ZLDO1117G12TA Diodes Zetex, ZLDO1117G12TA Datasheet - Page 6

• Manufacturer Part Number: ZLDO1117G12TA
• Description: IC REG LDO 1A 1.2V SOT223-3
• Manufacturer: Diodes Zetex

Specifications of ZLDO1117G12TA

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.2V
• Voltage - Input: 2.7 ~ 18 V
• Voltage - Dropout (typical): 1.11V @ 1A
• Number Of Regulators: 1
• Current - Output: 1A (Max)
• Current - Limit (min): 1.1A
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-223 (3 leads + Tab), SC-73, TO-261
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ZLDO1117G12DITR

Pin Descriptions
Applications information
The ZLDO1117 family of quasi-LDO regulators is easy to use. They are protected against short circuit and thermal overloads.
(see block diagram).
Thermal protection circuitry will shut down the regulator should the junction temperature exceed 150°C at the sense point.
The ZLDO1117 is pin compatible with similar ‘1117 regulators and offers extended temperature range and improved
regulation specifications.
Operation
The ZLDO1117 develops a 1.25V reference voltage between the output and the adjust terminal (see block diagram). By
placing a resistor between these two terminals, a constant current is caused to flow through R1 and down through R2. For
fixed output variants Resistors R1 and R2 are internal.
Stability
The ZLDO1117 requires an output capacitor as part of the device frequency compensation. As part of its improved
performance over industry standard 1117 the ZLDO1117 is suitable for use with MLCC (Multi Layer Ceramic Chip) capacitors.
A minimum of 4.7µF ceramic X7R, 4.7µF tantalum, or 47 µF of aluminum electrolytic is required. The ESR of the output
capacitor should be less than 0.5Ω. Surface mount tantalum capacitors, which have very low ESR, are available from several
manufacturers. When using MLCC capacitors avoid the use of Y5V dielectrics.
Load Regulation
For improved load regulation the ZLDO1117-ADJ should have the upper feedback resistor, R
possible to V
parasitic resistance in series with the load.
Thermal Considerations
ZLDO1117 series regulators have internal thermal limiting circuitry designed to protect the device during overload conditions.
For continuous normal load conditions however, the maximum junction temperature rating of 125°C must not be exceeded.
It is important to give careful consideration to all sources of thermal resistance from junction to ambient. For the SOT223-3L
and TO252-3L packages, which are designed to be surface mounted, additional heat sources mounted near the device must
also be considered. Heat sinking is accomplished using the heat spreading capability of the PCB and its copper traces. The
θ
Thermal resistances from tab to ambient can be as low as 30°C/W. The total thermal resistance from junction to ambient can
be as low as 42~46°C/W. This requires a reasonable sized PCB with at least one layer of copper to spread the heat across
the board and couple it into the surrounding air. Datasheet specifications using 2 oz copper and a 5mmx5mm pad with
T
The thermal resistance for each application will be affected by thermal interactions with other components on the board.
Some experimentation will be necessary to determine the actual value.
Ripple Rejection
When using the ZLDO1117 adjustable device the adjust terminal can be bypassed to improve ripple rejection. When the
adjust terminal is bypassed the required value of the output capacitor increases.
ZLDO1117
Document number: Ds32018 Rev. 4 - 2
JC
A
=27°C, no air flow yielded θ
Adj (GND)
(junction to tab) of the TO252-3L and SOT223-3L are 12°C/W and 16°C/W respectively.
NAME
V
V
OUT
IN
OUT
I/O
and the lower resistor, R2, connected as close as possible to the load GND return. This helps reduce any
O
I
I
Pin #
1
2
3
JA
(junction to tab) of 73°C/W and 107°C/W for TO252-3L and SOT223-3L respectively.
The input pin of regulator. Typically a large storage capacitor (0.05Ω ≤ ESR ≤ 0.5Ω) is
connected from this pin to ground to ensure that the input voltage does not sag below
the minimum dropout voltage during the load transient response. This pin must always
be 1.3V higher than V
A resistor divider from this pin to the V
The output of the regulator. A minimum of 4.7µF capacitor (0.05Ω ≤ ESR ≤ 0.5Ω)
(Ground only for Fixed-Mode).
must be connected from this pin to ground to insure stability. For improved ac load
response a larger output capacitor is recommended.
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OUT
6 of 12
in order for the device to regulate properly.
FUNCTION
OUT
pin and ground sets the output voltage
Diodes Incorporated
A Product Line of
1
, connected as close as
ZLDO1117
© Diodes Incorporated
July 2010