MAX14912 Datasheet, PDF (17/30 Pages) Maxim Integrated Products – Low Power and Heat Dissipation

MAX14912/MAX14913
Octal High-Speed, High-Side
Switch/Push-Pull Driver
Detailed Description
High-Side Mode
The high-side drivers (HS) have 230mΩ (max) on-resistance
when sourcing 500mA at T_A = +125°C. The OUT_ output
voltage can go below ground, as can occur during
inductive load turn-off/demagnetization. Internal clamping
diodes limit the negative excursion to (V_DD - V_CL) and
allow free-wheeling currents to demagnetize the inductive
loads quickly.
Low-side transistors (LS) can be switched in to provide
push-pull operation. Fast discharge of ground-connected
RC loads is achieved by push-pull drive. In push-pull
mode, the OUT_ outputs are clamped to GND.
Output Parallelization
The devices support paralleling of channels in high-side
mode to provide higher current. The channels can be
paired (1-2, 3-4, 5-6, and 7-8) by setting two bits of the
SPI register 3: joinUP and joinDW (see Table 6).
When joinDW = 1, OUT1 and OUT2 are connected
together, and OUT3 and OUT4 are connected together,
and:
●● Input signals related to channels 2 and 4 are
neglected;
●● Output status is determined by inputs 1 and 3;
●● Push-pull mode is disabled.
When joinUP = 1, OUT5 and OUT6 are connected together,
and OUT7 and OUT8 are connected together, and:
●● Input signals related to channels 6 and 8 are
neglected;
●● Output status is determined by inputs 5 and 7;
●● Push-pull mode is disabled.
The above configuration can be used without any additional
external zener clamping.
Besides pairing of drivers through internal configuration,
multiple OUTs can be operated in parallel by tying the
OUT_ together and driving the inputs simultaneously. In
this case, an external zener clamp is required per output
set for quenching the energy during inductive load turn-
off. The external clamp voltage of this zener diode must
be lower than the minimum internal clamp voltage (V_CL
(min)). The reason is that there is channel-to-channel
variation between the internal clamp voltages. Without an
external zener diode, during turn-off of channels connected
in parallel, the internal clamp with the lowest clamp voltage
turns on and dissipates all the energy.
Channel diagnostics for fault detection remains independent
in case of paralleling the outputs.
Open-Load/Wire Detection
Detection of an open-load condition can be enabled on
a per-channel basis through serial configuration, or glob-
ally in serial mode through the OL/IN1 input. Open-load
detection works in high-side mode only. It operates with
the HS driver either on or off.
When the HS switch is off, a current source is enabled,
which pulls OUT_ to V_DD when the wire is open. If the
OUT_ voltage is above V_{OL_T}, an open load is signaled.
When the HS switch is on, the voltage across the HS
switch is monitored. If this drop is below a load current of
I_{OL_HSON}, an open-load fault is reported.
The switch input state and the load condition must both be
stable for at least t_{DEB_OL} to get a reliable reading.
When an open-load condition is detected on an output:
1) The F_ bit is set for that output in the serial diagnostic
data.
2) The fault LED is turned on for at least 200ms for that
channel.
3) The open-drain global FAULT transistor is turned on
for at least 200ms.
VDD
OPEN
HS
VOL_T
LS
IOL_HSOFF
OPEN
WIRE
OUT_
RL
GND
Figure 4. Open-Wire Load Detection
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