SGS Thomson Microelectronics VN771P Datasheet
VN771P
QUAD SMART POWER SOLID STATE RELAY
FOR COMPLETE H BRIDGE CONFIGURATIONS
September 1998
SO-28
TYPE R
DS(on)
*I
OUT
V
CC
VN77 1P 0.135 Ω 14 A 26 V
* Total resistanceof one side in bridge configuration
■ SUITED ASLOWVOLTAGEBRIDGE
■ LINEARCURRENT LIMITATION
■ VERYLOW STAND-BY POWER
DISSIPATION
■ SHORTCIRCUIT PROTECTED
■ STATUSFLAG DIAGNOSTICS
■ OPENDRAIN DIAGNOSTICSOUTPUT
■ INTEGRATEDCLAMPINGCIRCUITS
■ UNDER-VOLTAGEPROTECTION
■ ESDPROTECTION
DESCRIPTION
The VN771P is a device formed by three
monolithic chips housed in a standard SO28
package: a double high side and two low side
switches. Both the double high side and low side
switches are made using STMicroelectronics
VIPower technology. This device is suitable to
drive a DC motor in a bridge configurationas well
as to be used as a quad switch for any low
voltage application. The dual high side switches
have built-in thermal shut-down to protect the
chip from over temperature and short circuit,
status output to provide indication for open load
in off and on state, overtemperature conditions
and stuck-on to V
CC
. The low side switches are
two OMNIFET types (fully autoprotected Power
MOSFET in VIPower technology). They have
built-in thermalshut-down, linear current limitation
and overvoltage clamping. Fault feedback for
thermal intervention can be detected by
monitoringthe voltage at the input pin.
DUALHIGH-SIDE SWITCH
From the falling edge of the input signal, the
status output, initially low to signal a fault
condition (overtemperature or open load
on-state), will go back to a high state with a
different delay in case of overtemperature(tpovl)
and in case of open open load (
tpol
) respectively.
This feature allows to discriminate the nature of
the detected fault. To protect the device against
short circuit and over current condition, the
thermal protection turns the integrated Power
MOS off at a minimum junction temperature of
140
o
C. When this temperature returns to 125oC
the switch is automatically turned on again. In
short circuit the protectionreacts with virtually no
delay, the sensor (one for each channel) being
locatedinside each of the two Power MOS areas.
This positioning allows the device to operate with
one channelin automaticthermal cycling and the
other one on a normal load. An internal function
of the devices ensures the fast demagnetization
of inductive loads with a typical voltage (V
demag
)
of -18V. This function allows to greatly reduces
the power dissipationaccording to the formula:
P
dem
=0.5• L
load
• (I
load
)2• [(VCC+V
demag
)/V
demag
] • f
wheref = switching frequencyand
V
demag
= demagnetizationvoltage.
In this device if the GND pin is disconnected,with
V
CC
not exceeding 16V, both channel will switch
off.
LOW-SIDESWITCHES
During normal operation, the Input pin is
electrically connected to the gate of the internal
power MOSFET. The device then behaves like a
standard power MOSFET and can be used as a
switch from DC to 50 KHz. The only difference
from the user’s standpoint is that a small DC
current (I
iss
) flows into the Input pin in order to
supplythe internalcircuitry.
1/11
BLOCK DIAGRAM
VN771P
2/11
CONNECTION DIAGRAM
PIN FUNCTION
No NAME FUNCTI O N
1, 3, 25, 28 DRAI N 3 Drain of S wit c h 3 (low -s ide switch)
2 INP UT 3 I nput of Switch 3 (low-side switch)
4, 11 N.C. Not Connected
5, 10, 19, 2 4 V
CC
Drain of S wit c h es 1and 2 (high- side s wit ches) and Power S upply Volt age
6 GND Grou nd of Switches 1 and 2 (high -s ide switches)
7 INP UT 1 I nput of Switch 1 (high-side s wit c h )
8 DIAGNO S T IC Diagn os tic of Switc hes 1 and 2 (h igh-side switches )
9 INP UT 2 I nput of Switch 2 (high-side s wit c h )
12, 14, 15, 1 8 DRAIN 4 Drain of S witc h 4 (low-side switch)
13 INP UT 4 I nput of Switch 4 (low-side switch)
16, 17 SO URC E 4 Source of S w it ch 4 (low-side switch)
20, 21 SO URC E 2 Source of S w it ch 2 (high- s ide s wit ch)
22, 23 SO URC E 1 Source of S w it ch 1 (high- s ide s wit ch)
26, 27 SO URC E 3 Source of S w it ch 3 (low-side switch)
VN771P
3/11
PROTECTION CIRCUITS
DUALHIGH SIDESWITCH
The simplest way to protect the device against a
continuous reverse battery voltage (-26V) is to
insert a a small resistor betweenpin 2 (GND) and
ground. The suggested resistance value is about
150Ω. In any case the maximum voltage drop on
this resistorshould not overcome0.5V.
If there is no need for the control unit to handle
external analog signals referred to the power
GND, the best approach is to connect the
reference potential of the control unit to the
device ground (see application circuit in fig. 3),
which becomes the common signal GND for the
whole control board avoiding shift of V
ih,Vil
and
V
stat
.
LOW SIDESWITCHES
The devices integrate:
- OVERVOLTAGE CLAMP PROTECTION:
internally set at 42V, along with the rugged
avalanche characteristics of the Power
MOSFET stage give this device unrivalled
ruggedness and energy handling capability.
This feature is mainly important when driving
inductive loads.
- OVERTEMPERATUREAND SHORT CIRCUIT
PROTECTION: these are based on sensing
the chiptemperature and are notdependent on
the input voltage. The location of the sensing
element on the chip in the power stage area
ensures fast, accurate detection of the junction
temperature. Overtemperaturecutout occurs at
minimum 150
o
C. The device is automatically
restarted when the chip temperature falls
below 135
o
C.
- STATUS FEEDBACK: In the case of an
overtemperature fault condition, a Status
Feedback is provided through the Input pin.
The internal protection circuit disconnects the
input from the gate and connects it instead to
ground via an equivalent resistance of 100 Ω.
The failure can be detected by monitoring the
voltage at the Input pin, which will be close to
ground potential.
Additional features of these devices are ESD
protection according to the Human Body model
and the ability to be driven from a TTL Logic
circuit (with a smallincrease in R
DS(on)
).
TRUTH TABLE (forDual high-sideswitch only)
INP U T 1 INP UT 2 SO URC E 1 SOUR CE 2 DIAGNOSTIC
Normal Operation L
H
L
H
L
H
H
L
L
H
L
H
L
H
H
L
H
H
H
H
Under-voltage X X L L H
Ther mal Shut dow n
Channel 1
HXLX L
Channel 2
XHXL L
Open Load
Channel 1
H
L
X
L
H
L
X
L
L
L
Channel 2
X
L
H
L
X
L
H
L
L
L
Out put Short ed t o V
CC
Channel 1
H
L
X
L
H
H
X
L
L
L
Channel 2
X
L
H
L
X
L
H
H
L
L
NOTE: The low-side switches have the fault feedback which can be detected by monitoringthe voltage at the input pins.
L = Logic LOW, H = Logic HIGH, X = Don’t care
VN771P
4/11
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