HIP9022AM Intersil Corporation, HIP9022AM Datasheet - Page 9

• Manufacturer Part Number: HIP9022AM
• Description: Dual High Speed Laser Driver
• Manufacturer: Intersil Corporation

Both analog and digital data is input to control the action of
the dual laser driver. Address codes and input data are
described in the Table 1 Address Map. Digital data is
normally entered first, followed by the analog data via the
multiplexed analog bus which updates the S/H stored
voltage levels. Four bit digital addresses to pins A3, A2, A1
and A0 are decoded to define the programming functions
for data input. It is important to note that Address 15 is a
reset for Addresses 9 - 14 and should be performed as the
first step in programming because there is no power-on-
reset on-chip.
Diagnostic Output Data
For the purpose of monitoring on-chip signals, the
multiplexed bus can be used to output signals (at the DIAG
pin) via an analog diagnostic amplifier. This mode has the
capability to monitor the multiplexed output of four (0-5V)
analog signals for each laser channel. Note that the
diagnostic information at the VLOW (Amplifier A3) output is
2:1 resistor divided to +5V (V
to 5V range. To minimize noise problems the monitoring
function is normally performed during the laser scan for only
one signal per scan. In addition, there are 3 test modes
which allows the bus to present analog signals for testing the
performance of the eight S/H circuits.
Thermo-Electric-Cooler (TEC) Circuitry
Figure 4 shows the Thermal Electric Cooler (TEC) drive
circuit with an external reference resistance, a thermo-
resistor to sense temperature plus feedback components for
stable drive. There is a thermo-resistor reference input on
the chip for monitoring the laser's temperature via a 5-10k
thermo-resistor which must be mounted near the laser. A
reference voltage on the external reference resistor is
established by a current from a stable bias source. This
current is mirrored to the thermo-resistor (one for each laser
driver system). A comparator senses the voltage across the
reference resistor versus the voltage across the thermo-
FIGURE 4. TEC (THERMAL ELECTRIC COOLER) CIRCUIT WITH REFERENCE RESISTOR AND THERMAL RESISTOR SENSOR OF
1.9V
LASER TEMPERATURE
+
-
4-9
CURRENT
CC
MIRROR
) to return this signal to a 0
O.T.
U.T.
+
1
2
+
-
TEMP.
COMP.
-
+
48
47
46
45
44
43
TECFB2
HIP9022
TECREF2
TRES2
TECREFR
TECGDR2
OT2
REFERENCE
RESISTOR
resistor and drives the gate of the TEC FET driver. As such,
the TEC circuit senses the thermo-resistor input as a
measure of the laser temperature and the TEC drive is
adjusted to maintain a stable Laser temperature slightly
below the ambient temperature. An external Power FET is
needed to provide the high TEC driver currents. An out of
range temperature output for each laser is also provided.
Laser Protection Diodes
Another feature included on the chip is two high current ESD
diodes which, in the printer system, are used to protect the
Laser Diodes from ESD damage. Another component of Laser
protection in printer systems are relays to disconnect the
Lasers when in a non-operating mode. For this purpose, a
single relay driver is included.
Over Current Flag Output (OC1, OC2)
Over-current detection is also included on-chip. The circuit of
Figure 3 shows the over current detection circuit. For each
laser source current driver, the over current monitor compares
the S/H input of amplifier A2 to the output of amplifier A1. If
the output voltage of A1 exceeds the input of A2 by 40%, then
an over current state exists and the OC output will go high.
Invert Option
An INVERT input reconfigures the device such that the
constant current source can be high side instead of the
normal low side. This provides functionality for driving laser
diodes in a common cathode configuration as opposed to
the normal common anode configuration. The INVERT must
be low (or open with the internal pull down) for the Figure 1
circuit.
Reset Action
The RESETB (active low) controls three things:
(1) The TEC driver is turned off.
(2) The Shunt driver is turned on to turn off the laser.
(3) The Constant current driver is turned off.
Q2
TEC
+
LASER2
THERMALLY
COUPLED
COMPONENTS
THERMO-
RESISTOR
(TEMPERATURE SENSOR)