Rainbow Electronics MAX8902B - Manual (Page 5)

Detailed Description
The MAX8902A/MAX8902B low-noise, low-dropout lin-
ear regulators deliver up to 500mA of output current
with only 16µV
RMS of output noise in a 100kHz band-
width. These regulators maintain their output voltage
over a wide input range, requiring only 100mV of input-
to-output headroom at full load.
The MAX8902 maintains a low 80µA typical supply cur-
rent, independent of the load current and dropout volt-
age. The regulator control circuitry includes a
programmable soft-start circuit and short circuit,
reverse current, and thermal-overload protection. Other
features include an enable input and a power-OK
(POK) output (MAX8902B only). A simplified functional
diagram is shown in Figure 1.
The MAX8902A output voltage can be set to 1.5V, 1.8V,
2.0V, 2.5V, 3.0V, 3.1V, 3.3V, 4.6V, or 4.7V using the
SELA and SELB inputs. The MAX8902B output voltage
can be set between 0.6V and 5.3V with an external
resistor voltage-divider.
Enable (EN)
The MAX8902A/MAX8902B include an enable input,
EN. Pull EN low to shut down the output, or drive EN
high to enable the output. If shutdown is not needed,
connect EN to IN.
MAX8902A/MAX8902B
Low-Noise 500mA LDO Regulators
in a 2mm x 2mm TDFN Package
_______________________________________________________________________________________ 5
Pin Description
NAME
PIN
MAX8902A MAX8902B
FUNCTION
1 IN IN
Regulator Power Input. Connect IN to a supply from 1.7V to 5.5V. Bypass IN with a 10µF
ceramic capacitor to GND.
2 GND GND Ground
3 EN EN
Enable Input. A logic-low drives the output low through a 3k Ω resistor and reduces the
supply current to less than 1µA. Drive logic-high or connect to IN for normal operation.
SELA —
Output Voltage Select Input. Connect SELA to GND, IN, or leave unconnected. The states of
SELA and SELB are sampled when the regulator turns on and the output voltage is set as
shown in Table 2.
4
— GS Internally Used. Connect GS to GND.
SELB —
Output Voltage Select Input. Connect SELB to GND, IN, or leave unconnected. The states of
SELA and SELB are sampled when the regulator turns on and the output voltage is set as
shown in Table 2.
5
— POK
Power-OK Output. Open-drain output that goes low when the output is above 91% of the
nominal regulation voltage. POK is high impedance in shutdown or when the output is below
the regulation voltage.
OUTS —
Output Sense Input. Connect OUTS to the load at a point where accurate regulation is
required, or connect OUTS directly to OUT.
6
— FB
Feedback Input. Connect FB to the center of a resistor voltage-divider connected between
OUT and GND to set the output voltage. V
FB regulates to 0.6V.
7 BYP BYP
Bypass Input. Connect a 0.01µF ceramic capacitor from BYP to OUT to achieve 16µV RMS
output noise. Adjust the value of this capacitor to control the output slew rate during startup.
Slew Rate = (5V / ms) x (0.01µF / C
BYP
)
8 OUT OUT
Regulator Output. Sources up to 500mA at the output regulation voltage. Bypass with a 10µF
(< 0.03
Ω ESR) capacitor to GND.
— EP EP Exposed Paddle. Connect the exposed paddle to a ground plane to provide heat sinking.