 IOL = 4 mA 0.8
B side IOH = –16 mA, See Figure 2 0.2
TIMEOUT
B side IOL = 16 mA, See Figure 2 –0.2
TIMEOUT
B side 45 mV
TIMEOUT

A side –2.0 –6 –8 mA
DSENS, RESET,

RSTFLTR
CLK40, X1/CLK20
TEST 100

TIMEOUT

VID = –200 V, IOH = –16 mA 2.5 4.3

Test and RESET at 0.8 V,
All others open, IOH = –16 mA

VI = 12 V, VCC = 5 V,
All other inputs at 0 V

VI = 12 V, VCC = 0,
All other inputs at 0 V

VI = –7 V, VCC = 5 V,
All other inputs at 0 V

VI = –7 V, VCC = 0,
All other inputs at 0 V

V

= 2 V

TEST at 2 V, A side and other
control inputs at 0.8 V ,
B side open, VIH = 2 V

–0.8 –2.2 V

1 1.8 V

2.5 4.5

‡

0.32V

CC

0.5 V

†

MAX UNIT

2.6

0.4 V

CC

0.6 1

0.7 1

–0.5 –0.8

–0.4 –0.8

–60 –100

±20

±25

V

µA

6

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SN75970B

IL

IILLow-level in ut current

CpdPower dissipation capacitance (see Note 3)

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted) (Continued)

PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT

A side –6 –9 mA
DSENS, RESET,

RSTFLTR

-

p

I

OS

I

CC

C

o

†

All typical values are at VCC = 5 V, TA = 25°C.

NOTE 3: Cpd determines the no-load dynamic current consumption, IS = Cpd × VCC × f + ICC (ICC depends upon the output states and load circuits

Short circuit output current B side VO = 5 V and 0 V ±250 mA

Supply current

Bus output capacitance

p

and is not necessarily the same ICC as specified in the electrical tables).

p

CLK40, X1/CLK20
TEST ±30

TIMEOUT

Disabled RESET at 0.8 V, All others open 32 42
All A-side to B-side

channels enabled

All B-side to A-side
channels enabled

V

= 0.8 V

TEST at 2 V, A side and other
control inputs at 0.8 V ,
B side open, VIL = 0.8 V

TEST and RSTFLTR at 2 V
RESET

at 0.8 V,

All other inputs open, No load
TEST and B+ pins at 2 V, RESET,

RSTFLTR, and B– pins
All other inputs open, No load

B side to GND,
VI = 0.6 sin(2π 106 t)+ 1.5 V

B side to A side, one channel 40 pF
A side to B side, one channel 100 pF

at 0.8 V,

–100

±30

µA

±25

72 95

mA

51 72

18 21 pF

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7

SN75970B

See Figure 3

3.5

17.7

B1

AREQ

BREQ±

t

t

l

ns

See Figure 3

5.5

15.7

B2

AREQ

BREQ±

t

Ske

part-to-part

ns

t

Pulse ske

ns

B1

BREQ±

AREQ

t

t

l

ns

B2

BREQ±

AREQ

t

Skew part-to-part

ns

t

Pulse ske

ns

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

switching characteristics over recommended operating free-air temperature range (unless
otherwise noted)

PARAMETER

’

,

d1

sk(pp)

sk(p)

d3,

sk(pp)

sk(p)

†

All typical values are at VCC = 5 V, TA = 25°C.

NOTES: 4. Part-to-part skew is the magnitude of the difference in propagation delay times between any two devices when both operate with

Delay time, A to B, high- to

d2

d4

ow-level or low- to high-lev-

el output

’

’B1

p

w,

Delay time, B to A, high- to

ow-level or low- to high-lev-

el output

the same supply voltages, the same temperature, and the same loads.

5. Pulse skew is the difference between the high-to-low and low-to-high propagation delay times of any single channel.

p

’B2

’B1

w

’B2

’

’

’B1

p

p

’B2

’B1

w

’B2

FROM

(INPUT)TO(OUTPUT)

AATN–

AC/D–

AI/O–

AMSG–

AACK––BACK±

AATN–

AC/D–

AI/O–

AMSG–

AACK––BACK±

AACK–

AREQ–

AACK–

AREQ–

AACK–

AREQ–

AACK–

AREQ–

BATN±

BC/D±

BI/O±

BMSG±

BACK±

BATN±

BC/D±

BI/O±

BMSG±

BACK±

BACK±

BREQ±

BACK±

BREQ±

BACK±

BREQ±

BACK±

BREQ±

BATN±

BC/D±

BI/O±

BMSG±

–

BATN±

BC/D±

BI/O±

BMSG±

–

BACK±
BREQ±

BACK±
BREQ±

BACK±
BREQ±

BACK±
BREQ±

AATN–

AC/D–

AI/O–

AMSG–

AACK–

–

–

AATN–

AC/D–

AI/O–

AMSG–

AACK–

–

–

AACK–
AREQ–

AACK–
AREQ–

AACK–
AREQ–

AACK–
AREQ–

TEST CONDITIONS MIN TYP†MAX UNIT

3.1 15.3
VCC = 5 V, TA = 25°C 4.2 12.2
VCC = 5 V, TA = 70°C 4.7 12.7

4.5 13.3
VCC = 5 V, TA = 25°C 6.2 10.2
VCC = 5 V, TA = 70°C 6.7 10.7

See Note 4 8

See Note 4 4

See Note 5 8

See Note 5 4

See Figure 4 5.1 17.9

5.3 18
VCC = 5 V, TA = 25°C 6.3 15.2
VCC = 5 V, TA = 70°C 6.7 15.6

See Figure 4 7.3 14.6

7.5 14.2
VCC = 5 V, TA = 25°C 8.5 13
VCC = 5 V, TA = 70°C 8.9 13.4

See Note 4 9

See Note 4 4.5

See Note 5 8

See Note 5 4

8

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SN75970B

TIMEOUT

DRVBUS

See Figure 5

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

switching characteristics over recommended operating free-air temperature range (unless
otherwise noted) (continued)

PARAMETER

t

PHL

t

PLH

t

dis

t

en

t

dis1

t

dis2

t

dis3

t

en1

t

en2

t

en3

t

en4

†

All typical values are at VCC = 5 V, TA = 25°C.

Delay time, high- to low-level
Delay time, low- to high-level

Disable time

Enable time

Disable time BRST± ARST– 93 ns
Disable time BSEL± ASEL– 55 ns
Disable time BBSY± ABSY– 60 ns
Enable time BRST± ARST–
Enable time BSEL± ASEL– 45 ns
Enable time BBSY± ABSY– 45 ns
Enable time BSEL± ASEL– 92 ns

FROM

(INPUT)TO(OUTPUT)

ABSY– BBSY± 200
ARST–

ASEL– BSEL± 200
ABSY– BBSY± 40
ARST–

ASEL– BSEL± 39

BRST±

BRST±

TEST CONDITIONS MIN TYP†MAX UNIT

200 ns
200 ns

See Figure 6

See Figure 6

See Figure 7

200

ns

ns

55

63 ns

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9