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TDE1897CDP Schematic ( PDF Datasheet ) - ST Microelectronics

Teilenummer TDE1897CDP
Beschreibung 0.5A HIGH-SIDE DRIVER INDUSTRIAL INTELLIGENT POWER SWITCH
Hersteller ST Microelectronics
Logo ST Microelectronics Logo 




Gesamt 12 Seiten
TDE1897CDP Datasheet, Funktion
TDE1897C
TDE1898C
0.5A HIGH-SIDE DRIVER
INDUSTRIAL INTELLIGENT POWER SWITCH
0.5A OUTPUT CURRENT
18V TO 35V SUPPLY VOLTAGE RANGE
INTERNAL CURRENT LIMITING
THERMAL SHUTDOWN
OPEN GROUND PROTECTION
INTERNAL NEGATIVE VOLTAGE CLAMPING
TO VS - 45V FOR FAST DEMAGNETIZATION
DIFFERENTIAL INPUTS WITH LARGE COM-
MON MODE RANGE AND THRESHOLD
HYSTERESIS
UNDERVOLTAGE LOCKOUT WITH HYSTERESIS
OPEN LOAD DETECTION
TWO DIAGNOSTIC OUTPUTS
OUTPUT STATUS LED DRIVER
DESCRIPTION
The TDE1897C/TDE1898C is a monolithic Intelli-
gent Power Switch in Multipower BCD Technol-
BLOCK DIAGRAM
PRELIMINARY DATA
MULTIPOWER BCD TECHNOLOGY
Minidip
SIP9
SO20
ORDERING NUMBERS:
TDE1897CDP
TDE1898CDP
TDE1898CSP
TDE1897CFP
TDE1898CFP
ogy, for driving inductive or resistive loads. An in-
ternal Clamping Diode enables the fast demag-
netization of inductive loads.
Diagnostic for CPU feedback and extensive use
of electrical protections make this device inher-
ently indistructible and suitable for general pur-
pose industrial applications.
October 1995
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TDE1897CDP Datasheet, Funktion
TDE1897C - TDE1898C
WORST CONDITION POWER DISSIPATION IN
THE ON-STATE
In IPS applications the maximum average power
dissipation occurs when the device stays for a
long time in the ON state. In such a situation the
internal temperature depends on delivered cur-
rent (and related power), thermal characteristics
of the package and ambient temperature.
At ambient temperature close to upper limit
(+85°C) and in the worst operating conditions, it is
possible that the chip temperature could increase
so much to make the thermal shutdown proce-
dure untimely intervene.
Our aim is to find the maximum current the IPS
can withstand in the ON state without thermal
shutdown intervention, related to ambient tem-
perature. To this end, we should consider the fol-
lowing points:
1) The ON resistance RDSON of the output
NDMOS (the real switch) of the device in-
creases with its temperature.
Experimental results show that silicon resistiv-
ity increases with temperature at a constant
rate, rising of 60% from 25°C to 125°C.
The relationship between RDSON and tem-
perature is therefore:
R DSON = R DSON0 ( 1 + k ) ( T j ± 25 )
where:
Tj is the silicon temperature in °C
RDSON0
k is the
is RDSON
constant
at Tj=25°C
rate (k = 4.711
10
±3)
(see fig. 4).
2) In the ON state the power dissipated in the
device is due to three contributes:
a) power lost in the switch:
P out = I out 2 R DSON (Iout is the output cur-
rent);
b) power due to quiescent current in the ON
state Iq, sunk by the device in addition to
Iout: P q = I q V s (Vs is the supply voltage);
c) an external LED could be used to visualize
the switch state (OUTPUT STATUS pin).
Such a LED is driven by an internal current
source (delivering Ios) and therefore, if Vos is
the voltage drop across the LED, the dissi-
pated power is: P os = I os ( V s ± V os ).
Thus the total ON state power consumption is
given by:
P on = P out + P q + P os
(1)
In the right side of equation 1, the second and
6/12
the third element are constant, while the first
one increases with temperature because
RDSON increases as well.
3) The chip temperature must not exceed ΘLim
in order do not lose the control of the device.
The heat dissipation path is represented by
the thermal resistance of the system device-
board-ambient (Rth). In steady state condi-
tions, this parameter relates the power dissi-
pated Pon to the silicon temperature Tj and
the ambient temperature Tamb:
T j ± T amb = P on R th
(2)
From this relationship, the maximum power
Pon which can be dissipated without exceed-
ing ΘLim at a given ambient temperature
Tamb is:
P
on
=
ΘLim ± T
R th
amb
Replacing the expression (1) in this equation
and solving for Iout, we can find the maximum
current versus ambient temperature relation-
ship:
I outx =
ΘLim ± T
R th
amb
±
P
q
±
P
os
R DSONx
where RDSONx is RDSON at Tj=ΘLim. Of
course, Ioutx values are top limited by the
maximum operative current Ioutx (500mA
nominal).
From the expression (2) we can also find the
maximum ambient temperature Tamb at which
a given power Pon can be dissipated:
T amb = ΘLim ± P on R th =
= ΘLim ± ( I out 2 R DSONx + P q + P os ) R th
In particular, this relation is useful to find the
maximum ambient temperature Tambx at
which Ioutx can be delivered:
T ambx = ΘLim ± ( I outx 2 R DSONx +
+ P q + P os ) R th
(4)
Referring to application circuit in fig. 5, let us con-
sider the worst case:
- The supply voltage is at maximum value of in-
dustrial bus (30V instead of the 24V nominal
value). This means also that Ioutx rises of 25%

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TDE1897CDP pdf, datenblatt
TDE1897C - TDE1898C
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the
consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No
license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specification mentioned
in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-
THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express
written approval of SGS-THOMSON Microelectronics.
© 1995 SGS-THOMSON Microelectronics – Printed in Italy – All Rights Reserved
SGS-THOMSON Microelectronics GROUP OF COMPANIES
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