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參數(shù)資料
| 型號： | 935261695112 |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.25 A SWITCHING REGULATOR, 50 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOT-176, 8 PIN |
| 文件頁數(shù)： | 20/22頁 |
| 文件大?。?/td> | 154K |
| 代理商： | 935261695112 |
1998 Aug 19
7
Philips Semiconductors
Preliminary specication
Greeny; GreenChip
TEA1501
CIRCUIT BLOCK DESCRIPTION
On/Off/Data section
The On/Off/Data block contains a comparator for the on/off
level and is active if the drain voltage is above 50 V (DC).
The typical current consumption in Off mode is 40
A. The
data signal changes the clamp level on the OOD pin to
indicate data transfer: low clamp level for data-off and high
clamp level for data-on.
Vaux management
The Vaux management block is active when Greeny is in
the On mode. This Vaux management block senses the
Vaux voltage and determines the state of Greeny: startup
or normal operation. During startup the following circuits
are active: On/Off/Data section, Reference block (partial),
Vaux management, Temperature protection and the
Startup current source.
Fig.5 IVaux versus VVaux.
handbook, halfpage
MGM824
20 V
16 V
12 V
UVLO
Vstart
VVaux(max) VVaux
startup
operation
IVaux
Istart
Startup current source
The startup sequence is carried out using an accurate
startup current source. The startup current flows from the
Drn pin to the Vaux pin via the startup current source and
charges the Vaux capacitor. When Vaux reaches the
startup threshold the startup current is switched off and the
flyback converter starts operating and the output voltage
rises. The Vaux capacitor must be capable of supplying
the entire supply current (IVaux(LOW)) until the output
voltage is in regulation. From that moment the Vaux
capacitor is charged by the flyback converter via the
auxiliary winding.
Reference block
The reference block contains a bandgap circuit which
determines all the accurate and temperature independent
reference voltages and currents. It defines the voltage
detection level for the primary current comparator and it
defines the voltage at the Ref pin. The value of the
reference resistor determines the burst frequency, the
switching frequency and the leading edge blanking time.
Temperature protection
The temperature protection circuit senses the chip
temperature using a proportional to absolute temperature
voltage (Vptat) generated in the reference block. If the chip
temperature exceeds 140
°C the power switch and the
startup current source are disabled. When the chip cools
down below 100
°C, the startup circuit is enabled again.
Switch oscillator
The switch oscillator determines the switching frequency
and the maximum on-time of the power switch. The
maximum on-time is set at 66% of the switching period.
The switching frequency is determined by the reference
resistor at the Ref pin and an internal capacitor. The
switching frequency can be adjusted in a range from
20 to 50 kHz, thus above the audible spectrum.
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