ADP1612 데이터 시트보기 (PDF) - Analog Devices
부품명
상세내역
제조사
ADP1612 Datasheet PDF : 28 Pages
| |||
Data Sheet
ADP1612/ADP1613
THEORY OF OPERATION
VIN
L1
CIN
VIN
6
>1.6V
<0.3V
FREQ
7
+
VIN
D
+
COMPARATOR
VOUT
R1
FB
2
ERROR
AMPLIFIER
PWM
COMPARATOR
R2
VBG
COMP
1
UVLO
COMPARATOR
VIN
RCOMP
CCOMP
CSS
SS
8
VSS
5µA
UVLOREF
TSD
COMPARATOR
TSENSE
SOFT
START
TREF
DREF
OSCILLATOR
RESET
S
Q
R
BG
A
CURRENT
SENSING
5µA
DRIVER
BAND GAP
SW
D1
5
N1
1.1MΩ
ADP1612/AD1613
AGND
VOUT
COUT
AGND
3
EN
>1.6V
<0.3V
4
GND
Figure 34. Block Diagram with Step-Up Regulator Application Circuit
The ADP1612/ADP1613 current-mode step-up switching
converters boost a 1.8 V to 5.5 V input voltage to an output
voltage as high as 20 V. The internal switch allows a high
output current, and the high 650 kHz/1.3 MHz switching
frequency allows for the use of tiny external components.
The switch current is monitored on a pulse-by-pulse basis to
limit it to 1.4 A typical (ADP1612) or 2.0 A typical (ADP1613).
CURRENT-MODE PWM OPERATION
The ADP1612/ADP1613 utilize a current-mode PWM control
scheme to regulate the output voltage over all load conditions.
The output voltage is monitored at FB through a resistive voltage
divider. The voltage at FB is compared to the internal 1.235 V
reference by the internal transconductance error amplifier to
create an error voltage at COMP. The switch current is internally
measured and added to the stabilizing ramp. The resulting sum
is compared to the error voltage at COMP to control the PWM
modulator. This current-mode regulation system allows fast
transient response, while maintaining a stable output voltage.
By selecting the proper resistor-capacitor network from COMP
to GND, the regulator response is optimized for a wide range of
input voltages, output voltages, and load conditions.
FREQUENCY SELECTION
The frequency of the ADP1612/ADP1613 is pin-selectable
to operate at either 650 kHz to optimize the regulator for high
efficiency or at 1.3 MHz for use with small external components.
If FREQ is left floating, the part defaults to 650 kHz. Connect
FREQ to GND for 650 kHz operation or connect FREQ to VIN
for 1.3 MHz operation. When connected to VIN for 1.3 MHz
operation, an additional 5 μA, typical, of quiescent current is
active. This current is turned off when the part is shutdown.
SOFT START
To prevent input inrush current to the converter when the part is
enabled, connect a capacitor from SS to GND to set the soft start
period. Once the ADP1612/ADP1613 are turned on, SS sources
5 µA, typical, to the soft start capacitor (CSS) until it reaches
1.2 V at startup. As the soft start capacitor charges, it limits the
peak current allowed by the part. By slowly charging the soft
start capacitor, the input current ramps slowly to prevent it
from overshooting excessively at startup. When the ADP1612/
ADP1613 are in shutdown mode (EN ≤ 0.3 V), a thermal shut-
down event occurs, or the input voltage is below the falling
undervoltage lockout voltage, SS is internally shorted to GND
to discharge the soft start capacitor.
Rev. D | Page 11 of 28
Share Link: 