LT3032EDE#TRPBF Linear Technology, LT3032EDE#TRPBF Datasheet - Page 19

• Manufacturer Part Number: LT3032EDE#TRPBF
• Description: IC REG LDO ADJ .15A DUAL 14DFN
• Manufacturer: Linear Technology

Specifications of LT3032EDE#TRPBF

• Regulator Topology: Positive and Negative Adjustable
• Voltage - Output: ±1.22 ~ ±20 V
• Voltage - Input: ±2.3 ~ ±20 V
• Voltage - Dropout (typical): 0.27V @ 150mA, 0.3V @ -150mA
• Number Of Regulators: 2
• Current - Output: 150mA
• Current - Limit (min): 170mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

applicaTions inForMaTion
In situations where the ADJP pin is connected to a resistor
divider that would pull the ADJP pin above its 7V clamp
voltage if the output is pulled high, the ADJP pin input
current must be limited to less than 5mA. For example, a
resistor divider is used to provide a 1.5V output from the
1.22V reference and the output is forced to 20V. The top
resistor of the divider must be chosen to limit the current
into the ADJP pin to less than 5mA when the ADJP pin is
at 7V. The 13V difference between OUTP and ADJP divided
by the 5mA maximum current into the ADJP pin yields a
minimum top resistor value of 2.6k.
In circuits where a backup battery is required on the positive
output, several different input/output conditions can occur.
The output voltage may be held up while the input is either
pulled to ground, pulled to some intermediate voltage or
is left open circuit. Current flow back into OUTP follows
the curve shown in Figure 6.
If the INP pin is forced below the OUTP pin or the OUTP pin
is pulled above the INP pin, input current typically drops to
less than 2µA. This can happen if the device is connected
to a discharged (low voltage) bat-tery and the output is
held up by a backup battery or a second regulator circuit.
The state of the SHDNP pin has no effect on the reverse
output current if OUTP is pulled above INP.
100
90
80
70
60
50
40
30
20
10
0
Figure 6. Reverse Output Current
0
T
CURRENT FLOWS
INTO OUTP PIN
V
J
OUTP
1
= 25°C, V
= V
2
ADJP
OUTP PIN VOLTAGE (V)
3
INP
= 0V
4
5
6
7
8
3032 F06
9
10
Like many IC power regulators, the negative side of the
LT3032 has safe operating area (SOA) protection. The safe
operating area protection activates when the differential
voltage between INN and OUTN is greater than -7V. The
SOA protection decreases current limit as a function of
the voltage differential between INN and OUTN and keeps
the power transistor inside a safe operating region for all
values of forward input-to-output voltage. The protection
is designed to provide some output current at all values
of INN to OUTN differential voltage up to the Absolute
Maximum Rating. A 50µA load is required to maintain
regulation for INN to OUTN differential voltages greater
than –7V.
When power to the negative side is first turned on, as
the input voltage rises, OUTN follows INN, allowing the
regulator to start into very heavy loads. During start-up, as
the INN voltage is rising, the differential voltage between
INN and OUTN is small, allowing the negative side to supply
large output currents. With a high INN voltage, a problem
can occur wherein removal of an output short will not
allow the output voltage to fully recover. Other regulators,
such as the LT1175, LT1964, and LT3080 also exhibit this
phenomenon, so it is not unique to the LT3032.
The problem occurs with a heavy output load when the
INN voltage is high and the OUTN voltage is low. Common
situations are immediately after the removal of a short-
circuit or when the SHDNN pin is pulled high after the INN
pin has already been turned on. The load line for such a
load may intersect the output current curve at two points. If
this happens, there are two stable operating points for the
negative side of the LT3032. With this double intersection,
the INN supply may need to be cycled down to zero and
brought up again to make OUTN recover.
LT3032 Series
19
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