Document
HT77XXA PFM Step-up DC/DC Converter
Features
· Low start-up voltage: 0.7V (Typ.) · High efficiency: 85% (Typ.) · High output voltage accuracy: ±2.5% · Output voltage: 2.7V, 3.0V, 3.3V, 5.0V
· Ultra low supply current IDD: 5mA (Typ.) · Low ripple and low noise
· Low shutdown current: 0.5mA (Typ.) · TO-92, SOT-89, SOT-23 and SOT-25 package
Applications
· Palmtops/PDAs · Portable communicators/Smartphones
· Cameras/Camcorders · Battery-powered equipment
General Description
The HT77XXA series is a set of PFM step-up DC/DC converter with high efficiency and low ripple. The series features extremely low start-up voltage and high output voltage accuracy. They require only three external components to provide a fixed output voltage of 2.7V, 3.0V, 3.3V or 5.0V. CMOS technology ensures ultra low supply current and makes them ideal for battery-operated applications powered from one or more cells.
The HT77XXA consists of an oscillator, a PFM control circuit, a driver transistor, a reference voltage unit, and a high speed comparator. They employ pulse frequency modulation (PFM) for minimum supply current and ripple at light output loading. These devices are available in space saving TO-92, SOT-89, SOT-23 and SOT-25 packages. For SOT-25 package, it also build-in a chip enable function to reduce power consumption during shutdown mode.
Selection Table
Part No. HT7727A HT7730A HT7733A HT7750A
Output Voltage 2.7V 3.0V 3.3V 5.0V
Package
TO-92 SOT-89 SOT-23 SOT-25
Marking
HT77XXA (for TO-92) HT77XXA# (for SOT-89)
77XXA# (for SOT-23) 77XXA# (for SOT-25)
Note: ²XX² stands for output voltages.
Only lead free devices are available. ²#² stands for lead free devices. For the TO-92 package, there will be a ²#² mark at the end of the date code.
Block Diagram
L X L X L im ite r O S C 2 0 0 k H z
VO UT V re f
B u ffe r
P F M C o n tro l
C h ip E n a b le CE
GND
Rev 1.10
1 September 26, 2007
HT77XXA
Pin Assignment
T O -9 2
S O T -8 9
H T77X X A 123
F r o n t V ie w
H T77X X A #
S O T -2 3
VO UT 3
T o p V ie w
77X X A #
S O T -2 5
LX 5
GND 4
T o p V ie w
77X X A #
T o p V ie w
G N D V O U T LX
1 23 G N D V O U T LX
12 G N D LX
1 23 CE VO UT NC
B o tto m V ie w G N D V O U T LX
G N D LX
CE VO UT NC
Pin Description
TO-92
Pin No.
SOT-89
SOT-23
¾¾¾
223
¾¾¾
111
332
SOT-25 1 2 3 4 5
Pin Name
Description
CE VOUT
NC GND LX
Chip enable pin, high active DC/DC converter output monitoring pin No connection Ground pin Switching pin
Absolute Maximum Ratings
Supply Voltage ..............................VSS-0.3V to VSS+7V Operating Temperature ...........................-40°C to 85°C
Storage Temperature ............................-50°C to 125°C
Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maximum Ratings² may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability.
Thermal Information
Symbol
Parameter
Thermal Resistance
qJA
(Junction to Ambient) (Assume no ambient airflow,
no heat sink)
PD Power Dissipation Note: PD is measured at Ta= 25°C
Package SOT-89 TO-92 SOT-23 SOT-25 SOT-89 TO-92 SOT-23 SOT-25
Max. 300 300 330 320 0.33 0.33 0.3 0.31
Unit °C/W °C/W °C/W °C/W
W W W W
Rev 1.10
2 September 26, 2007
HT77XXA
Electrical Characteristics
VIN=VOUT´0.6; IOUT=10mA; Ta=25°C (Unless otherwise specified)
Symbol
Parameter
Test Conditions
Min. Typ. Max. Unit
VIN VOUT
Input Voltage Output Voltage Tolerance
¾ ¾¾ 6 V ¾ -2.5 ¾ 2.5 %
VSTART VHOLD IIN IDD
ISHDN
Start-up Voltage (Fig. 1)
VIN: 0®2V; IOUT=1mA
Minimum Hold-on Voltage (Fig. 1) VIN: 2®0V; IOUT=1mA
No-load Input Current (Fig. 1) IOUT=0mA
Supply Current (Fig. 2)
VS=VOUT+0.5V Measured at VOUT pin
Shutdown Current
CE=GND
¾ 0.7 0.9 V ¾ ¾ 0.7 V ¾ 13 26 mA
¾ 5 10 mA
¾ 0.5 1 mA
VIH CE High Threshold
¾ 2 ¾¾ V
VIL CE Low Threshold
¾ ¾ ¾ 0.4 V
ILEAK
LX Leakage Current (Fig. 3)
VS=VOUT+0.5V, VX=6V Measured at the LX pin
¾ ¾ 0.9 mA
fOSC
Maximum Oscillator Frequency VS=VOUT´0.95, VX=6V
(Fig. 3)
Measured at LX pin
¾ 200 ¾ kHz
DOSC
Oscillator Duty Cycle (Fig. 3)
VS=VOUT´0.95, VX=6V Measured at LX pin
65 75 85 %
h Efficiency
¾ ¾ 85 ¾ %
Note: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. The guaranteed specifications apply only for the test conditions listed.
Test Circuit
100mH V IN
1N 5817
V OUT
47mF LX ( T a n ta lu m )
VO UT H T77X X A
S e r ie s
GND
(F ig . 1 )
22mF V S ( T a n ta lu m )
VO UT
LX
H T77X X A
S e r ie s
GND
VS
VO UT
LX
H T77X X A
S e r ie s
GND
100W VX
(F ig . 2 )
(F ig . 3 )
Rev 1.10
3 September 26, 2007
HT77XXA
Typical Performance Characteristics
O u tp u t V o lta g e ( V )
2 .8.