MAX1572ETC250 Maxim Integrated Products, MAX1572ETC250 Datasheet - Page 7

• Manufacturer Part Number: MAX1572ETC250
• Description: DC/DC Switching Converters 800mA 2MHz PWM Step-Down w/Reset
• Manufacturer: Maxim Integrated Products

Table 1. Mode Select Truth Table
Figure 1 is the functional diagram.
The MAX1572 uses a 2MHz fixed-frequency, pulse-
width-modulated (PWM), current-mode control scheme.
The heart of the current-mode PWM controller is an
open-loop comparator that compares the error amp
voltage-feedback signal against the sum of the ampli-
fied current-sense signal and the slope compensation
ramp. At each rising edge of the internal clock, the
internal high-side P-channel MOSFET turns on until the
PWM comparator trips. During this on-time, current
ramps up through the inductor, sourcing current to the
A zero represents EN_ being driven low or connected to GND.
A 1 represents EN_ being driven high or connected to BATT.
Shutdown
Pulse group
Pulse skip
Forced PWM
3, 5, 11
PIN
10
12
—
1
2
4
6
7
8
9
MODE
Exposed
ABATT
Paddle
RESET
NAME
PGND
BATT
GND
OUT
EN2
EN1
SS
LX
_______________________________________________________________________________________
Active-Low RESET Output. Open-drain output with internal 14kΩ pullup to OUT. RESET is driven LOW in
shutdown.
Soft-Start Control. Connect a capacitor from SS to GND to set the soft-start time. Use a 1000pF or larger
capacitor to eliminate inrush current during startup. With greater than 10µF total output capacitance, increase
C
Ground. Connect all ground pins to the exposed paddle.
Output Sense Input. Connect to the output of the regulator. In shutdown, OUT is discharged internally with
14kΩ to GND.
Enable/Mode Control Input 2. See Table 1.
Power Ground. Connect to exposed paddle.
Inductor Connection. LX is high impedance in shutdown.
S up p l y V ol tag e Inp ut. C onnect to a 2.6V to 5.5V sour ce. C onnect a 10µF cer am i c cap aci tor fr om BATT to G N D .
Enable/Mode Control Input 1. See Table 1.
Anal og S up p l y Inp ut. C onnect to BATT thr oug h a 10Ω r esi stor . C onnect a 0.1µF cap aci tor fr om ABATT to GN D .
Exposed Paddle. Connect to GND and PGND.
SS
Detailed Description
to C
EN1
0
0
1
1
PWM Control Scheme
OUT
/10,000 for soft-start. In shutdown, SS is discharged internally with 100Ω to GND.
Step-Down Converter with RESET
800mA, 2MHz, PWM DC-to-DC
EN2
0
1
0
1
Figure 1. Functional Diagram
FUNCTION
EN2
EN1
RESET
MAX1572
SHUTDOWN
REFERENCE
CURRENT
THERMAL
SELECT
MODE
SENSE
SLOPE
COMP
RESET
TIMER
170ms
CLOCK
2MHz
EA
CONTROL
PWM
SS
1000pF
Pin Description
ABATT
PGND
BATT
GND
OUT
LX
10Ω
10µF
2.2µH
0.1µF
0.75V TO 2.5V
2.6V TO 5.5V
C
OUT
OUTPUT
800mA
INPUT
7