Rainbow Electronics MAX1976 - Manual (Page 8)

MAX1963/MAX1976
The MAX1963/MAX1976 deliver up to 300mA and oper-
ate with an input voltage up to +3.6V. However, when
using the 6-pin SOT23 version, high output currents
can only be sustained when the input-output differential
voltage is less than 2V, as shown in Figure 2.
The maximum allowed power dissipation for the 6-pin
TDFN is 1.951W at T
A = +70°C. Figure 3 shows that the
maximum input-output differential voltage is not limited
by the TDFN package power rating.
Applications Information
Capacitor Selection and
Regulator Stability
Capacitors are required at the MAX1963/MAX1976
input and output for stable operation over the full tem-
perature range and with load currents up to 300mA.
Connect a 1µF ceramic capacitor between IN and GND
and a 4.7µF low-ESR ceramic capacitor between OUT
and GND. The input capacitor (C
IN ) lowers the source
impedance of the input supply. Use larger output
capacitors to reduce noise and improve load-transient
response, stability, and power-supply rejection.
The output capacitor’s equivalent series resistance
(ESR) affects stability and output noise. Use output
capacitors with an ESR of 30m
Ω or less to ensure sta-
bility and optimize transient response. Surface-mount
ceramic capacitors have very low ESR and are com-
monly available in values up to 10µF. Connect C
IN and
C OUT as close to the MAX1963/MAX1976 as possible
to minimize the impact of PC board trace inductance.
Noise, PSRR, and Transient Response
The MAX1963/MAX1976 are designed to operate with
low dropout voltages and low quiescent currents in bat-
tery-powered systems while still maintaining good
noise, transient response, and AC rejection. See the
Typical Operating Characteristics for a plot of Power-
Supply Rejection Ratio (PSRR) versus Frequency.
When operating from noisy sources, improved supply-
noise rejection and transient response can be achieved
by increasing the values of the input and output bypass
capacitors and through passive filtering techniques.
The MAX1963/MAX1976 load-transient response (see
the Typical Operating Characteristics) shows two com-
ponents of the output response: a near-zero DC shift
from the output impedance due to the load-current
change, and the transient response. A typical transient
response for a step change in the load current from 20mA
to 200mA is 20mV. Increasing the output capacitor’s value
and decreasing the ESR attenuates the overshoot.
Input-Output (Dropout) Voltage
A regulator’s minimum input-output voltage difference
(dropout voltage) determines the lowest usable supply
voltage. In battery-powered systems, this determines the
useful end-of-life battery voltage. Because the
MAX1963/MAX1976 use a P-channel MOSFET pass tran-
sistor, the dropout voltage is a function of drain-to-source
on-resistance (R
DS(ON) = 0.33 Ω) multiplied by the load
current (see the Typical Operating Characteristics).
V DROPOUT = V IN - V OUT = 0.33 Ω ✕ I OUT
The MAX1963/MAX1976 ground current reduces to 70µA
in dropout.
Low-Input-Voltage, 300mA LDO Regulators
with
RESET
in SOT and TDFN
8 _______________________________________________________________________________________
Chip Information
TRANSISTOR COUNT: 2556
PROCESS: BiCMOS
MAX1963
TOP MARK
MAX1976
TOP MARK
V OUT
(V)
SUFFIX
SOT TDFN SOT TDFN
0.75 075 AABA AFQ AAAQ AGA
0.85 085 — — AABP AHD
1.00 100 — — AABL AGC
1.10 110 — — AABM AGD
1.20 120 AABE AFU AAAK AGE
1.30 130 AABF AFV AABN AGF
1.50 150 AABG AFW AAAL AGG
1.60 160 — — AABO AHC
1.80 180 AABH AFX AAAM AGH
2.50 250 AABI AFY AAAN AGI
2.85 285 — — AAAO AGJ
3.00 300 AABJ AFZ AAAP AGK
Selector Guide