LT1330 Ver la hoja de datos (PDF) - Linear Technology
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LT1330
Linear Technology
LT1330 Datasheet PDF : 8 Pages
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LT1330
PI FU CTIO S
to reduce supply ripple. The ratio of the capacitors on V+
and V – should be greater than 5 to 1.
V–: Negative Supply Output. V – ≈ –(2VCC – 2.5V). This pin
requires an external charge storage capacitor, C ≥ 0.1µF.
See the Applications Information section for guidance in
choosing filter capacitors for V+ and V –.
C1+, C1–, C2+, C2–: Commutating Capacitor Inputs re-
quire two external capacitors, C ≥ 0.2µF: one from C1+ to
C1–, and another from C2+ to C2–. The capacitor’s effec-
tive series resistance should be less than 2Ω. For C ≥ 1µF,
low ESR tantalum capacitors work well, although ceramic
capacitors may be used with a minimal reduction in charge
pump compliance.
DRIVER IN: RS232 Driver Input Pins. These inputs are
TTL/CMOS compatible. Unused inputs should be con-
nected to VCC.
DRIVER OUT: Driver Outputs at RS232 Voltage Levels.
Driver output swing meets RS232 levels for loads up to 3k.
Slew rates are controlled for lightly loaded lines. Output
current capability is sufficient for load conditions up to
2500pF. Outputs are in a high impedance state when in
shutdown mode, VCC = 0V, or when the DRIVER DISABLE
pin is active. Outputs are fully short-circuit protected from
V – + 30V to V+ – 30V. Applying higher voltages will not
damage the device if the overdrive is moderately current
limited. Short circuits on one output can load the power
supply generator and may disrupt the signal levels of the
other outputs. The driver outputs are protected against
ESD to ±10kV for human body model discharges.
RX IN: Receiver Inputs. These pins accept RS232 level
signals (±30V) into a protected 5k terminating resistor.
The receiver inputs are protected against ESD to ±10kV for
human body model discharges. Each receiver provides
0.4V of hysteresis for noise immunity. Open receiver
inputs assume a logic low state.
RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-
els. Outputs are in a high impedance state when in shut-
down mode to allow data line sharing. Outputs, including
LOW-Q RX OUT, are fully short-circuit protected to ground
or VCC with the power on, off, or in shutdown mode.
LOW Q-CURRENT RX IN: Low Power Receiver Input. This
special receiver remains active when the part is in shut-
down mode, consuming typically 60µA. This receiver has
the same 5k input impedance and ±10kV ESD protection
characteristics as the other receivers.
LOW Q-CURRENT RX OUT: Low Power Receiver Output.
This pin produces the same TTL/CMOS output voltage
levels as receivers RX1, RX2, RX3, and RX4 with slightly
decreased speed and short-circuit current. Data rates to
120kbaud are supported by this receiver.
U
ESD PROTECTIO
The RS232 line inputs of the LT1330 have on-chip protec-
tion from ESD transients up to ±10kV. The protection
structures act to divert the static discharge safely to
system ground. In order for the ESD protection to function
effectively, the power supply and ground pins of the
LT1330 must be connected to ground through low imped-
ances. The power supply decoupling capacitors and charge
pump storage capacitors provide this low impedance in
normal application of the circuit. The only constraint is that
low ESR capacitors must be used for bypassing and
charge storage. ESD testing must be done with pins VCC,
VL, V+, V –, and GND shorted to ground or connected with
low ESR capacitors.
ESD Test Circuit
1µF
RS232
LINE PINS
PROTECTED
TO ±10kV
V+ 1
5V VCC 2
0.1µF
3
0.2µF
4
5
DRIVER 1 OUT
RX1 IN 6
7
DRIVER 2 OUT
8
RX2 IN
RX3 IN 9
10
RX4 IN
11
DRIVER 3 OUT
12
RX5 IN (LOW-Q)
ON/OFF 13
14
3V VL
0.1µF
LT1330
28 V–
27
0.1µF
26
0.2µF
25
DRIVER 1 IN
24
RX1 OUT
23 DRIVER 2 IN
22
RX2 OUT
21
RX3 OUT
20 RX4 OUT
19
DRIVER 3 IN
18
RX5 OUT (LOW-Q)
17
GND
16
DRIVER DISABLE
15
1330 TC01
6
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