The L7900AC series of three-terminal negative
regulators is available in TO-220 and D
packages and several fixed output voltages.
These regulators can provide local on-card
regulation, eliminating the distribution problems
associatedwithsinglepointregulation;
furthermore, having the same voltage option as
the L7800A positive standard series, they are
particularly suited for split power supplies. In
addition, the -5.2V is also available for ECL
system.If adequate heat sinking is provided,
they can deliver over 1.5A output current.
Although designed primarily as fixed voltage
regulators, these devices can be used with
externalcomponentstoobtainadjustable
voltagesand currents.
* Load and line regulation are specified at constant junction temperature. Changes in Vodue to heating effects must be taken into account
separately. Pulce testing with low duty cycle is used.
* Load and line regulation are specified at constant junction temperature. Changes in Vodue to heating effects must be taken into account
separately. Pulce testing with low duty cycle is used.
* Load and line regulation are specified at constant junction temperature. Changes in Vodue to heating effects must be taken into account
separately. Pulce testing with low duty cycle is used.
* Load and line regulation are specified at constant junction temperature. Changes in Vodue to heating effects must be taken into account
separately. Pulce testing with low duty cycle is used.
* Load and line regulation are specified at constant junction temperature. Changes in Vodue to heating effects must be taken into account
separately. Pulce testing with low duty cycle is used.
= -27to-38 V
V
i
= -30to-36 V Tj=25oC
V
i
=250to750mA Tj=25oC
I
o
=10 Vf = 120Hz5460dB
i
V
=100mV
∆
O
15 W
≤
o
-23-24-25V
480
240
480
240
mV
mV
mV
mV
1.1V
7/11
L7900AC
APPLICATION INFORMATION
Figure1 : Fixed OutputRegulator.Figure2 : SplitPowerSupply (± 15V/1A).
Notes :
1. To specify an output voltage, substitute voltagevaluefor ”XX”.
2. Required for stability. For value given, capacitor must be solid
tantalum. If aluminium electrolitics are used, at least ten times
value should be selected. C
appreciable distance from power supply filter.
3. To improve transient response. If large capacitors are used, a
high current diode from input to output (1N4001 or similar) should
be introduced to protect the device from momentary input short
circuit.
is required if regulator is located an
1
Against potentiallatch-up problems.
Figure 3 : Circuitfor IncreasingOutputVoltage.Figure 4 : High Current Negative Regulator
(– 5V/4A with 5A current limiting).
R
+
R
1
=
V
V
O
XX
2
R
2
V
XX
> 3
I
d
R
2
C3 Optional forimprovedtransient response and ripple rejection.
Figure5 : Typical ECL System Power Supply
(– 5.2V/4A).
Optional dropping resistor to reduce the power dissipated in the
boost transistor.
Information furnished isbelieved tobe accurate andreliable. However, STMicroelectronics assumes no responsibility fortheconsequences
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 STMicroelectronics. Specification mentioned in this publication are
subject to change without notice. Thispublication supersedes andreplaces all information previously supplied. STMicroelectronics products
are not authorized for use as critical components in life support devices or systems withoutexpress written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics
1999 STMicroelectronics – Printed in Italy – All Rights Reserved
STMicroelectronics GROUP OF COMPANIES
Australia - Brazil - China - Finland - France - Germany - Hong Kong - India- Italy - Japan- Malaysia - Malta - Morocco
Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A.
http://www.st.com
.
11/11
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