Synchronous Buck Controller with Constant
On-Time and Valley Current Mode
ADP1874/ADP1875
FEATURES
TYPICAL APPLICATIONS CIRCUIT
V
= 2.95V TO 20V
IN
Power input voltage range: 2.95 V to 20 V
On-board bias regulator
Minimum output voltage: 0.6 V
VIN
C
C
ADP1874/
ADP1875
C
IN
C
C2
0.6 V reference voltage with 1.0% accuracy
Supports all N-channel MOSFET power stages
Available in 300 kHz, 600 kHz, and 1.0 MHz options
No current-sense resistor required
R
C
COMP
BST
DRVH
SW
C
Q1
BST
10kΩ
L
VREG
EN
FB
V
R
OUT
TOP
V
OUT
C
Q2
OUT
R
LOAD
BOT
Power saving mode (PSM) for light loads (ADP1875 only)
Resistor programmable current limit
Power good with internal pull-up resistor
Externally programmable soft start
Thermal overload protection
GND
DRVL
C
VREG2
R
PGD
VREG
PGOOD
V
EXT
C
VREG
VREG_IN
RES
SS
C
SS
R
TRK2
R
RES
TRACK
PGND
V
MASTER
R
TRK1
Short-circuit protection
Standalone precision enable input
Integrated bootstrap diode for high-side drive
Starts into a precharged output
Figure 1. Typical Applications Circuit
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
Available in a 16-lead QSOP package
V
= 5V (PSM)
IN
APPLICATIONS
Telecom and networking systems
Mid- to high-end servers
Set-top boxes
V
= 16.5V
IN
V
= 13V
DSP core power supplies
IN
V
= 13V (PSM)
IN
GENERAL DESCRIPTION
T
= 25°C
A
V
= 1.8V
OUT
= 300kHz
The ADP1874/ADP1875 are versatile current mode, synchronous
step-down controllers. They provide superior transient response,
optimal stability, and current-limit protection by using a constant
on-time, pseudo fixed frequency with a programmable current
limit, current control scheme. In addition, these devices offer
optimum performance at low duty cycles by using a valley, current
mode control architecture. This allows the ADP1874/ADP1875
to drive all N-channel power stages to regulate output voltages
to as low as 0.6 V.
f
SW
V
= 16.5V (PSM)
IN
WÜRTH INDUCTOR:
744325120, L = 1.2µH, DCR = 1.8mꢀ
INFINEON FETs:
BSC042N03MS G (UPPER/LOWER)
10
100
1k
10k
100k
LOAD CURRENT (mA)
Figure 2. ADP1874/ADP1875 Efficiency vs. Load Current (VOUT = 1.8 V, 300 kHz)
In addition, soft start programmability is included to limit input in-
rush current from the input supply during startup and to
provide reverse current protection during precharged output
conditions. The low-side current sense, current gain scheme, and
integration of a boost diode, along with the PSM/forced pulse-
width modulation (PWM) option, reduce the external part count
and improve efficiency.
The ADP1875 is the power saving mode (PSM) version of
the device and is capable of pulse skipping to maintain output
regulation while achieving improved system efficiency at light
loads (see the ADP1875 Power Saving Mode (PSM) section for
more information).
The ADP1874/ADP1875 operate over the −40°C to +125°C
junction temperature range and are available in a 16-lead QSOP
package.
Available in three frequency options (300 kHz, 600 kHz, and
1.0 MHz, plus the PSM option), the ADP1874/ADP1875 are well
suited for a wide range of applications that require a single-input
power supply range from 2.95 V to 20 V. Low voltage biasing is
supplied via a 5 V internal low dropout regulator (LDO).
Rev. 0
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