H9008
1.5A Synchronous Step-Down Converter
Features
High Efficiency: Up to 96%
2.5V to 6V Input Voltage Range
1.5MHz Constant Frequency Operation
No Schottky Diode Required
Low Dropout Operation:100% Duty
Cycle
PFM Mode for High Efficiency in Light Load
Over temperature Protected
Low Quiescent
Current: 40μA
Short Circuit Protection
Inrush Current Limit and Soft Start
SOT23-5 package
Applications
Cellular and Smart Phones
Wireless and DSL Modems
PDAs
Portable Instruments
Digital Still and Video Cameras
PC Cards
General Description
The
H9008
is
a
high-efficiency
monolithic
operation provides very low output ripple voltage
synchronous buck regulator using a constant
frequency, current mode architecture. The device
is available in an adjustable version. Supply
current with no load is 40uA and drops to <1uA in
shutdown. The 2.5V to 6V input voltage range
IN
for
noise
sensitive
adjustable version.
applications.Switching
frequency is internally set at 1.5MHz, allowing the
use of small surface mount inductors and
capacitors. Low output voltages
are easily
supported with the 0.6V feedback reference
makes the H9008 ideally suited for single Li-Ion
battery powered applications. 100% duty cycle
provides low dropout operation, extending battery
life
in
portable
systems.
PWM/PFM
mode
Selection Table
SI
H9008
Ver1.5
PR
1
O
voltage.The H9008 is offered in a low profile (1mm)
5-pin, thin SOT package, and is available in an
Shanghai Siproin Microelectronics Co.
H9008
1.5A Synchronous Step-Down Converter
Functional Block Diagram
EN
VIN
RS
OSC &
Shutdown
Control
Slope
Compensation
Current
Sensor
Current Limit
Detector
PWM/PFM
Mode
Detector
FB
Error
Amplifier
PWM
Compartor
Control Logic
Driver
SW
Zero Detector
UVLO & Power
Good Detector
VREF
GND
Figure 1. H9008 Block Diagram
Package/order Information
EN
GND
SW
1
2
3
PR
NAME
EN
GND
Ground Pin
SW
VIN
FB
reference voltage.
O
4
VIN
(SOT23-5)
FUNCTION
SI
PIN
1
2
3
4
5
Pin Description
Chip Enable Pin. Drive EN above 1.5V to turn on the part.
Drive EN below 0.3V to turn it off. Do not leave EN floating.
Power Switch Output. It is the switch node connection to
Inductor. This pin connects to the drains of the internal P-ch and
N-ch MOSFET switches.
Power Supply Input. Must be closely decoupled to GND with a
10µF or greater ceramic capacitor.
Output Voltage Feedback Pin. An internal resistive divider
divides the output voltage down for comparison to the internal
Ver1.5
IN
5
FB
2
Shanghai Siproin Microelectronics Co.
H9008
1.5A Synchronous Step-Down Converter
Absolute Maximum Ratings
(Note 1)
Input Supply Voltage ····················································································· -0.3V to 6.0V
Operating Temperature Range ········································································-40℃ to +85℃
EN, FB Voltages ··························································································· -0.3V to 6.0V
Junction Temperature
(Note2)
····················································································· 125℃
SW Voltage ···························································································-0.3V to (Vin+0.3V)
Storage Temperature Range ········································································ -65℃ to 150℃
Peak SW Sink and Source Current ············································································· 2 A
Lead Temperature(Soldering,10s) ··········································································· +300℃
Electrical Charcteristics
(Note 3)
(VIN=VEN=3.6V, TA = 25°C, unless otherwise noted.)
Parameter
Input Voltage Range
UVLO Threshold
Conditions
MIN
2.5
TYP
MAX
6.0
unit
V
V
2.4
FB = 90%, Iload=0mA
150
40
0.1
300
70
1.0
0.612
0.40
0.4
µA
µA
µA
V
%/V
%
%
MHz
Ω
Ω
Input DC Supply Current
FB= 105%, Iload=0mA
VEN = 0V, VIN=4.2V
Regulated Feedback Voltage
TA = 25°C
Reference Voltage Line Regulation Vin = 2.5V to 6.0V
Output Voltage Line Regulation
Output Voltage Load Regulation
Oscillation Frequency
On Resistance of PMOS
O
0.30
VIN = 2.5V to 6.0V
PR
ISW=100mA
ISW=-100mA
VIN= 3.6V, FB=90%
VEN=0V,VIN=Vsw=5V
ON Resistance of NMOS
Peak Current Limit
EN Threshold
IN
0.588
0.600
0.04
0.04
0.5
1.5
0.3
0.2
1.0
±0.01
±0.01
160
2
1.50
±1.0
±1.0
A
V
µA
µA
℃
SW Leakage Current
Thermal Shutdown
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula:
TJ = TA + (PD) x (250°C/W).
Note3: 100% production test at +25° C.
characterization.
Specifications over the temperature range are guaranteed by design and
Operation
The H9008 uses a constant frequency, current mode step-down architecture. Both the main (P-channel
MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the
internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off
when the current comparator, ICOMP, resets the RS latch. The peak inductor current at which ICOMP
resets the RS latch, is controlled by the output of error amplifier EA. When the load current increases, it
causes a slight decrease in the feedback voltage, FB, relative to the 0.6V reference, which in turn,
causes the EA amplifier’s output voltage to increase until the average inductor current matches the new
load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor
SI
EN Leakage Current
Ver1.5
3
Shanghai Siproin Microelectronics Co.
H9008
1.5A Synchronous Step-Down Converter
current starts to reverse, as indicated by the current reversal comparator IRCMP, or the beginning of the
next clock cycle.
Typical Performance Characteristics
Applications Information
Setting the Output Voltage
In the adjustable version, the output voltage is set by a resistive divider according to the following
formula:
R
2
=
R
1
/
V
FB
−
1
SI
V
out
Ver1.5
PR
4
Shanghai Siproin Microelectronics Co.
O
IN
H9008
1.5A Synchronous Step-Down Converter
The external resistive divider is connected to the output, allowing remote voltage sensing as shown in on
page 1 .
Inductor Selection
For most designs, the H9008 operates with inductors of 1µH to 4.7µH. Low inductance values are
physically smaller but require faster switching, which results in some efficiency loss. The inductor value
can be derived from the following equation:
L
=
V
OUT
×
(
V
IN
−
V
OUT
)
V
IN
× ∆
I
L
×
f
OSC
Where
∆
I
L
is inductor Ripple Current. Large value inductors result in lower ripple current and small
value inductors result in high ripple current. For optimum voltage-positioning load transients, choose an
inductor with DC series resistance in the 50mΩ to 150mΩ range.
Input Capacitor Selection
Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their
high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications.
Because the H9008’s control loop does not depend on the output capacitor’s ESR for stable operation,
ceramic capacitors can be used freely to achieve very low output ripple and small circuit size. However,
care must be taken when ceramic capacitors are used at the input and the output. When a ceramic
capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step
mistaken as loop instability. At worst, a sudden inrush of current through the long wires can potentially
cause a voltage spike at VIN, large enough to damage the part. When choosing the input and output
temperature and voltage characteristics of all the ceramics for a given value and size.
PC Board Layout Checklist
When laying out the printed circuit board, the following checking should be used to ensure proper
operation of the H9008. Check the following in your layout:
direct and wide.
2.
3.
4.
1.
The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short,
Does the (+) plates of Cin connect to Vin as closely as possible? This capacitor provides the AC
current to the internal power MOSFETs.
Keep the switching node, SW, away from the sensitive VOUT node.
Keep the (-) plates of Cin and Cout as close as possible.
ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best
at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be
SI
Ver1.5
PR
5
O
IN
Shanghai Siproin Microelectronics Co.
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