MAX1644EAE-T Datasheet, PDF (5/11 Pages) Maxim Integrated Products – 2A, Low-Voltage, Step-Down Regulator with Synchronous Rectification and Internal Switches

2A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
Typical Operating Characteristics (continued)
(Circuit of Figure 1, T_A = +25°C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
(FBSEL = REF)
4V
V_IN
3V
V_OUT = 1.5V, I_OUT = 2A
V_OUT
20mV/div
2A
I_L
0
V_OUT
50mV/div
V_IN = 3.3V, V_OUT = 1.5V
20μs/div
20μs/div
Pin Description
PIN
1
2, 4
3, 14, 16
5
6
7
8
9
10
11
12
13, 15
NAME
SHDN
IN
LX
SS
COMP
TOFF
FB
GND
REF
FBSEL
V_CC
PGND
FUNCTION
Shutdown Control Input. Drive SHDN low to disable the reference, control circuitry, and internal
MOSFETs. Drive high or connect to V_CC for normal operation.
Supply Voltage Input for the internal PMOS power switch
Connection for the drains of the PMOS power switch and NMOS synchronous-rectifier switch. Connect
the inductor from this node to output filter capacitor and load.
Soft-Start. Connect a capacitor from SS to GND to limit inrush current during start-up.
Integrator Compensation. Connect a capacitor from COMP to V_CC for integrator compensation. See the
Integrator Amplifier section.
Off-Time Select Input. Sets the PMOS power switch off-time during constant-off-time operation. Connect a
resistor from TOFF to GND to adjust the PMOS switch off-time.
Feedback Input for both preset-output and adjustable-output operating modes. Connect directly to
output for fixed-voltage operation or to a resistor-divider for adjustable operating modes.
Analog Ground
Reference Output. Bypass REF to GND with a 1µF capacitor.
Feedback Select Input. Selects AC load-regulation error and output voltage. See Table 2 for program-
ming instructions.
Analog Supply Voltage Input. Supplies internal analog circuitry. Bypass V_CC with a 10Ω and 2.2µF low-
pass filter. See Figure 1.
Power Ground. Internally connected to the internal NMOS synchronous-rectifier switch.
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