10 FN3138.16
September 26, 2008
Detailed Description
The HIN232 thru HIN241 family of RS-232
transmitters/receivers are powered by a single +5V power
supply (except HIN239), feature low power consumption, and
meet all ElA RS-232C and V.28 specifications. The circuit is
divided into three sections: The charge pump, transmitter , and
receiver.
Charge Pump
An equivalent circuit of the charge pump is illustrated in
Figure 1. The charge pu mp cont ains two sections: the volt age
doubler and the volt age in verter. Each section is driven by a
two-phase, internally genera ted cl ock to generate +10V and
-10V. The nominal clock frequency is 16kHz. During phase
one of the clock, cap acitor C1 is cha rged to VCC. During
phase two, the voltage on C1 is added to VCC, producing a
signal across C3 equal to tw ice VCC. During phase one, C2 is
also charged to 2VCC, and then during phase two, it is
inverted with respect to ground to produce a signal across C4
equal to -2VCC. The charge pump accepts inpu t volta ges up
to 5.5V. The output impedance of the volt age do ubler section
(V+) is approximately 200Ω, and the o utput impedance of the
voltage inverter section (V-) is approximately 450Ω. A typical
application uses 1µF capacitors for C1-C4, however , the value
is not critical. Increasing the values of C1 and C2 will low er the
output impedance of the voltage doub ler and inverter,
increasing the values of the reservoir capa citors, C3 and C4,
lowers the ripple on the V+ and V- supplies.
During shutdown mode (HIN236, HIN240 and HIN241),
SHUTDOWN control line set to logic “1”, the charge pump is
turned off, V+ is pulled down to VCC, V - is pulled up to GND,
and the supply current is reduced to less than 10µA. The
transmitter outputs are disabled and the receiver outputs are
placed in the high impedance state.
TIMING CHARACTERISTICS
Baud Rate (1 Transmitter Switching) RL = 3kΩ120 - - kbps
Output Enable Time, tEN HIN236, HIN239, HIN240, HIN241 - 400 - ns
Output Disable Time, tDIS HIN236, HIN239, HIN240, HIN241 - 250 - ns
Propagation Delay, tPD RS-232 to TTL - 0.5 - µs
Instantaneous Slew Rate SR CL = 10pF, RL = 3kΩ, TA = +25°C (Note 4) - - 30 V/µs
Transition Region Slew Rate, SRTRL = 3kΩ, CL = 2500pF Measured from +3V to -3V
or -3V to +3V, 1 Transmitter Switching -3-V/µs
TRANSMITTER OUTPUTS
Output Voltage Swing, TOUT Transmitter Outputs, 3kΩ to Ground ±5 ±9 ±10 V
Output Resistance, TOUT VCC = V+ = V- = 0V, VOUT = ±2V 300 - - Ω
RS-232 Output Short Circuit Current, ISC TOUT shorted to GND - ±10 - mA
NOTE:
4. Limits established by characterization and are not production tested.
5. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. T emperature limits established by characterization
and are not production tested.
Electrical Specifications Test Conditions: VCC = +5V ±10%, TA = Operating Temperature Range (Continued)
PARAMETER TEST CONDITIONS MIN
(Note 5) TYP MAX
(Note 5) UNITS
+
-C1 +
-C3 +
-C2 +
-C4
S1 S2 S5 S6
S3 S4 S7 S8
VCC GND
RC
OSCILLATOR
VCC
GND
V+ = 2VCC
GND
V- = -(V+)
C1+
C1- C2-
C2+
VOLTAGE INVERTER
VOLTAGE DOUBLER
FIGURE 1. CHARGE PUMP
HIN232, HIN236, HIN237, HIN238, HIN239, HIN240, HIN241