Datasheet
ISL4270E
QFN Packaged, ±15kV ESD Protected, +3V to +5.5V, 300nA, 250kbps, RS-232
Transceivers with Enhanced Automatic Powerdown and a Separate Logic Supply
The ISL4270E is a 3.0V to 5.5V powered RS-232
transceiver that meets ElA/TIA-232 and V.28/V.24
specifications, even at VCC = 3.0V. It provides ±15kV
ESD protection (IEC61000-4-2 Air Gap and Human
Body Model) on transmitter outputs and receiver
inputs (RS-232 pins). Targeted applications are
notebook and laptop computers where the low
operational power consumption and even lower
standby power consumption is critical. Efficient
on-chip charge-pumps coupled with manual and
enhanced automatic powerdown functions reduce the
standby supply current to a 300nA trickle. The
5mmx5mm Quad Flat No-Lead (QFN) packaging and
the use of small, low value capacitors ensure board
space savings. Data rates greater than 250kbps are
ensured at worst case load conditions.
The ISL4270E features a VL pin that adjusts the logic
pin output levels and input thresholds to values
compatible with the VCC powering the external logic
(for example, a UART).
This device includes an enhanced automatic
powerdown function that powers down the on-chip
power-supply and driver circuits. Automatic
powerdown occurs when all receiver and transmitter
inputs detect no signal transitions for a period of
30 seconds. The ISL4270E automatically powers
back up whenever it senses a transition on any
transmitter or receiver input.
Table 1 summarizes the features of the ISL4270E.
Application Note AN9863 summarizes the features of
each device comprising the 3V RS-232 family.
Features
• Available in near chip scale QFN (5mmx5mm)
package
• VL supply pin for compatibility with mixed voltage
systems
• ESD protection for RS-232 I/O pins to 15kV
(IEC61000)
• Manual and enhanced automatic powerdown
features
• Meets EIA/TIA-232 and V.28/V.24 specifications
at 3V
• On-chip charge pumps require only four external
0.1µF capacitors
• Receivers stay active in powerdown
• Very low supply current: 300µA
• Guaranteed minimum data rate: 50kbps
• Wide power supply range: single +3V to +5.5V
• Low supply current in powerdown state: 300nA
• Pb-free (RoHS compliant)
Applications
• Any system requiring RS-232 communication ports
○ Battery powered, hand-held, and portable
equipment
○ Industrial laptops, Palmtops, and PDAs
○ Digital cameras
Related Literature
For a full list of related documents, visit our website:
• ISL4270E device page
Table 1.
Summary of Features
Part Number
No. of
Tx.
No. of
Rx.
Data Rate
(kbps)
Rx. Enable
Function?
VL Logic
Supply Pin?
Manual
Powerdown?
Enhanced Automatic
Powerdown Function?
ISL4270E
3
3
250
No
Yes
Yes
Yes
FN6041 Rev.3.00
Apr 26, 2019
Page 1 of 23
ISL4270E
Contents
1.
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
1.2
1.3
1.4
2.
Typical Operating Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pinout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
3
4
4
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1
2.2
2.3
2.4
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
5
5
6
3.
Typical Performance Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.
Application Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1
4.1.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
5.
Charge Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Charge Pump Abs Max Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Power Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Powerdown Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Software Controlled (Manual) Powerdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enhanced Automatic Powerdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Emulating Standard Automatic Powerdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hybrid Automatic Powerdown Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VL Logic Supply Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INVALID Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Decoupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmitter Outputs when Exiting Powerdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Data Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interconnection with 3V and 5V Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
10
11
11
12
12
12
13
14
15
15
15
16
16
16
17
18
±15kV ESD Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.1
Human Body Model (HBM) Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2
IEC61000-4-2 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.1
Air-Gap Discharge Test Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.2
Contact Discharge Test Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
19
19
19
6.
Die Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.
Package Outline Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
FN6041 Rev.3.00
Apr 26, 2019
Page 2 of 23
ISL4270E
1.
1.1
1. Overview
Overview
Typical Operating Circuit
+3.3V
+
0.1µF
29
C1
0.1µF
+
C2
0.1µF
+
31
2
3
27
C1+
VCC
30
V+
C1C2+
4
V-
C2T1
5
23
T1IN
T2IN
T2
6
22
T3
10
21
T3IN
TTL/CMOS
Logic Levels
R1
14
20
R1OUT
+
C3
0.1µF
C4
0.1µF
+
T1OUT
T2OUT
RS-232
Levels
T3OUT
R1IN
5kΩ
R2OUT
R2
13
19
R2IN
5kΩ
R3
12
18
R3OUT
RS-232
Levels
R3IN
5kΩ
Logic VCC
0.1µF
15
+
11
28
VCC
To Power
Control Logic
7
VL
FORCEON
FORCEOFF
INVALID
GND
26
1.2
Ordering Information
Part Number
(Notes 2, 3)
Part Marking
Temp. Range (°C)
Tape and Reel
(Units) (Note 1)
Pkg.
Dwg. #
Package
ISL4270EIRZ
ISL4270 EIRZ
-40 to +85
-
32 Ld QFN (Pb-free)
L32.5x5B
ISL4270EIRZ-T
ISL4270 EIRZ
-40 to +85
6k
32 Ld QFN (Pb-free)
L32.5x5B
Notes:
1. See TB347 for details about reel specifications.
2. These Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and NiPdAu-Ag
plate - e4 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Pb-free products
are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), see the ISL4270E device page. For more information about MSL, see TB363.
FN6041 Rev.3.00
Apr 26, 2019
Page 3 of 23
ISL4270E
1.3
1. Overview
Pinout
1.4
NC
C1-
V+
C1+
FORCEOFF
VCC
GND
NC
32 Ld 5x5 QFN Package
Top View
32
31
30
29
28
27
26
25
NC
1
24
NC
C2+
2
23
T1OUT
C2-
3
22
T2OUT
V-
4
21
T3OUT
20
R1IN
PD
18
R3IN
NC
8
17
NC
9
10
11
12
13
14
15
16
NC
7
VL
INVALID
R1OUT
R2IN
R2OUT
19
R3OUT
6
FORCEON
T2IN
T3IN
5
NC
T1IN
Pin Descriptions
Pin Name
Description
NC
No connect.
C2+
External capacitor (voltage inverter) is connected to this lead.
C2-
External capacitor (voltage inverter) is connected to this lead.
V-
Internally generated negative transmitter supply (-5.5V).
TIN
TTL/CMOS compatible transmitter inputs. The switching point is a function of the VL voltage.
INVALID
Active low output that indicates if no valid RS-232 levels are present on any receiver input. Swings between GND and VL.
FORCEON
Active high input to override automatic powerdown circuitry, which keeps transmitters active (FORCEOFF must be high).
The switching point is a function of the VL voltage.
ROUT
TTL/CMOS level receiver outputs. Swings between GND and VL.
VL
Logic-level supply. All TTL/CMOS inputs and outputs are powered by this supply.
RIN
±15kV ESD protected, RS-232 compatible receiver inputs.
TOUT
±15kV ESD protected, RS-232 level (nominally ±5.5V) transmitter outputs.
GND
Ground connection. This is also the potential of the thermal pad (PD).
VCC
System power supply input (3.0V to 5.5V).
FORCEOFF
C1+
Active low to shut down transmitters and on-chip power supply. This overrides any automatic circuitry and FORCEON (see
Table 5 on page 12). The switching point is a function of the VL voltage.
External capacitor (voltage doubler) is connected to this lead.
V+
Internally generated positive transmitter supply (+5.5V).
C1-
External capacitor (voltage doubler) is connected to this lead.
PD
Exposed thermal pad. Connect to GND.
FN6041 Rev.3.00
Apr 26, 2019
Page 4 of 23
ISL4270E
2.
2. Specifications
Specifications
2.1
Absolute Maximum Ratings
Minimum
Maximum
Unit
VCC to Ground
Parameter
-0.3
6
V
VL to Ground
-0.3
7
V
V+ to Ground
-0.3
7
V
V- to Ground
+0.3
-7
V
14
14
V
-0.3
6
V
±25
V
±13.2
V
VL +0.3
V
Continuous
-
V+ to VInput Voltages
TIN, FORCEON, FORCEOFF
RIN
Output Voltages
TOUT
ROUT, INVALID
-0.3
Short Circuit Duration
TOUT
See “ESD Performance” on page 7
ESD Rating
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions can adversely
impact product reliability and result in failures not covered by warranty.
2.2
Thermal Information
Thermal Resistance (Typical)
θJA (°C/W)
θJC (°C/W)
30
2.2
32 Ld QFN Package (Notes 4, 5)
Notes:
4. θJA is measured in free air with the component mounted on a high-effective thermal conductivity test board with “direct attach” features.
See TB379 and TB389.
5. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside..
Parameter
Minimum
Maximum Junction Temperature
Maximum Storage Temperature Range
-65
Pb-Free Reflow Profile
2.3
Maximum
Unit
+150
°C
+150
°C
see TB493
Recommended Operating Conditions
Parameter
Temperature Range
FN6041 Rev.3.00
Apr 26, 2019
Minimum
Maximum
Unit
-40
+85
°C
Page 5 of 23
ISL4270E
2.4
2. Specifications
Electrical Specifications
Test conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1µF, VL = VCC; unless otherwise specified. Typicals are at TA = 25°C, VCC = VL = 3.3V
Parameter
Test Conditions
Temp (°C)
Min
Note 7
Typ
Max
Note 7
Unit
DC Characteristics
Supply Current, Automatic
Powerdown
All RIN Open, FORCEON = GND, FORCEOFF = VCC
25
-
0.3
5
µA
Supply Current, Powerdown
FORCEOFF = GND
25
-
0.3
5
µA
Supply Current,
Automatic Powerdown
Disabled
All Outputs Unloaded,
FORCEON = FORCEOFF = VCC, VCC = 3.15V
25
-
0.3
1
mA
TIN, FORCEON, FORCEOFF
VL = 3.3V or 5V
Full
-
-
0.8
V
VL = 2.5V
Full
-
-
0.6
V
VL = 5V
Full
2.4
-
-
V
VL = 3.3V
Full
2.0
-
-
V
VL = 2.5V
Full
1.4
-
-
V
VL = 1.8V
25
-
0.9
-
V
25
-
0.5
-
V
TIN, FORCEON, FORCEOFF
Full
-
±0.01
±1.0
µA
Output Voltage Low
IOUT = 1.6mA
Full
-
-
0.4
V
Output Voltage High
IOUT = -1.0mA
Full
VL - 0.6
VL - 0.1
-
V
Full
-25
-
25
V
VCC = VL = 5.0V
25
0.8
1.5
-
V
VCC = VL = 3.3V
25
0.6
1.2
-
V
VCC = VL = 5.0V
25
-
1.8
2.4
V
VCC = VL = 3.3V
25
-
1.5
2.4
V
Input Hysteresis
25
-
0.5
-
V
Input Resistance
25
3
5
7
kΩ
Logic and Transmitter Inputs
Input Logic Threshold Low
Input Logic Threshold High
TIN, FORCEON, FORCEOFF
Transmitter Input Hysteresis
Input Leakage Current
Receiver Outputs
Receiver Inputs
Input Voltage Range
Input Threshold Low
Input Threshold High
Transmitter Outputs
Output Voltage Swing
All Transmitter Outputs Loaded with 3kΩ to Ground
Full
5.0
5.4
-
V
Output Resistance
VCC = V+ = V- = 0V, Transmitter Output = ±2V
Full
300
10M
-
Ω
Output Short-Circuit Current
VOUT = 0V
Full
-
35
60
mA
Output Leakage Current
VOUT = ±12V, VCC = 0V or 3V to 5.5V
Automatic Powerdown or FORCEOFF = GND
Full
-
-
25
µA
Enhanced Automatic Powerdown (FORCEON = GND, FORCEOFF = VCC)
Receiver Input Thresholds to
INVALID High
See Figure 11
Full
-2.7
-
2.7
V
Receiver Input Thresholds to
INVALID Low
See Figure 11
Full
-0.3
-
0.3
V
INVALID Output Voltage Low
IOUT = 1.6mA
Full
-
-
0.4
V
INVALID Output Voltage High
IOUT = -1.0mA
Full
VL - 0.6
-
-
V
Receiver Positive or Negative
Threshold to INVALID High
Delay (tINVH)
See Figure 13
25
-
1
-
µs
FN6041 Rev.3.00
Apr 26, 2019
Page 6 of 23
ISL4270E
2. Specifications
Test conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1µF, VL = VCC; unless otherwise specified. Typicals are at TA = 25°C, VCC = VL = 3.3V
Parameter
Test Conditions
Temp (°C)
Min
Note 7
Typ
Max
Note 7
Unit
Receiver Positive or Negative
Threshold to INVALID Low
Delay (tINVL)
See Figure 13
25
-
30
-
µs
Receiver or Transmitter Edge
to Transmitters Enabled
Delay (tWU)
Note 6, see Figure 13
25
-
100
-
µs
Receiver or Transmitter Edge
to Transmitters Disabled
Delay (tAUTOPWDN)
Note 6, see Figure 13
Full
15
30
60
s
Timing Characteristics
Maximum Data Rate
RL = 3kΩCL = 1000pF, One Transmitter Switching
Full
250
500
-
kbps
Receiver Propagation Delay
Receiver Input to Receiver
Output, CL = 150pF
tPHL
25
-
0.15
-
µs
tPLH
25
-
0.15
-
µs
TX | VOUT | ≥ 3.7V
25
-
100
-
µs
Transmitter Skew
tPHL - tPLH
25
-
100
-
ns
Receiver Skew
tPHL - tPLH
25
-
50
-
ns
Transition Region Slew Rate
VCC = 3.3V,
RL = 3kΩto 7kΩ
Measured From 3V to -3V or
-3V to 3V
CL = 150pF to 1000pF
25
6
18
30
V/µs
CL = 150pF to 2500pF
25
4
13
30
V/µs
Human Body Model
25
-
±15
-
kV
IEC61000-4-2 Air Gap Discharge
25
-
±15
-
kV
IEC61000-4-2 Contact Discharge
25
-
±8
-
kV
Time to Exit Powerdown
ESD Performance
RS-232 Pins (TOUT, RIN)
Notes:
6. An edge is defined as a transition through the transmitter or receiver input thresholds.
7. Parameters with Min and/or Max limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by
characterization and are not production tested.
FN6041 Rev.3.00
Apr 26, 2019
Page 7 of 23
ISL4270E
3.
3. Typical Performance Curves
Typical Performance Curves
VCC = VL = 3.3V, TA = 25°C
30
6.0
VOUT+
25
2.0
Slew Rate (V/µs)
Transmitter Output Voltage (V)
4.0
1 Transmitter at 250kbps
Other Transmitters at 30kbps
0
-2.0
-6.0
0
1000
2000
3000
4000
+Slew
15
-Slew
10
VOUT -
-4.0
20
5
5000
0
1000
3000
4000
5000
Figure 2. Slew Rate vs Load Capacitance
Figure 1. Transmitter Output Voltage vs Load
Capacitance
45
3.5
40
No Load
All Outputs Static
3.0
250kbps
35
2.5
Supply Current (mA)
Supply Current (mA)
2000
Load Capacitance (pF)
Load Capacitance (pF)
30
120kbps
25
20
20kbps
15
2.0
1.5
1.0
0.5
10
0
1000
2000
3000
4000
5000
Load Capacitance (pF)
Figure 3. Supply Current vs Load Capacitance When
Transmitting Data
FN6041 Rev.3.00
Apr 26, 2019
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Supply Voltage (V)
Figure 4. Supply Current vs Supply Voltage
Page 8 of 23
ISL4270E
3. Typical Performance Curves
VCC = VL = 3.3V, TA = 25°C (Continued)
10m
1m
No Load
All Outputs Static
VCC = 3.3V
100µ
IL (A)
10µ
VL ≤ VCC
VL > VCC
1µ
100n
10n
1n
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
VL (V)
Figure 5. VL Supply Current vs VL Voltage
FN6041 Rev.3.00
Apr 26, 2019
Page 9 of 23
ISL4270E
4.
4. Application Information
Application Information
The ISL4270E operates from a single +3V to +5.5V supply, ensures a 250kbps minimum data rate, requires only
four small external 0.1µF capacitors, features low power consumption, and meets all ElA RS-232C and V.28
specifications.
4.1
Charge Pump
The ISL4270E uses regulated on-chip dual charge pumps as voltage doublers, and voltage inverters to generate
±5.5V transmitter supplies from a VCC supply as low as 3.0V. These voltages allow the ISL4270E to maintain
RS-232 compliant output levels over the ±10% tolerance range of 3.3V powered systems. The efficient on-chip
power supplies require only four small, external 0.1µF capacitors for the voltage doubler and inverter functions
over the full VCC range; other capacitor combinations can be used as shown in Table 6 on page 16. The charge
pumps operate discontinuously (turning off as soon as the V+ and V- supplies are pumped up to the nominal
values) and provide significant power savings.
4.1.1 Charge Pump Abs Max Ratings
The ISL4270E is fully characterized for 3.0V to 3.6V operation and at critical points for 4.5V to 5.5V operation.
Furthermore, load conditions were favorable using static logic states only.
The specified maximum values for V+ and V- are +7V and -7V, respectively. These limits apply for VCC values set
to 3.0V and 3.6V (see Table 2). For VCC values set to 4.5V and 5.5V, the maximum values for V+ and
V- can approach +9V and -7V, respectively (Table 3 on page 11). The breakdown characteristics for V+ and Vwere measured with ±13V.
Table 2.
V+ and V- Values for VCC = 3.0V to 3.6V
C1 (μF)
C2, C3, C4 (μF)
Load
T1IN
(Logic State)
0.1
0.1
Open
H
3kΩ // 1000pF
0.047
0.33
Open
3kΩ // 1000pF
1
1
Open
3kΩ // 1000pF
FN6041 Rev.3.00
Apr 26, 2019
V+ (V)
V- (V)
VCC = 3.0V
VCC = 3.6V
VCC = 3.0V
VCC = 3.6V
5.80
6.56
-5.60
-5.88
L
5.80
6.56
-5.60
-5.88
2.4kbps
5.80
6.56
-5.60
-5.88
H
5.88
6.60
-5.56
-5.92
L
5.76
6.36
-5.56
-5.76
2.4kbps
6.00
6.64
-5.64
-5.96
H
5.68
6.00
-5.60
-5.60
L
5.68
6.00
-5.60
-5.60
2.4kbps
5.68
6.00
-5.60
-5.60
H
5.76
6.08
-5.64
-5.64
L
5.68
6.04
-5.60
-5.60
2.4kbps
5.84
6.16
-5.64
-5.72
H
5.88
6.24
-5.60
-5.60
L
5.88
6.28
-5.60
-5.64
2.4kbps
5.80
6.20
-5.60
-5.60
H
5.88
6.44
-5.64
-5.72
L
5.88
6.04
-5.64
-5.64
2.4kbps
5.92
6.40
-5.64
-5.64
Page 10 of 23
ISL4270E
4. Application Information
Table 3.
V+ and V- Values for VCC = 4.5V to 5.5V
C1 (μF)
C2, C3, C4 (μF)
Load
T1IN
(Logic State)
0.1
0.1
Open
H
7.44
8.48
-6.16
-6.40
L
7.44
8.48
-6.16
-6.44
2.4kbps
7.44
8.48
-6.17
-6.44
H
7.76
8.88
-6.36
-6.72
3kΩ // 1000pF
0.047
0.33
Open
3kΩ // 1000pF
1
1
Open
3kΩ // 1000pF
V+ (V)
VCC = 4.5V
V- (V)
VCC = 5.5V
VCC = 4.5V
VCC = 5.5V
L
7.08
8.00
-5.76
-5.76
2.4kbps
7.76
8.84
-6.40
-6.64
H
6.44
6.88
-5.80
-5.88
L
6.48
6.88
-5.84
-5.88
2.4kbps
6.44
6.88
-5.80
-5.88
H
6.64
7.28
-5.92
-6.04
L
6.24
6.60
-5.52
-5.52
2.4kbps
6.72
7.16
-5.92
-5.96
H
6.84
7.60
-5.76
-5.76
L
6.88
7.60
-5.76
-5.76
2.4kbps
6.92
7.56
-5.72
-5.76
H
7.28
8.16
-5.80
-5.92
L
6.44
6.84
-5.64
-6.84
2.4kbps
7.08
7.76
-5.80
-5.80
The resulting new maximum voltages at V+ and V- are listed in Table 4.
Table 4.
4.2
New Measured Withstanding Voltages
V+, V- to Ground
±13V
V+ to V-
20V
Transmitters
The transmitters are proprietary, low dropout, inverting drivers that translate TTL/CMOS inputs to EIA/TIA-232
output levels. These transmitters are coupled with the on-chip ±5.5V supplies to deliver true RS-232 levels across
a wide range of single supply system voltages.
All transmitter outputs disable and assume a high impedance state when the device enters the powerdown mode
(see Table 5 on page 12). The outputs can be driven to ±12V when disabled.
All devices ensure a 250kbps data rate for full load conditions (3kΩ and 1000pF), VCC ≥ 3.0V, with one transmitter
operating at full speed. Under more typical conditions of VCC ≥ 3.3V, RL = 3kΩ, and CL = 250pF, one transmitter
easily operates at 1.25Mbps.
The transmitter input threshold is set by the voltage applied to the VL supply pin. Transmitter inputs float if they are
unconnected (there are no pull-up resistors), and may cause ICC increases. Connect unused inputs to GND for
the best performance.
4.3
Receivers
The ISL4270E contains standard inverting receivers that convert RS-232 signals to CMOS output levels and
accept inputs up to ±25V while presenting the required 3kΩ to 7kΩ input impedance (see Figure 6 on page 12)
even if the power is off (VCC = 0V). The receivers’ Schmitt trigger input stage uses hysteresis to increase noise
immunity and decrease errors due to slow input signal transitions. Receiver outputs swing from GND to VL and do
not tristate in powerdown (see Table 5).
FN6041 Rev.3.00
Apr 26, 2019
Page 11 of 23
ISL4270E
4. Application Information
VL
RXOUT
RXIN
-25V ≤ VRIN ≤ +25V
5kΩ
GND ≤ VROUT ≤ VL
GND
Figure 6. Receiver Connections
4.4
Low Power Operation
The 3V ISL4270E requires a nominal supply current of 0.3mA, even at VCC = 5.5V during normal operation (not in
powerdown mode). This supply current is considerably less than the 11mA current required by comparable
5V RS-232 devices, which allows you to reduce system power by replacing the old device with the ISL4270E in
new designs.
4.5
Powerdown Functionality
The already low current requirement drops significantly when the device enters powerdown mode. In powerdown,
supply current drops to 1µA because the on-chip charge pump turns off (V+ collapses to VCC, V- collapses to
GND), and the transmitter outputs tristate. This micro-power mode makes the ISL4270E ideal for battery powered
and portable applications.
4.6
Software Controlled (Manual) Powerdown
The ISL4270E allows you to force the IC into the low power, standby state, and uses a two pin approach where
the FORCEON and FORCEOFF inputs determine the IC’s mode. For always enabled operation, FORCEON and
FORCEOFF are both strapped high. Under logic or software control, only the FORCEOFF input needs to be
driven to switch between active and powerdown modes. The FORCEON state is not critical because FORCEOFF
overrides FORCEON. However, if strictly manual control over powerdown is needed, you must strap FORCEON
high to disable the enhanced automatic powerdown circuitry.
Connecting FORCEOFF and FORCEON together disables the enhanced automatic powerdown feature and
enables them to function as a manual SHUTDOWN input (see Figure 7 on page 13).
With any of the above control schemes, the time required to exit powerdown and resume transmission is only
100µs.
When using both manual and enhanced automatic powerdown (FORCEON = 0), the ISL4270E does not power
up from manual powerdown until both FORCEOFF and FORCEON are driven high, or until a transition occurs on
a receiver or transmitter input. Figure 8 on page 13 shows a circuit for ensuring that the ISL4270E powers up as
soon as FORCEOFF switches high. The rising edge of the Master Powerdown signal forces the device to power
up and the ISL4270E returns to enhanced automatic powerdown mode an RC time constant after this rising edge.
The time constant is not critical because the ISL4270E remains powered up for 30 seconds after the FORCEON
falling edge, even if there are no signal transitions. This gives slow-to-wake systems (for example, a mouse)
plenty of time to start transmitting, and as long as it starts transmitting within 30 seconds both systems remain
enabled.
Table 5.
Powerdown Logic Truth Table
Rcvr or Xmtr
Edge Within 30
Sec?
FORCEOFF
Input
FORCEO
N
Input
Transmitter
Outputs
Receiver
Outputs
RS-232 Level
Present at
Receiver Input?
INVALID
Output
No
H
H
Active
Active
No
L
No
H
H
Active
Active
Yes
H
Yes
H
L
Active
Active
No
L
Yes
H
L
Active
Active
Yes
H
No
H
L
High-Z
Active
No
L
No
H
L
High-Z
Active
Yes
H
FN6041 Rev.3.00
Apr 26, 2019
Mode of Operation
Normal Operation (Enhanced
Auto Powerdown Disabled)
Normal Operation (Enhanced
Auto Powerdown Enabled)
Powerdown Due to Enhanced
Auto Powerdown Logic
Page 12 of 23
ISL4270E
Table 5.
4. Application Information
Powerdown Logic Truth Table
Rcvr or Xmtr
Edge Within 30
Sec?
FORCEOFF
Input
X
L
X
L
FORCEO
N
Input
RS-232 Level
Present at
Receiver Input?
INVALID
Output
Transmitter
Outputs
Receiver
Outputs
X
High-Z
Active
No
L
X
High-Z
Active
Yes
H
Mode of Operation
Manual Powerdown
INVALID Driving FORCEON and FORCEOFF (Emulates Automatic Powerdown)
X
Note 8
Note 8
Active
Active
Yes
H
Normal Operation
X
Note 8
Note 8
High-Z
Active
No
L
Forced Auto Powerdown
Note:
8. Input is connected to the INVALID output.
FORCEOFF, FORCEON
Power
Management
Logic
INVALID
I/O Chip
Power Supply
VL
ISL4270E
VCC
CPU
I/O
UART
Figure 7. Connections for Manual Powerdown
Power
Management
Unit
Master Powerdown Line
0.1µF
FORCEOFF
1MΩ
FORCEON
ISL4270E
Figure 8. Circuit to Ensure Immediate Power Up When Exiting Forced Powerdown
4.7
Enhanced Automatic Powerdown
Even greater power savings are available by using the enhanced automatic powerdown function. When the
enhanced powerdown logic determines that no transitions have occurred on any of the transmitter or receiver
inputs for 30 seconds, the charge pump and transmitters powerdown and reduce the supply current to 1µA. The
ISL4270E automatically powers back up whenever it detects a transition on one of these inputs. The automatic
powerdown feature provides additional system power savings without changes to the existing operating system.
FN6041 Rev.3.00
Apr 26, 2019
Page 13 of 23
ISL4270E
4. Application Information
Enhanced automatic powerdown operates when the FORCEON input is low and the FORCEOFF input is high.
Tying FORCEON high disables automatic powerdown, but manual powerdown is always available from the
overriding FORCEOFF input. Table 5 summarizes the enhanced automatic powerdown functionality.
Figure 9 shows the enhanced powerdown control logic. Note: When the ISL4270E enters powerdown (manually
or automatically), the 30 second timer remains timed out (set) and keeps the ISL4270E powered down until
FORCEON transitions high, or until a transition occurs on a receiver or transmitter input.
The INVALID output switches low whenever invalid levels have persisted on all of the receiver inputs for more
than 30µs (see Figure 13), but this has no direct effect on the state of the ISL4270E (see “Emulating Standard
Automatic Powerdown” on page 14 and “Capacitor Selection” on page 16 for methods of using INVALID to power
down the device).
The time to recover from automatic powerdown mode is typically 100µs.
FORCEOFF
T_IN
Edge
Detect
S
30s
Timer
R_IN
AUTOPWDN
R
Edge
Detect
FORCEON
Figure 9. Enhanced Automatic Powerdown Logic
FORCEOFF
FORCEON
Emulating Standard Automatic Powerdown
INVALID
4.8
ISL4270E
I/O
UART
CPU
Figure 10. Connections for Automatic Powerdown When
No Valid Receiver Signals are Present
If enhanced automatic powerdown is not required, you can implement the standard automatic powerdown feature
(mimics the function on the ICL3221E/23E/43E) by connecting the INVALID output to the FORCEON and
FORCEOFF inputs, as shown in Figure 10. After 30µs of invalid receiver levels, INVALID switches low and drives
the ISL4270E into a forced powerdown condition. INVALID switches high as soon as a receiver input senses a
valid RS-232 level and forces the ISL4270E to power on. See the “INVALID DRIVING FORCEON AND
FORCEOFF” section of Table 5 on page 12 for an operational summary. This operational mode is perfect for
handheld devices that communicate with another computer through a detachable cable. Detaching the cable
allows the internal receiver pull-down resistors to pull the inputs to GND (an invalid RS-232 level), which causes
the 30µs timer to time out and drive the IC into powerdown. Reconnecting the cable restores valid levels and
causes the IC to power back up.
FN6041 Rev.3.00
Apr 26, 2019
Page 14 of 23
ISL4270E
4.9
4. Application Information
Hybrid Automatic Powerdown Options
For devices that communicate only through a detachable cable, you can connect INVALID to FORCEOFF (with
FORCEON = 0). While the cable is attached, INVALID and FORCEOFF remain high, so the enhanced automatic
powerdown logic powers down the RS-232 device whenever there is 30 seconds of inactivity on the receiver and
transmitter inputs. Detaching the cable allows the receiver inputs to drop to an invalid level (GND), so INVALID
switches low and forces the RS-232 device to power down. The ISL4270E remains powered down until the cable
is reconnected (INVALID = FORCEOFF = 1) and a transition occurs on a receiver or transmitter input (see
Figure 9 on page 14). For immediate power up when the cable is reattached, connect FORCEON to FORCEOFF
through a network similar to that shown in Figure 8 on page 13.
4.10
VL Logic Supply Input
Unlike other RS-232 interface devices where the CMOS outputs swing between 0V and VCC, the ISL4270E
features a separate logic supply input (VL; 1.8V to 5V, regardless of VCC) that sets VOH for the receiver and
INVALID outputs. Connecting VL to a host logic supply lower than VCC prevents the ISL4270E outputs from
forward biasing the input diodes of a logic device powered by that lower supply. Connecting VL to a logic supply
greater than VCC ensures that the receiver and INVALID output levels are compatible even with the CMOS input
VIH of AC, HC, and CD4000 devices. Note: The VL supply current increases to 100µA with VL = 5V and
VCC = 3.3V (see Figure 5 on page 9). VL also powers the transmitter and logic inputs and sets their switching
thresholds to levels compatible with the logic supply. The separate logic supply pin allows a great deal of flexibility
in interfacing to systems with different logic supplies. If logic translation is not required, connect VL to the
ISL4270E VCC pin.
4.11
INVALID Output
Table 5 on page 12 shows that the INVALID output always indicates whether 30µs have elapsed with invalid
RS-232 signals (see Figures 11 and 13) persisting on all of the receiver inputs. The indicator provides an easy
way to determine when the interface block should power down. Invalid receiver levels occur whenever the driving
peripheral’s outputs are shut off (powered down) or when the RS-232 interface cable is disconnected. If an
interface cable is disconnected and all the receiver inputs are floating (but pulled to GND by the internal receiver
pull down resistors), the INVALID logic detects the invalid levels and drives the output low. The power
management logic then uses this indicator to power down the interface block. Reconnecting the cable restores
valid levels at the receiver inputs, INVALID switches high, and the power management logic wakes up the
interface block. INVALID can also be used to indicate the DTR or RING INDICATOR signal as long as the other
receiver inputs are floating or driven to GND (as in the case of a powered down driver).
INVALID switches high 1µs after detecting a valid RS-232 level on a receiver input. INVALID operates in all
modes (forced or automatic powerdown, or forced on), so it is also useful for systems employing manual
powerdown circuitry.
2.7V
VALID RS-232 LEVEL - INVALID = 1
Indeterminate
0.3V
Invalid Level - INVALID = 0
-0.3V
Indeterminate
-2.7V
Valid RS-232 Level - INVALID = 1
Figure 11. Definition of Valid RS-232 Receiver Levels
FN6041 Rev.3.00
Apr 26, 2019
Page 15 of 23
ISL4270E
4.12
4. Application Information
Capacitor Selection
The ISL4270E charge-pumps require only 0.1µF capacitors for the full operational voltage range. Table 6 lists
other acceptable capacitor values for various supply voltage ranges. Do not use values smaller than those listed
in Table 6. Increasing the capacitor values (by a factor of 2) reduces ripple on the transmitter outputs and slightly
reduces power consumption.
Table 6.
Required Capacitor Values
VCC (V)
C1 (µF)
C2, C3, C4 (µF)
3.0 to 3.6
0.1
0.1
4.5 to 5.5
0.047
0.33
3.0 to 5.5
0.22
1
When using minimum required capacitor values, make sure that capacitor values do not degrade excessively with
temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance
(ESR) usually rises at low temperatures and influences the amount of ripple on V+ and V-.
4.13
Power Supply Decoupling
In most circumstances a 0.1µF bypass capacitor is adequate. In applications that are particularly sensitive to
power supply noise, decouple VCC to ground with a capacitor of the same value as the charge pump capacitor C1.
Connect the bypass capacitor as close as possible to the IC.
4.14
Transmitter Outputs when Exiting Powerdown
Figure 12 shows the response of two transmitter outputs when exiting powerdown mode. As the transmitter
outputs activate, they properly go to opposite RS-232 levels, with no glitching, ringing, or undesirable transients.
Each transmitter is loaded with 3kΩin parallel with 2500pF. Note: The transmitters enable only when the
magnitude of the supplies exceeds approximately 3V.
5V/Div
FORCEOFF
T1
2V/Div
T2
VCC = +3.3V
C1 - C4 = 0.1µF
Time (20µs/Div)
Figure 12. Transmitter Outputs When Exiting Powerdown
FN6041 Rev.3.00
Apr 26, 2019
Page 16 of 23
ISL4270E
4. Application Information
} Invalid
Region
Receiver
Inputs
Transmitter
Inputs
Transmitter
Outputs
tINVH
INVALID
Output
tINVL
tAUTOPWDN
tWU
tAUTOPWDN
tWU
V+
VCC
0
V-
Figure 13. Enhanced Automatic Powerdown and Invalid Timing Diagrams
4.15
High Data Rates
The ISL4270E maintains the RS-232 5V minimum transmitter output voltages even at high data rates. Figure 14
shows a transmitter loopback test circuit, and Figure 15 on page 18 shows the loopback test result at 120kbps.
For this test, all transmitters were simultaneously driving RS-232 loads in parallel with 1000pF at 120kbps.
Figure 16 on page 18 shows the loopback results for a single transmitter driving 1000pF and an RS-232 load at
250kbps. The static transmitters were also loaded with an RS-232 receiver.
VCC
+
0.1µF
+
C1
VCC
C1+
VL
V+
C1+
C2
ISL4270E
V-
C2+
C2TIN
ROUT
FORCEON
VCC
+
C3
C4
+
TOUT
RIN
1000pF
5k
FORCEOFF
Figure 14. Transmitter Loopback Test Circuit
FN6041 Rev.3.00
Apr 26, 2019
Page 17 of 23
ISL4270E
4. Application Information
5V/Div
T1IN
T1OUT
R1OUT
VCC = +3.3V
C1 - C4 = 0.1µF
5µs/Div
Figure 15. Loopback Test at 120kbps
5V/Div
T1IN
T1OUT
R1OUT
VCC = +3.3V
C1 - C4 = 0.1µF
2µs/Div
Figure 16. Loopback Test at 250kbps
4.16
Interconnection with 3V and 5V Logic
Standard 3.3V powered RS-232 devices interface well with 3V and 5V powered TTL compatible logic families
(such as ACT and HCT), but the logic outputs (for example, ROUTS) fail to reach the VIH level of 5V powered
CMOS families like HC, AC, and CD4000. The ISL4270E VL supply pin solves this problem. By connecting VL to
the same supply (1.8V to 5V) powering the logic device, the ISL4270E logic outputs swing from GND to the logic
VCC.
FN6041 Rev.3.00
Apr 26, 2019
Page 18 of 23
ISL4270E
5.
5. ±15kV ESD Protection
±15kV ESD Protection
All pins on the 3V interface devices include ESD protection structures, but the ISL4270E incorporates advanced
structures that allow the RS-232 pins (transmitter outputs and receiver inputs) to survive ESD events up to ±15kV.
The RS-232 pins are particularly vulnerable to ESD damage because they typically connect to an exposed port on
the exterior of the finished product. Touching the port pins or connecting a cable can cause an ESD event that
might destroy unprotected ICs. The ESD structures protect the device whether or not it is powered up, protect
without allowing any latchup mechanism to activate, and do not interfere with RS-232 signals as large as ±25V.
5.1
Human Body Model (HBM) Testing
The Human Body Model (HBM) test method emulates the ESD event delivered to an IC during human handling.
The tester delivers the charge through a 1.5kΩ current limiting resistor, so the test is less severe than the
IEC61000 test, which uses a 330Ω limiting resistor. The HBM method determines an IC’s ability to withstand the
ESD transients typically present during handling and manufacturing. Due to the random nature of these events,
each pin is tested with respect to all other pins. The RS-232 pins on “E” family devices can withstand HBM ESD
events to ±15kV.
5.2
IEC61000-4-2 Testing
The IEC61000 test method applies to finished equipment, rather than to an individual IC. Therefore, the pins most
likely to suffer an ESD event are those that are exposed to the outside world (the RS-232 pins in this case), and
the IC is tested in its typical application configuration (power applied) rather than testing each pin-to-pin
combination. The lower current limiting resistor coupled with the larger charge storage capacitor yields a test that
is much more severe than the HBM test. The extra ESD protection built into this device’s RS-232 pins allows the
design of equipment that meets level 4 criteria without the need for additional board level protection on the
RS-232 port.
5.2.1 Air-Gap Discharge Test Method
For the air-gap discharge test method, a charged probe tip moves toward the IC pin until the voltage arcs to it.
The current waveform delivered to the IC pin depends on factors such as approach speed, humidity, and
temperature, so it is difficult to obtain repeatable results. The “E” device RS-232 pins withstand ±15kV air-gap
discharges.
5.2.2 Contact Discharge Test Method
During the contact discharge test, the probe contacts the tested pin before the probe tip is energized and
eliminates the variables associated with the air-gap discharge. The result is a more repeatable and predictable
test, but equipment limits prevent testing devices at voltages higher than ±8kV. All “E” family devices survive ±8kV
contact discharges on the RS-232 pins.
FN6041 Rev.3.00
Apr 26, 2019
Page 19 of 23
ISL4270E
6.
6. Die Characteristics
Die Characteristics
Substrate and QFN Thermal Pad Potential (Powered Up)
GND
Transistor Count
1063
Process
Si Gate CMOS
FN6041 Rev.3.00
Apr 26, 2019
Page 20 of 23
ISL4270E
7.
7. Revision History
Revision History
Rev.
Date
3.00
Apr.26.19
FN6041 Rev.3.00
Apr 26, 2019
Description
Added Related Literature section.
Updated the ordering information table on page 3:
Added ISL4270EIRZ-T
Added tape and reel information and notes 1, 2, and 3.
Added Charge-Pump Abs Max Ratings section starting on page 10.
Applied new template.
Updated disclaimer.
Page 21 of 23
ISL4270E
8.
8. Package Outline Drawing
Package Outline Drawing
For the most recent package outline drawing, see L32.5x5B.
L32.5x5B
32 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
Rev 3, 5/10
4X 3.5
5.00
28X 0.50
A
B
6
PIN 1
INDEX AREA
6
PIN #1 INDEX AREA
32
25
1
5.00
24
3 .30 ± 0 . 15
17
(4X)
8
0.15
9
16
+ 0.07
32X 0.40 ± 0.10
TOP VIEW
0.10 M C A B
4 32X 0.23 - 0.05
BOTTOM VIEW
SEE DETAIL "X"
0.10 C
0 . 90 ± 0.1
C
BASE PLANE
SEATING PLANE
0.08 C
( 4. 80 TYP )
(
( 28X 0 . 5 )
SIDE VIEW
3. 30 )
(32X 0 . 23 )
C
0 . 2 REF
5
( 32X 0 . 60)
0 . 00 MIN.
0 . 05 MAX.
DETAIL "X"
TYPICAL RECOMMENDED LAND PATTERN
NOTES:
1. Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
3. Unless otherwise specified, tolerance : Decimal ± 0.05
4. Dimension applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
5. Tiebar shown (if present) is a non-functional feature.
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
FN6041 Rev.3.00
Apr 26, 2019
Page 22 of 23
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