MAX1644 Maxim, MAX1644 Datasheet - Page 5

• Manufacturer Part Number: MAX1644
• Description: Advanced Chemistry-Independent / Level 2 Battery Charger with Input Current Limiting
• Manufacturer: Maxim

(Circuit of Figure 1, T
3, 14, 16
13, 15
PIN
2, 4
10
11
12
1
5
6
7
8
9
Synchronous Rectification and Internal Switches
20mV/div
V
OUT
V
4V
3V
NAME
COMP
FBSEL
SHDN
PGND
IN
TOFF
GND
REF
V
LX
SS
FB
IN
CC
V
OUT
_______________________________________________________________________________________
A
LINE-TRANSIENT RESPONSE
2A, Low-Voltage, Step-Down Regulator with
= +25°C, unless otherwise noted.)
= 1.5V, I
Shutdown Control Input. Drive SHDN low to disable the reference, control circuitry, and internal
MOSFETs. Drive high or connect to V
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
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
pass filter. See Figure 1.
Power Ground. Internally connected to the internal NMOS synchronous-rectifier switch.
OUT
20μs/div
= 2A
Typical Operating Characteristics (continued)
CC
for normal operation.
FUNCTION
50mV/div
V
OUT
2A
I
0
L
V
CC
IN
LOAD-TRANSIENT RESPONSE
= 3.3V, V
for integrator compensation. See the
(FBSEL = REF)
OUT
CC
= 1.5V
20μs/div
with a 10Ω and 2.2µF low-
Pin Description
5