LT3582EUD-12#TRPBF Linear Technology, LT3582EUD-12#TRPBF Datasheet - Page 14

• Manufacturer Part Number: LT3582EUD-12#TRPBF
• Description: IC DC/DC CONV +/-12V 16-QFN
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Invertingr

Specifications of LT3582EUD-12#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: ±12V
• Current - Output: 350mA, 600mA
• Voltage - Input: 2.55 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-WQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -

LT3582/LT3582-5/LT3582-12
APPLICATIONS INFORMATION
OTP2/REG2: Data in address 02h confi gures the output
voltage sequencing, sets a fi ne voltage adjust for V
and determines if further OTP programming is permitted or
not. Proper uses of the bits in address 02h are discussed
in the following sections.
Setting the Output Voltages (V
The LT3582 series contains two resistor dividers which are
programmable in the LT3582, to set the output voltages.
The positive output voltage V
steps by setting the V
the V
where:
The V
the V
where:
Dynamically Changing the Output Voltage (LT3582 Only):
After output regulation has been reached, it’s possible to
change the output voltages by writing new values to the
V
put voltage, it will decay at a rate dependent on the load
current and capacitance. Confi guring a large increase in
magnitude of an output voltage can cause a large increase
in switch current to charge the output capacitor. Before
reconfi guring the outputs, consider forcing a soft-start
by asserting the SWOFF bit before writing the new V
V
soft-start sequence.
14
N
N
V
V
V
V
V
codes. Subsequently clearing SWOFF initiates the new
or V
OUTP
P
PLUS
OUTN
N
PLUS
N
OUTN
= an integer value from 0 to 191
= an integer value from 0 to 255
bits in REG1/OTP1.
P
= 0 or 1
= 3.2V + (V
= –1.2V – (V
bits. When reducing the magnitude of an out-
bit in REG2/OTP2.
voltage is adjustable in –50mV steps by setting
P
P
N
• 50mV) + (V
bits in REG0/OTP0 in addition to
• 50mV)
OUTP
P
, V
is adjustable in 25mV
PLUS
PLUS
and V
• 25mV)
N
Bits)
OUTP
P
or
,
Soft-Start/Output Voltage Ramping (IRMP Bits)
The LT3582 series contains soft-start circuitry to control the
output voltage ramp rates, therefore limiting peak switch
currents during start-up. High switch currents are inherent
in switching regulators during start-up since the feedback
loop is saturated due to V
The regulator tries to charge the output capacitor as quickly
as possible which results in large currents.
Capacitors must be connected from RAMPP and RAMPN
to ground for soft-start. During shutdown or when the
SWOFF bit is set, the RAMP capacitors are discharged
to ground. After SHDN rises or SWOFF is cleared, the
capacitors are charged by programmable (LT3582 only)
currents, thus creating linear voltage ramps. The V
voltages ramp in proportion to their respective RAMP
voltages according to:
Proportionality Constant
RAMP pin ramp rate (V/Sec)
where:
For example, selecting I
V
(see Figure 6).
Ramp rates less than 1-10V/ms generally result in good
start-up characteristics. The outputs should linearly follow
the RAMPx voltages with no distortions. Figure 7 shows
an excessive start-up ramp rate of ~120V/ms in which
V
OUTP
OUT
I
C
V
RAMP
RAMP
OUT
_RAMP _RATE =
= 12V results in a power-up ramp rate of 1.5Volt/ms
= RAMP pin charging current set by IRMP
= External RAMP pin capacitor (Farads)
= Output voltage during regulation
bits (1μA, 2μA, 4μA or 8μA for LT3582,
1μA for LT3582-5/LT3582-12)
⎛
⎝ ⎜
RAMP
OUT
V
0.8V
OUT
being far from its fi nal value.
= 1μA, C
⎞
⎠ ⎟
•
⎛
⎝ ⎜
C
I
RAMP
RAMP
RAMP
⎞
⎠ ⎟
= 10nF and
Volts / Sec
3582512fb
OUT