AAT2138 Datasheet, PDF (2/18 Pages) Skyworks Solutions Inc. – High Current Step-Down Converter with High-Precision Programmable Current Limited Load Switch

Pin Descriptions
Pin #
1, 2
Symbol
PGND
3, 4
REGIN
5
ENREG
6
RSET
7
AGND
8
ENSYS
9
FB
10
MODE
11, 12
13, 14
EP
SYSIN
SW
GND (EP)
DATA SHEET
AAT2138
High Current Step-Down Converter
with High-Precision Programmable Current Limited Load Switch
Function
Power Ground. PGND is internally connected to the source of the low-side N-channel MOSFET.
Input Power Supply for the Step-Down Regulator. Connect REGIN to the input power source.
Bypass REGIN to PGND with a 4.7μF or greater ceramic capacitor. REGIN internally connects to
the source of the load switch output and the step-down regulator’s high-side P-channel MOSFET
(see the Functional Block Diagram).
Step-Down Regulator Enable Input. A logic high enables the AAT2138 switching regulator. A
logic low forces the AAT2138 into shutdown mode, placing the output into a high-impedance
state and reducing the quiescent current to less than 1μA. Do NOT leave ENREG floating.
Load Switch Current-Limit Adjustment. Connect a resistor between RSET and ground to set the
input current limit threshold.
Analog Ground. AGND is internally connected to the analog ground of the control circuitry.
Load Switch Enable. Active Low Input. A logic low enables the AAT2138 load switch. A logic high
disables the AAT2138 load switch. Do NOT leave ENSYS floating.
Feedback Input / Output Voltage Sense. FB senses the output voltage for regulation control. For
adjustable output versions, connect a resistive divider network from the output to FB to GND to
set the output voltage accordingly. The FB regulation threshold is 0.6V.
Regulator Operating Mode. Pull MODE high to force the regulator into forced PWM operation.
Pull MODE low to allow automatic pulse-skipping under light-load operation. An external clock in
the range of 1MHz to 3MHz can be connected into MODE as a synchronous clock signal for the
step-down converter to bypass the internal oscillator.
System Load Switch Input. SYSIN connects to the source of the P-channel load switch that lim-
its the system input supply current.
Bias Input Supply for the System and Step-Down Regulator. SYSIN supplies power to the ana-
log and logic control circuitry of the AAT2138.
Inductor Switching Node. SW is internally connected to the source of the high-side P-Channel
MOSFET and the drain of the low-side N-channel MOSFET. Externally connected to the power
inductor as shown in the Typical Application Circuit.
Exposed Pad. Connect directly to the ground plane to reduce the thermal impedance.
Pin Configuration
TDFN33-14
(Top View)
PGND 1
PGND 2
REGIN 3
REGIN 4
ENREG 5
RSET 6
AGND 7
14 SW
13 SW
12 SYSIN
11 SYSIN
10 MODE
9 FB
8 _ENSYS
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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202006C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013