Maxim MAX3100EPD, MAX3100EEE, MAX3100CPD Datasheet

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_______________General Description

The MAX3100 universal asynchronous receiver transmit­ter (UART) is the first UART specifically optimized for
small microcontroller-based systems. Using an
SPI™/Microwire™ interface for communication with the
host microcontroller (µC), the MAX3100 comes in a com­pact 16-pin QSOP. The asynchronous I/O is suitable for
use in RS-232, RS-485, IR, and opto-isolated data links.
IR-link communication is easy with the MAX3100’s
infrared data association (IrDA) timing mode.

The MAX3100 includes a crystal oscillator and a baud­rate generator with software-programmable divider ratios
for all common baud rates from 300 baud to 230k baud.
A software- or hardware-invoked shutdown lowers quies­cent current to 10µA, while allowing the MAX3100 to
detect receiver activity.

An 8-word-deep first-in/first-out (FIFO) buffer minimizes
processor overhead. This device also includes a flexible
interrupt with four maskable sources, including address
recognition on 9-bit networks. Two hardware-handshak­ing control lines are included (one input and one output).

The MAX3100 is available in 14-pin plastic DIP and small,
16-pin QSOP packages in the commercial and extended
temperature ranges.

________________________Applications

Hand-Held Instruments
Intelligent Instrumentation
UART in SPI Systems
Small Networks in HVAC or Building Control
Isolated RS-232/RS-485: Directly Drives Opto-Couplers
Low-Cost IR Data Links for Computers/Peripherals

____________________________Features

♦ 16-Pin QSOP Package (8-pin SO footprint):

Smallest UART Available

♦ Full-Featured UART:

—IrDA SIR Timing Compatible
—8-Word FIFO Minimizes Processor

Overhead at High Data Rates
—Up to 230k Baud with a 3.6864MHz Crystal
—9-Bit Address-Recognition Interrupt
—Receive Activity Interrupt in Shutdown

♦ SPI/Microwire-Compatible µC Interface
♦ Lowest Power:

—150µA Operating Current at 3.3V
—10µA in Shutdown with Receive Interrupt

♦ +2.7V to +5.5V Supply Voltage in Operating Mode
♦ Schmitt-Trigger Inputs for Opto-Couplers
♦ TX and

RTS Outputs Sink 25mA for Opto-Couplers

MAX3100

SPI/Microwire-Compatible

UART in QSOP-16

________________________________________________________________

Maxim Integrated Products

1

14
13
12
11
10

9
8

1
2
3
4
5
6
7

V

CC

TX
RX
RTSCS

SCLK

DOUT

DIN

TOP VIEW

MAX3100

CTS
X1
X2

GND

SHDN

IRQ

DIP

16
15
14
13
12
11
10

9

1
2
3
4
5
6
7
8

V

CC

TX
RX
RTS
N.C.
CTS
X1
X2

DIN

DOUT

SCLK

CS

N.C.

IRQ

SHDN

GND

MAX3100

QSOP

__________________________________________________________Pin Configurations

19-1259; Rev 0; 7/97

PART

MAX3100CPD
MAX3100CEE 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

14 Plastic DIP
16 QSOP

______________Ordering Information

Typical Operating Circuit appears at end of data sheet.

SPI is a trademark of Motorola, Inc. Microwire is a trademark of National Semiconductor Corp.

MAX3100EPD
MAX3100EEE -40°C to +85°C

-40°C to +85°C 14 Plastic DIP
16 QSOP

MAX3100

SPI/Microwire-Compatible
UART in QSOP-16

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +2.7V to +5.5V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are measured at 9600 baud at TA= +25°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 in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

VCCto GND ...........................................................................+6V

Input Voltage to GND

(

CS, SHDN, X1, CTS, RX, DIN, SCLK) ....-0.3V to (VCC+ 0.3V)

Output Voltage to GND

(DOUT, RTS, TX, X2) ..............................-0.3V to (V

CC

+ 0.3V)

IRQ...........................................................................-0.3V to 6V

TX, RTS Output Current ....................................................100mA

X2, DOUT, IRQ Short-Circuit Duration

(to V

CC

or GND) .........................................................Indefinite

Continuous Power Dissipation (T

A

= +70°C)

Plastic DIP (derate 10.00mW/°C above +70°C) .......... 800mW

QSOP (derate 8.30mW/°C above +70°C).....................667mW

Operating Temperature Ranges

MAX3100C_ _ ......................................................0°C to +70°C

MAX3100E_ _ ...................................................-40°C to +85°C

Storage Temperature Range............................ -65°C to +160°C

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

I

SOURCE

= 25µA, TX only

V

IRQ

= 5.5V

I

SINK

= 4mA

DOUT only, CS = V

CC

Shutdown mode

Active mode

I

SOURCE

= 5mA

V

VCC= 3.3V

VX1= 0V and 5.5V

CONDITIONS

VCC- 0.5

V

OH

Output High Voltage

pF5C

OUT

Output Capacitance

µA±1I

LK

Output Leakage

V0.4V

OL

Output Low Voltage

pF5C

OUT

Output Capacitance

µA±1I

LK

Output Leakage

DOUT, TX, RTS: I

SINK

= 4mA

TX, RTS: I

SINK

= 25mA

V

pF5C

IN

Input Capacitance

V0.3 x V

CC

V

IL

Input Low Voltage

V0.7 x V

CC

V

IH

Input High Voltage

0.4

V

OL

Output Low Voltage

0.9

VX1= 0V and 5.5V

VV

CC

/ 2 0.2 x V

CC

V

IL

Input Low Voltage

V0.7 x VCCV

CC

/ 2V

IH

Input High Voltage

V0.05 x V

CC

V

HYST

Input Hysteresis

µA±1I

IL

Input Leakage

pF5C

IN

Input Capacitance

UNITSMIN TYP MAXSYMBOLPARAMETER

2

I

IN

Input Current µA

25

VCC- 0.5

mA

0.27 1

I

CC

VCCSupply Current in
Normal Mode

SHDN bit = 1 or SHDN = 0,
logic inputs are at 0V or V

CC

µA10I

CC

VCCSupply Current in
Shutdown

With 1.8432MHz crystal;
all other logic inputs are at
0V or V

CC

VCC= 5V
VCC= 3.3V 0.15 0.4

V2.7 5.5V

CC

Supply Voltage

LOGIC INPUTS (DIN, SCLK, CS, SHDN, CTS, RX)

OSCILLATOR INPUT (X1)

OUTPUTS (DOUT, TX, RTS)

IRQ OUTPUT (Open Drain)

POWER REQUIREMENTS

MAX3100

SPI/Microwire-Compatible

UART in QSOP-16

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +2.7V to +5.5V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

C

LOAD

= 100pF

C

LOAD

= 100pF, RCS= 10kΩ

C

LOAD

= 100pF

CONDITIONS

ns100t

CL

SCLK Low Time

ns100t

CH

SCLK High Time

ns238t

CP

SCLK Period

ns0t

DH

DIN to SCLK Hold Time

ns100t

DS

DIN to SCLK Setup Time

ns100t

DO

SCLK Fall to DOUT Valid

ns0t

CSH

CS to SCLK Hold Time

ns100t

CSS

CS to SCLK Setup Time

ns100t

TR

CS High to DOUT Tri-State

ns100t

DV

CS Low to DOUT Valid

UNITSMIN TYP MAXSYMBOLPARAMETER

TX, RTS, DOUT: C

LOAD

= 100pF

(Note 1)

ns10t

r

Output Rise Time

ns200t

CSW

CS High Pulse Width

ns100t

CS0

SCLK Rising Edge
to CS Falling

(Note 1) ns200t

CS1

CS Rising Edge
to SCLK Rising

Figure 1. Detailed Serial-Interface Timing

TX, RTS, DOUT, IRQ: C

LOAD

= 100pF

ns10t

f

Output Fall Time

AC TIMING (Figure 1)

Note 1: t

CS0

and t

CS1

specify the minimum separation between SCLK rising edges used to write to other devices on the SPI bus

and the CS used to select the MAX3100. A separation greater than t

CS0

and t

CS1

ensures that the SCLK edge is ignored.

CS

t

CSS

t

DS

t

DH

t

DV

SCLK

DIN

DOUT

t

CSH

• • •

t

t

CL

CH

• • •

• • •

t

DO

• • •

t

CSH

t

TR

MAX3100

SPI/Microwire-Compatible
UART in QSOP-16

4 _______________________________________________________________________________________

__________________________________________Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

1000

900

0

-40 -20 40 60 100

SUPPLY CURRENT vs. TEMPERATURE

200
100

800
700

MAX3100-01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

0 20 80

600
500

400
300

VCC = 3.3V

VCC = 5V

1.8432MHz CRYSTAL
TRANSMITTING AT

115.2 kbps

10

9

0

-40 -20 40 60 100

SHUTDOWN CURRENT

vs. TEMPERATURE

2
1

8
7

MAX3100-02

TEMPERATURE (°C)

SHUTDOWN CURRENT (µA)

0 20 80

6
5

4
3

VCC = 5V

VCC = 3.3V

1.8432MHz CRYSTAL

700

600

0

0 1 3

4

5

SUPPLY CURRENT vs.

EXTERNAL CLOCK FREQUENCY

100

500

MAX3100-03

EXTERNAL CLOCK FREQUENCY (MHz)

SUPPLY CURRENT (µA)

2

400

300

200

V

CC

= 5V

V

CC

= 3.3V

70
60

0

0 0.20.1 0.6 0.7

0.8

1.0

TX, RTS, DOUT OUTPUT CURRENT

vs. OUTPUT LOW VOLTAGE (V

CC

= 3.3V)

10

50

MAX3100-04

VOLTAGE (V)

OUTPUT SINK CURRENT (mA)

0.3 0.50.4 0.9

40

30

20

RTS

TX

DOUT

400

50

100 10k

1000

100k 1M

SUPPLY CURRENT vs. BAUD RATE

150

100

MAX3100-03a

BAUD RATE (bps)

SUPPLY CURRENT (µA)

200

250

350

300

5V
TRANSMITTING

1.8432 MHz
CRYSTAL

3V
TRANSMITTING

5V
STANDBY

3V
STANDBY

90
80

0

0 0.20.1 0.6 0.7

0.8

1.0

TX, RTS, DOUT OUTPUT CURRENT

vs. OUTPUT LOW VOLTAGE (V

CC

= 5V)

10

70

MAX3100-05

VOLTAGE (V)

OUTPUT SINK CURRENT (mA)

0.3 0.50.4 0.9

60
50

40
30
20

RTS

TX

DOUT

MAX3100

SPI/Microwire-Compatible

UART in QSOP-16

_______________________________________________________________________________________ 5

______________________________________________________________Pin Description

Crystal Connection. X1 also serves as an external clock input. See

Crystal-Oscillator

Operation—X1, X2 Connection

section.

910

General-Purpose Active-Low Input. Read via the CTS register bit; often used for RS-232 clear­to-send input (Table 1).

1011

General-Purpose Active-Low Output. Controlled by the RTS register bit. Often used for
RS-232 request-to-send output or RS-485 driver enable.

1113

Asynchronous Serial-Data (receiver) Input. The serial information received from the modem or
RS-232/RS-485 receiver. A transition on RX while in shutdown generates an interrupt (Table 5).

1214

Asynchronous Serial-Data (transmitter) Output1315

Active-Low Interrupt Output. Open-drain interrupt output to microprocessor.56
Hardware-Shutdown Input. When shut down (SHDN = 0), the oscillator turns off immediately

without waiting for the current transmission to end, reducing supply current to just leakage
currents.

67

Ground78
Crystal Connection. Leave X2 unconnected for external clock. See

Crystal-Oscillator

Operation—X1, X2 Connection

section.

89

Active-Low Chip-Select Input. DOUT goes high impedance when CS is high. IRQ, TX, and RTS
are always active. Schmitt-trigger input.

44

SPI/Microwire Serial-Clock Input. Schmitt-trigger input.33

SPI/Microwire Serial-Data Output. High impedance when CS is high.

22

SPI/Microwire Serial-Data Input. Schmitt-trigger input.11

X1

CTS

RTS

RX

TX

IRQ

SHDN

GND

X2

CS

SCLK

DOUT

DIN

Positive Supply Pin (2.7V to 5.5V)1416
No Connection. Not internally connected.—5, 12

V

CC

N.C.

PIN

QSOP

FUNCTION

DIP

NAME

_______________Detailed Description

The MAX3100 universal asynchronous receiver trans­mitter (UART) interfaces the SPI/Microwire-compatible,
synchronous serial data from a microprocessor (µP) to
asynchronous, serial-data communication ports (RS­232, RS-485, IrDA). Figure 2 shows the MAX3100 func­tional diagram.

The MAX3100 combines a simple UART and a baud-rate
generator with an SPI interface and an interrupt genera­tor. Configure the UART by writing a 16-bit word to a
write-configuration register, which contains the baud rate,
data-word length, parity enable, and enable of the 8-word
receive first-in/first-out (FIFO). The write configuration
selects between normal UART timing and IrDA timing,
controls shutdown, and contains 4 interrupt mask bits.

Transmit data by writing a 16-bit word to a write-data
register, where the last 7 or 8 bits are actual data to be
transmitted. Also included is the state of the transmitted
parity bit (if enabled). This register controls the state of

the RTS output pin. Received words generate an inter­rupt if the receive-bit interrupt is enabled.

Read data from a 16-bit register that holds the oldest
data from the receive FIFO, the received parity data,
and the logic level at the CTS input pin. This register
also contains a bit that is the framing error in normal
operation and a receive-activity indicator in shutdown.

The baud-rate generator determines the rate at which the
transmitter and receiver operate. Bits B0 to B3 in the
write-configuration register determine the baud-rate divi­sor (BRD), which divides down the X1 oscillator frequen­cy. The baud clock is 16 times the data rate (baud rate).

The transmitter section accepts SPI/Microwire data, for­mats it, and transmits it in asynchronous serial format
from the TX output. Data is loaded into the transmit­buffer register from the SPI/Microwire interface. The
MAX3100 adds start and stop bits to the data and
clocks the data out at the selected baud rate (Table 7).

MAX3100

SPI/Microwire-Compatible
UART in QSOP-16

6 _______________________________________________________________________________________

X1

X2

DOUT

BAUD-RATE

GENERATOR

SPI

INTERFACE

BAUD-RATE

GENERATOR

DIN

SCLK

CS

B0

Pt

TX-SHIFT REGISTER

START/STOP-

BIT DETECT

D0t–D7t

RX-SHIFT REGISTER

D0r–D7r

SHDN

FE

RA

XTAL

B1
B2
B3

RX

TX

9

Pt TX-BUFFER REGISTER

9

Pr

RA/FE

(MASKS)

PrRT

RX-BUFFER REGISTER

PrPrRX-BUFFER REGISTER

9

9

I / O

CTS

RTS

IRQ

INTERRUPT

LOGIC

TRANSMIT-DONE (TM)
DATA-RECEIVED (RM)
PARITY (PM)
FRAMING ERROR (RAM)/

RECEIVE ACTIVITY

(SOURCES)

ACTIVITY

DETECT

Figure 2. Functional Diagram

MAX3100

SPI/Microwire-Compatible

UART in QSOP-16

_______________________________________________________________________________________ 7

The receiver section receives data in serial form. The
MAX3100 detects a start bit on a high-to-low RX transi­tion (Figure 3). An internal clock samples data at 16
times the data rate. The start bit can occur as much as
one clock cycle before it is detected, as indicated by
the shaded portion. The state of the start bit is defined
as the majority of the 7th, 8th, and 9th sample of the
internal 16x baud clock. Subsequent bits are also
majority sampled. Receive data is stored in an 8-word
FIFO. The FIFO is cleared if it overflows.

The on-board oscillator can use a 1.8432MHz or

3.6864MHz crystal, or it can be driven at X1 with a 45%
to 55% duty-cycle square wave.

SPI Interface

The bit streams for DIN and DOUT consist of 16 bits,
with bits assigned as shown in the

MAX3100

Operations

section. DOUT transitions on SCLK’s falling

edge, and DIN is latched on SCLK’s rising edge (Figure

4). Most operations, such as the clearing of internal
registers, are executed only on CS’s rising edge. The
DIN stream is monitored for its first two bits to tell the
UART the type of data transfer being executed (Write
Config, Read Config, Write Data, Read Data).

Only 16-bit words are expected. If CS goes high in the
middle of a transmission (any time before the 16th bit),
the sequence is aborted (i.e., data does not get written
to individual registers). Every time CS goes low, a new
16-bit stream is expected. An example of a write con­figuration is shown in Figure 4.

1

RX

BAUD

BLOCK

2 3 4 5 6 7 8 9

ONE BAUD PERIOD

10 11

MAJORITY

CENTER

SAMPLER

12 13 14 15 16

A

Figure 3. Start-Bit Timing

1

CS

SCLK

DIN

DOUT

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

DATA

UPDATED

11 FEN SHDN TM RM PM RAM IR ST PE L B3 B2 B1 B0

R T 00 0 0 0 0 0 0 0 0 0 0 0 0

Figure 4. SPI Interface (Write Configuration)

MAX3100

SPI/Microwire-Compatible
UART in QSOP-16

8 _______________________________________________________________________________________

MAX3100 Operations

Write Operations

Table 1 shows write-configuration data. A 16-bit
SPI/Microwire write configuration clears the receive
FIFO and the R, T, RA/FE, D0r–D7r, D0t–D7t, Pr, and Pt
registers. RTS and CTS remain unchanged. The new
configuration is valid on CS’s rising edge if the transmit
buffer is empty (T = 1) and transmission is over. If the
latest transmission has not been completed, the regis­ters are updated when the transmission is over (T = 0).

The write-configuration bits (FEN, SHDNi, IR, ST, PE, L,
B3–B0) take effect after the current transmission is
over. The mask bits (TM, RM, PM, RAM) take effect
immediately after the 16th clock’s rising edge at SCLK.

Read Operations

Table 2 shows read-configuration data. This register
reads back the last configuration written to the

MAX3100. The device enters test mode if bit 0 = 1. In
this mode, if CS = 0, the RTS pin acts as the 16x clock
generator’s output. This may be useful for direct baud­rate generation (in this mode, TX and RX are in digital
loopback).

Normally, the write-data register loads the TX-buffer
register. To change the RTS pin’s state without writing
data, set the TE bit. Setting the TE bit high inhibits the
write command (Table 3).

Reading data clears the R bit and interrupt IRQ (Table 4).

Register Functions

Table 5 shows read/write operation and power-on reset
state (POR), and describes each bit used in program­ming the MAX3100. Figure 5 shows parity and word­length control.

14

0
T

6
D6t
D6r

7
D7t
D7r

15 2

DIN 1 D2t

DOUT R D2r

BIT 3

D3t
D3r

0
D0t
D0r

1
D1t
D1r

4
D4t
D4r

5
D5t
D5r

10

TE

RA/FE

11

0
0

8
Pt
Pr

9
RTS
CTS

12

0
0

13

0
0

14

0
T

6
0

D6r

7
0

D7r

15 2

DIN 0 0

DOUT R D2r

BIT 3

0

D3r

0
0

D0r

1
0

D1r

4
0

D4r

5
0

D5r

10

0

RA/FE

11

0
0

8
0

Pr

9

0
CTS

12

0
0

13

0
0

Table 3. Write Data (D15, D14 = 1, 0)

Table 4. Read Data (D15, D14 = 0, 0)

14

1
T

6
0

ST

7
0

IR

15 2

DIN 0 0

DOUT R B2

BIT 3

0

B3

0

TEST

B0

1
0

B1

4
0
L

5
0

PE

10

0

RM

11

0

TM

8
0

RAM

9

0

PM

12

0

SHDNo

13

0

FEN

Table 2. Read Configuration (D15, D14 = 0, 1)

6

ST

0

7

IR

0

2

B2

0

3

B3

0

0

B0

0

1

B1

0

4
L
0

5

PE

0

10

RM

0

11

TM

0

8

RAM

0

9

PM

0

12

SHDNi

0

13

FEN

0

15 14

1
T

DIN 1

DOUT R

BIT

Table 1. Write Configuration (D15, D14 = 1, 1)