Datasheet

ADP1607 Data Sheet
Rev. C | Page 10 of 16
THEORY OF OPERATION
SW
+
+
VIN
N
RESET
AGND
GND
T
SENSE
T
REF
1
V
DD
L1
A
V
OUT
C
OUT
5
2
4
EN
V
IN
S
R
QP
QN
RP
V
SEL
SW
P
6
V
SEL
V
IN
OFF
ON
3
FB
R1
R2
V
OUT
C
IN
V
REF
PFM
COMPARATOR
PWM
COMPARATOR
CURRENT-LIMIT
COMPARATOR
TSD
COMPARATOR
PFM
CONTROL
SHUTDOWN
ZERO
CROSS
PMOS
BULK
CONTROL
P DRIVER
CURRENT
SENSING
N DRIVER
OSCILLATOR
SOFT
START
R
COMP
C
COMP
ERROR
AMPLIFIER
V
REF
BULK
CONTROL
V
OUT
10276-033
Figure 24. Block Diagram
OVERVIEW
The ADP1607 is a high efficiency, synchronous, fixed
frequency, step-up dc-to-dc switching converter with an
adjustable output voltage between 1.8 V and 3.3 V for use
in portable applications.
The 2 MHz operating frequency enables the use of small
footprint, low profile external components. Additionally, the
synchronous rectification, internal compensation, internal fixed
current limit, and current-mode architecture allow for excellent
transient response and a minimal external part count. Other
key features include fixed PWM and light load PFM mode
options, true output isolation, thermal shutdown (TSD), and
logic controlled enable.
ENABLE/SHUTDOWN
The EN input turns the ADP1607 on or off. Connect EN to
GND or logic low to shut down the part and reduce the current
consumption to 0.06 µA (typical). Connect EN to VIN or logic
high to enable the part. Do not exceed V
IN
. Do not leave this pin
floating.
MODES OF OPERATION
The ADP1607 is available in a fixed PWM mode only option
for noise sensitive applications or in an auto PFM-to-PWM
transitioning mode option to optimize power at light loads.
Pulse-Width Modulation (PWM) Mode
The PWM version of the ADP1607 utilizes a current-mode
PWM control scheme to force the part to maintain a fixed
2 MHz fixed frequency while regulating the output voltage over
all load conditions. The auto mode version of the ADP1607
operates in PWM for higher load currents. In PWM, the output
voltage is monitored at the FB pin through the external resistive
voltage divider. The voltage at FB is compared to the internal
1.259 V reference by the internal error amplifier. This current-
mode PWM regulation system allows fast transient response
and tight output voltage regulation. PWM mode operation
results in lower efficiencies than PFM mode at light loads.
Auto Mode
Auto mode is a power-saving feature that forces the auto version
of the ADP1607 to switch between PFM and PWM in response
to output load changes. The auto version of the ADP1607