MAX14802/MAX14803/MAX14803A
Low-Charge Injection, 16-Channel,
High-Voltage Analog Switches
10
Maxim Integrated
Detailed Description
The MAX14802/MAX14803/MAX14803A provide high-
voltage switching on 16 channels for ultrasound imag-
ing and printer applications. The devices utilize
HVCMOS process technology to provide 16 high-volt-
age low-charge-injection SPST switches, controlled by
a digital interface. Data is clocked into an internal 16-
bit shift register and retained by a programmable latch
with enable and clear inputs. A power-on-reset function
ensures that all switches are open on power-up.
The MAX14802/MAX14803/MAX14803A operate with a
wide range of high-voltage supplies including: V
PP
/V
NN
= +100V/-100V, +200V/0V, or +40V/-160V. The digital
interface operates from a separate +2.7V to +5.5V V
DD
supply. Digital inputs DIN, CLK, LE, and CLR operate
on the V
DD
supply voltage. The MAX14803/MAX14803A
provide integrated 35kΩ bleed resistors on each switch
terminal to discharge capacitive loads. The MAX14802/
MAX14803/MAX14803A feature clamping diodes (at
the COM_). These clamping diodes provide overvolt-
age protection against positive overshoot.
Analog Switch
The MAX14802/MAX14803/MAX14803A allow a peak-to-
peak analog signal range from V
NN
to the minimum of
either V
NN
+ 200V or (V
PP
- 10V). Analog switch inputs
must be unconnected, or satisfy V
NN
≤ (V
COM_
, V
NO_
) ≤
V
PP
during power-up and power-down.
High-Voltage Supplies
The MAX14802/MAX14803/MAX14803A allow a wide
range of high-voltage supplies. The devices operate
with V
NN
from -160V to 0 and V
PP
from +40V to V
NN
+
250V. When V
NN
is connected to GND (single-supply
applications), the devices operate with V
PP
up to
+200V. The V
PP
and V
NN
high-voltage supplies are not
required to be symmetrical, but the voltage difference
(V
PP
- V
NN
) must not exceed 250V.
Bleed Resistors (MAX14803/MAX14803A)
The MAX14803/MAX14803A feature integrated 35kΩ
bleed resistors to discharge capacitive loads such as
piezoelectric transducers. Each analog switch terminal
is connected to GND with a bleed resistor.
Overvoltage Protection
The MAX14802/MAX14803/MAX14803A feature clamp-
ing diodes (at the COM_). These clamping diodes pro-
vide overvoltage protection against positive overshoot.
Serial Interface
The MAX14802/MAX14803/MAX14803A are controlled
by a serial interface with a 16-bit serial shift register
and transparent latch. Each of the 16 data bits controls
a single analog switch (Table 1). Data on DIN is
clocked with the most significant bit (MSB) first into the
shift register on the rising edge of CLK. Data is clocked
out of the shift register onto DOUT on the rising edge of
CLK. DOUT reflects the status of DIN, delayed by 16
clock cycles (Figures 1 and 2).
Latch Enable (
LE
)
Drive LE logic-low to change the contents of the latch
and update the state of the high-voltage switches
(Figure 2). Drive LE logic-high to freeze the contents of
the latch and prevent changes to the switch states. To
reduce noise due to clock feedthrough, drive LE logic-
high while data is clocked into the shift register. After
the data shift register is loaded with valid data, pulse
LE logic-low to load the contents of the shift register
into the latch.
Latch Clear (CLR)
The MAX14802/MAX14803/MAX14803A feature a latch
clear input. Drive CLR logic-high to reset the contents
of the latch to zero and open all switches. CLR does
not affect the contents of the data shift register. Pulse
LE logic-low to reload the contents of the shift register
into the latch.
Power-On Reset
The MAX14802/MAX14803/MAX14803A feature a
power-on-reset circuit to ensure all switches are open
at power-on. The internal 16-bit serial shift register and
latch are set to zero on power-up.
