SP6200 Datasheet, PDF (6/17 Pages) Sipex Corporation – Micropower, 100mA and 200mA CMOS LDO Regulators

THEORY OF OPERATION
General Overview
The SP6200 and SP6201 are CMOS LDOs
designed to meet a broad range of applications
that require accuracy, speed and ease of use.
These LDOs offer extremely low quiescent cur-
rent which only increases slightly under load,
thus providing advantages in ground current
performance over bipolar LDOs. The LDOs
handle an extremely wide load range and guar-
antee stability with a 1µF ceramic output ca-
pacitor. They have excellent low frequency
PSRR, not found in other CMOS LDOs and thus
offer exceptional Line Regulation. High fre-
quency PSRR is better than 40dB up to 400kHz.
Load Regulation is excellent and temperature
stability is comparable to bipolar LDOs. Thus,
overall system accuracy is maintained under all
DC and AC conditions. Enable feature is pro-
vided on all versions. A Vout good indicator
(RSN pin) is provided in all the fixed output
voltage devices. An adjustable output version is
also available. Current Limit and Thermal pro-
tection is provided internally and is well con-
trolled.
Architecture
The SP6200 and SP6201 are only different in
their current limit threshold. The SP6200 has a
current limit of 140mA, while the SP6201 cur-
rent limit is 420mA. The SP6201 can provide
pulsed load current of 300mA. The LDOs have
a two stage amplifier which handles an ex-
tremely wide load range (10µA to 300mA) and
guarantees stability with a 1µF ceramic load
capacitor. The LDO amplifier has excellent gain
and thus touts PSRR performance not found in
other CMOS LDOs. The amplifier guarantees
no overshoot on power up or while enabled
through the EN pin. The amplifier also contains
an active pull down, so that when the load is
removed quickly the output voltage transient is
minimal; thus output deviation due to load tran-
sient is small and fairly well matched when
connecting and disconnecting the load.
An accurate 1.250V bandgap reference is
bootstrapped to the output in fixed output ver-
sions of 2.7V and higher. This increases both the
low frequency and high frequency PSRR. The
adjustable version also has the bandgap refer-
ence bootstrapped to the output, thus the lowest
externally programmable output voltage is 2.7V.
The 2.5V fixed output version has the bandgap
always connected to the Vin pin. Unlike many
LDOs, the bandgap reference is not brought out
for filtering by the user. This tradeoff was maid
to maintain good PSRR at high frequency (PSRR
can be degraded in a system due to switching
noise coupling into this pin). Also, often leak-
ages of the bypass capacitor or other compo-
nents cause an error on this high impedance
bandgap node. Thus, this tradeoff has been
made with "ease of use" in mind.
Protection
Current limit behavior is very well controlled,
providing less than 10% variation in the current
limit threshold over the entire temperature range
for both SP6200 and SP6201. The SP6200 has a
current limit of 140mA, while the SP6201 has a
current limit of 420mA. Thermal shutdown ac-
tivates at 162°C and deactivates at 147°C. Ther-
mal shutdown is very repeatable with only a 2 to
3 degree variation from device to device. Ther-
mal shutdown changes by only 1 to 2 degrees
with Vin change from 4V to 7V.
Enable (Shutdown Not) Input
The LDOs are turned off by pulling the EN pin
low and turned on by pulling it high. If it is not
necessary to shut down the LDO, the EN (pin 3)
should be tied to IN (pin 1) to keep the regulator
output on at all time. The enable threshold is
0.9V and does not change more than 100mV
over the entire temperature and Vin voltage
range. The lot to lot variations in Enable Thresh-
old is also within 100mV. Shutdown current is
guaranteed to be <1uA without requiring the
user to pull enable all the way to 0V. Standard
TTL or CMOS levels will transition the device
from totally on to totally off.
Date:5/25/04
SP6200/6201 100/200mA CMOS LDO Regulator
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© Copyright 2004 Sipex Corporation