19-1573; Rev 0; 10/99
3V Dual RS-232 Transceiver with
LCD Supply and Contrast Controller
General Description
The MAX3325 integrates a two-transmitter, two-receiver
RS-232 transceiver with an LCD supply plus tempera-
ture-compensated contrast control. It is intended for
small 3V instruments requiring a 5V supply for either
logic or an LCD display, an adjustable bias signal for
contrast, LCD temperature compensation, and an
RS-232 interface for serial communications.
The 5V supply is a regulated charge pump followed by
a low-dropout (LDO) linear regulator capable of supply-
ing 11mA for the 5V LCD power.
The MAX3325 has an internal 6-bit digital-to-analog
converter (DAC) providing 64 contrast levels, plus an
internal temperature sensor that compensates the
LCD’s contrast for changes in ambient temperature.
The LCD contrast can be designed for any voltage
range from -5V to +2V.
The MAX3325’s 250kbps RS-232 transceiver meets all
EIA-232E specifications with input voltages from +3.0V
to +3.6V. Both the RS-232 section and the LCD supply
circuitry can be independently placed in shutdown, tai-
loring power consumption for battery-powered equip-
ment. The MAX3325 is available in 28-pin SSOP and
narrow DIP packages.
Features
o
+3.0V to +3.6V Single-Supply Operation
o
Provides 5.0V Regulated Output at 11mA in
3V Systems
o
6-Bit DAC with Up/Down Interface for LCD
Contrast Adjustment
o
Selectable Positive or Negative LCD Bias
o
Meets EIA-232E Specifications at 250kbps—
Guaranteed
o
1µA Shutdown Mode
o
Uses Small 0.22µF Capacitors—No Inductors
Required
o
Temperature Sensor for LCD Contrast
Compensation
o
Simple, Flexible Design Procedure for a Broad
Range of LCD Displays
MAX3325
Ordering Information
PART
MAX3325CAI
MAX3325CNI
MAX3325EAI
MAX3325ENI
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 Narrow Plastic DIP
28 SSOP
28 Narrow Plastic DIP
Applications
PDAs and Palmtop Computers
Handy Terminals
GPS Receivers
Hand-Held Medical Equipment
Industrial Test Equipment
C2+ 1
C2- 2
V- 3
R2IN 4
R1IN 5
R1OUT 6
R2OUT 7
V
L
8
LCD 9
TEMP 10
REF- 11
FB 12
REF+ 13
DAC 14
Pin Configuration
TOP VIEW
28 C1+
27 V+
26 V
DD
25 GND
24 C1-
MAX3325
23 REG
22 T1OUT
21 T2OUT
20 T1IN
19 T2IN
18 SD232
17 SDLCD
16 DOWN
15 UP
Typical Operating Circuit appears at end of data sheet.
SSOP/DIP
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
3V Dual RS-232 Transceiver with
LCD Supply and Contrast Controller
MAX3325
ABSOLUTE MAXIMUM RATINGS
V
DD
, V
L
to GND ........................................................-0.3V to +6V
LCD, REF-, TEMP to GND .............................-6V to (V
DD
+ 0.3V)
V+ to GND (Note 1) ..................................................-0.3V to +7V
V- to GND (Note 1) ...................................................+0.3V to -7V
V+ to |V-| (Note 1) ................................................................+13V
REF+, FB, R_OUT to GND ............................-0.3V to (V
L
+ 0.3V)
Input Voltages
T_OUT,
SDLCD, SD232, UP, DOWN
to GND.......-0.3V to +6V
R_IN to GND ....................................................................±25V
Output Voltages
T_OUT to GND.................................................................±13V
R_OUT to GND..........................................-0.3V to (V
L
+ 0.3V)
REG to GND .........................................................-0.3V to +6V
Short-Circuit Duration (T_OUT, REF+, REF-) .............Continuous
Continuous Output Current
REG.................................................................................75mA
LCD .................................................................................40mA
Continuous Power Dissipation
28-Pin SSOP (derate 9.52mW/°C above +70°C) .........762mW
28-Pin NDIP (derate 14.3mW/°C above +70°C) ........1143mW
Operating Temperature Range
MAX3325C_I .......................................................0°C to +70°C
MAX3325E_I ....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1:
V+ and V- can have maximum magnitudes of +7V, but their absolute difference cannot exceed 13V.
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.
ELECTRICAL CHARACTERISTICS
(V
DD
= +3.0V to +3.6V, V
L
= +3.3V, circuit and components of Figure 1, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values
are at V
DD
= +3.3V, T
A
= +25°C.)
PARAMETER
DC CHARACTERISTICS
V
DD
Supply Current
V
L
Supply Current
V
DD
Shutdown Supply Current
No load, V
DD
= V
L
= 3.3V, T
A
= +25°C
No load, V
DD
= V
L
= 3.3V, T
A
= +25°C
SD232, SDLCD
= GND; all input pins = GND or V
DD
;
V
DD
= V
L
= 3.3V; T
A
= +25°C
Guaranteed monotonic
No load
No load
0 < V
DAC
< V
REF
+, I
DAC
≤
10µA
T
A
= +25°C
I
TEMP
< 22µA
1.13
-15
35
2
0.5
0.5
4
10
10
mA
µA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL-TO-ANALOG CONVERTER
Resolution
Full-Scale Voltage
Zero-Scale Voltage
Output Impedance
TEMPERATURE SENSOR
TEMP Output
TEMP Voltage Temperature
Coefficient
POSITIVE LINEAR REGULATOR
1 transmitter loaded with
5kΩ, T
A
= +25°C
3V < V
DD
< 3.6V
V
CC
≥
3.15V, I
REG
= 0 to
11mA
V
CC
≥
3.0V, I
REG
= 0 to
7mA
4.7
5
5
6
50
-20
V
FB
= 0, CMOS input
V
LCD
= -4.0V, load = 0 to -3mA
-10
0
0
20
20
10
50
mV
mA
mV
nA
mV
5.3
V
-3.2
-18
V
mV/°C
6
1.2
0
50
1.27
10
65
Bits
V
mV
kΩ
REG Output Voltage
Line Regulation
Short-Circuit Current
NEGATIVE LINEAR REGULATOR—LCD BIAS
Feedback Regulation Point
Input Leakage Current (Note 2)
LCD Load Regulation (Note 3)
2
_______________________________________________________________________________________
3V Dual RS-232 Transceiver with
LCD Supply and Contrast Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +3.0V to +3.6V, V
L
= +3.3V, circuit and components of Figure 1, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values
are at V
DD
= +3.3V, T
A
= +25°C.)
PARAMETER
LCD Line Regulation
LCD Adjustment Range
POSITIVE REFERENCE VOLTAGE
Output Voltage
Load Regulation
Short-Circuit Current
NEGATIVE REFERENCE VOLTAGE
Output Voltage
Load Regulation
Short-Circuit Current
LOGIC INPUTS
(SD232,
SDLCD,
T1IN, T2IN,
UP, DOWN)
Logic Threshold High
Logic Threshold Low
Input Current
RECEIVER OUTPUTS
Output Voltage Low
Output Voltage High
RECEIVER INPUTS
Input Voltage Range
Input Threshold Low
Input Threshold High
Input Hysteresis
Input Resistance
TRANSMITTER OUTPUTS
Output Voltage Swing
Output Resistance
Short-Circuit Current
Output Leakage Current
V
DD
= 0 or 3V to 3.6V, V
OUT
= ±12V, transmitters
disabled
All outputs loaded with 3kΩ to ground
V
DD
= V
L
= V+ = V- = 0, V
OUT
= ±2V
±5
300
±5.4
10M
±35
±60
±25
V
Ω
mA
µA
-15V < V
R_IN
< +15V, T
A
= +25°C
3
T
A
= +25°C, V
DD
= 3.3V
T
A
= +25°C, V
DD
= 3.3V
0.3
5
7
-25
0.6
2.4
+25
V
V
V
V
kΩ
I
SINK
= 1.6mA
I
SOURCE
= 1.0mA
0.8
·
V
L
0.4
V
V
V
IN
= GND or V
DD
-1
2
0.8
1
V
V
µA
No load
Load = 0 to 50µA (sinking current)
-1.14
-1.21
35
0.125
-1.28
V
mV
mA
R
REF
+ = 10kΩ
Load = 12µA to 62µA (sourcing current)
1.16
1.21
4
5
1.26
V
mV
mA
Load = -3mA
CONDITIONS
3V < V
DD
< 3.6V, V
LCD
= -4.0V
-5
MIN
TYP
10
+2
MAX
UNITS
mV
V
MAX3325
_______________________________________________________________________________________
3
3V Dual RS-232 Transceiver with
LCD Supply and Contrast Controller
MAX3325
TIMING CHARACTERISTICS
(V
DD
= +3.0V to +3.6V, V
L
= +3.3V, circuit and components of Figure 1, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values
are at V
DD
= +3.3V, T
A
= +25°C.)
PARAMETER
Maximum Data Rate
Receiver Propagation Delay
Receiver Skew
Transmitter Skew
Transition-Region Slew Rate
t
PHL
t
PLH
| t
PLH
- t
PHL
|
| t
PLH
- t
PHL
|
V
DD
= 3.3V, T
A
= +25°C, R
L
= 3kΩ to
7kΩ, C
L
= 150pF to 1000pF, measured
from +3V to -3V or -3V to +3V
6
SYMBOL
CONDITIONS
R
L
= 3kΩ, C
L
= 1000pF, one transmitter
switching
Receiver input to receiver output,
C
L
= 150pF
MIN
250
300
300
300
200
30
TYP
MAX
UNITS
kbps
ns
ns
ns
V/µs
Note 2:
Guaranteed by design and not production tested.
Note 3:
No load on REG or transmitter outputs.
Typical Operating Characteristics
(V
DD
= V
L
= +3.3V, circuit and components of Figure 1, all transmitters loaded with 3kΩ, T
A
= +25°C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CAPACITANCE
MAX3325toc01
SLEW RATE vs. LOAD CAPACITANCE
MAX3325toc02
SUPPLY CURRENT vs. LOAD
CAPACITANCE (T1 = 20kbps)
MAX3325toc03
TRANSMITTER OUTPUT VOLTAGE (V)
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
0
14
12
SLEW RATE (V/µs)
10
8
6
4
50
V
OUT+
T1 TRANSMITTING AT 250kbps
T2 TRANSMITTING AT 15.6kbps
40
SUPPLY CURRENT (mA)
T2 = 250kbps
30
T2 = 120kbps
20
T2 = 20kbps
10
V
OUT-
1000
2000
3000
4000
5000
2
0
0
FOR DATA RATES
UP TO 250kbps
1000
2000
3000
4000
5000
0
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
4
_______________________________________________________________________________________
3V Dual RS-232 Transceiver with
LCD Supply and Contrast Controller
Typical Operating Characteristics (continued)
(V
DD
= V
L
= +3.3V, circuit and components of Figure 1, all transmitters loaded with 3kΩ and C
L
, T
A
= +25°C, unless otherwise noted.)
MAX3325
TRANSMITTER OUTPUTS EXITING
SHUTDOWN OR POWERING UP
MAX3325toc04
LOOPBACK WAVEFORMS AT 120kbps
MAX3325toc05
LOOPBACK WAVEFORMS AT 250kbps
MAX3325toc06
5V/div
0
SD232
T2OUT
T1IN
5V/div
T1IN
5V/div
2V/div
0
T1OUT/
R1IN
5V/div
T1OUT/
R1IN
5V/div
V
CC
= 3.3V
C1–C4 = 0.1µF
C
L
= 2500pF
40µs/div
T1OUT
R1OUT
5V/div
R1OUT
5V/div
C
L
= 1000pF
2µs/div
C
L
= 1000pF
1µs/div
V
REG
vs. LOAD CURRENT
MAX3325toc07
V
REG
vs. LOAD CURRENT
AND TEMPERATURE
T
A
= +25°C
T
A
= -40°C
MAX3325toc08
TEMP OUTPUT VOLTAGE
vs. TEMPERATURE
MAX3325toc09
6
V
DD
= +3.6V
5
4
V
REG
(V)
3
2
1
0
0
10
20
LOAD CURRENT (mA)
30
V
DD
= +3V
6
5
4
V
REG
(V)
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
-4.5
V
DD
= +3.3V
3
2
1
0
T
A
= +85°C
TEMP OUTPUT VOLTAGE (V)
40
0
10
20
LOAD CURRENT (mA)
30
40
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
