MAX8500 MAXIM [Maxim Integrated Products], MAX8500 Datasheet - Page 7

• Manufacturer Part Number: MAX8500
• Description: PWM Buck Converters with Bypass FET for N-CDMA/W-CDMA Handsets
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX8500–MAX8504 PWM step-down DC-to-DC
converters with integrated bypass PFET are optimized
for low-voltage, battery-powered applications where high
efficiency and small size are priorities (such as linear PA
applications). An analog control signal dynamically
adjusts the MAX8500–MAX8503s’ output voltage from
0.4V to V
MAX8504 uses external feedback resistors to set the out-
put voltage from 1.25V to 2.5V.
The MAX8500–MAX8504 operate at a high 1MHz
switching frequency that reduces external component
MAX8500–
MAX8503
5, 9
—
—
10
11
12
1
2
3
4
6
7
8
BATT
PIN
with a settling time <30µs (Figure 1). The
MAX8504
_______________________________________________________________________________________
10
11
12
—
1
2
3
4
9
5
6
7
8
PWM Buck Converters with Bypass FET
Detailed Description
BATTP
NAME
COMP
REFIN
PGND
SHDN
BATT
GND
SKIP
OUT
REF
HP
FB
LX
Ground
Reference Bypass Pin. Connect a 0.22µF ceramic capacitor from this pin to GND.
External Reference Input. Connect REFIN to the output of a DA converter for dynamic
adjustment of the output voltage.
Output Feedback Sense Input. To set the output voltage, connect FB to the center of an
external resistive voltage-divider between OUT and GND. FB voltage regulates to 1.25V
when HP is logic 0.
Compensation. Connect a series resistor and capacitor from this pin to GND to stabilize
the regulator (see the Compensation, Stability, and Output Capacitor section).
IC Supply Voltage Input. Connect to BATTP.
High-Power Bypass Mode. Connect to GND or logic 0 for OUT to regulate to the voltage
set by the external resistors on FB. Drive with logic 1 for OUT to be connected to BATT
through the internal bypass PFET.
Power Ground
Inductor Connection to the Drains of the Internal Power MOSFETs. High impedance in
shutdown mode.
Power-Supply Voltage Input. Connect to a 2.6V to 5.5V source. Bypass with a low-ESR
10µF capacitor.
Regulator Output. Connect OUT directly to the output voltage.
Skip Control Input. Connect to GND or logic 0 for normal mode. Connect to BATT or logic
1 for forced-PWM mode.
Shutdown Control Input. Connect to GND or logic 0 for shutdown mode. Connect to BATT
or logic 1 for normal operation.
for N-CDMA/W-CDMA Handsets
size. Each device includes an internal synchronous rec-
tifier that provides for high efficiency and eliminates the
need for an external Schottky diode. The normal operat-
ing mode uses constant-frequency PWM switching at
medium and heavy loads, and automatically pulse skips
at light loads to reduce supply current and extend bat-
tery life. An additional forced-PWM mode switches at a
constant frequency, regardless of load, to provide a
well-controlled spectrum in noise-sensitive applications.
Battery life is maximized by low-dropout operation at
100% duty cycle and a 0.1µA (typ) logic-controlled shut-
down mode.
FUNCTION
Pin Description
7