ST AN1707 APPLICATION NOTE
1 INTRODUCTION
APPLICATION NOTE
AN1707
TD220/221
Gate Driver wit h Vreg and Two-Point Regulator
by Giuseppe Scuderi
This application note gives a simple functional
description of the TD220/221, which is a standard
circuit designed with an industrial application in
mind, see
However, the TD220/221, together with other ST
components, such as an ST7 microcontroller, and
a MOSFET device, can provide a flexible, highperformance, power management solution that
may be broadly applied to applications in the
industrial fields.
A common problem in such off-line applications is
the generation of a low voltage power supply for
the various control ICs.
Fig. 1: Typical application schematic of the TD220/22
Figure 1
.
Because of this, the TD220/221 includes a
"Two-Point Regulator” that enables control of a
switching charge pump connected.
The charge pump diodes are integrated within the
TD220/221, and a switch disables the charge
pump when the nominal voltage is reached.
The main advantage of the TD220/221 is that it
integrates, in a single SO8 package, 3 block
functions—voltage regulation, power supply and
power MOS driver—at a very reasonable price.
In typical applications, the TD220/221 manages
the following functions:
l
The MOSFET gate driver.
l
The microcontroller’s 3.3 V or 5 V supply.
l
The power supply voltage at 13 V.
October 2003
Revision B 1/5
AN1707 Introduction
Fig. 2: Description of the TD220/221
As shown in
Figure 1
, the TD220/221 internal
blocks are:
l
Source—Used in order to bias other blocks in
the circuit,
l
UVLO—Under Voltage Lock Out,
l
Vreg—Voltage Regulator at 3.3 V (for the
TD220) or at 5 V (for the TD221),
l
Driver—Provides the current in order to
drive an external MOS,
l
TPR—Two Point Regulator,
l
Clamp—Fixes the maximum Vcc at 22 V.
The UVLO block insures that Vcc is set such that
the TD220/221 functions correctly. Two boundary
voltages are internally fixed at 14.1 V (UVLOH)
and at 8.2 V (UVLOL). If the circuit is in the OFF
state, it will turn on when the UVLO voltage
reaches 14.1 V. This represents the minimum
value necessary to turn the circuit ON, and then
Fig. 3: TPR schematic: LDMOS Off
the Vcc power supply value stabilizes at 13 V.
When the circuit is in the ON state, maximum
UVLO voltage value that turns the circuit OFF is
8.2 V.
The role of the UVLO is both simple and
extremely important: it imposes the voltage range
for circuit ignition and blocking.
When the Vcc is at 13 V the Vreg b lock pr ovides a
precise output voltage at 3.3 V (for the TD220) or
at 5 V (for the TD221) with accuracy of ±3% at
25°C and for Iout = 10 mA. This Vcc is used to
supply power to the driver of an external power
MOS.
The Vcc voltage is so exact thanks to the TPR
block that allows it to maintain an accuracy of
±300 mV. This variation is measured using the
external capacitor C1 = 100 nF as shown in
Figure 3
and
Figure 4
.
VCC VCAP
C1
Threshol d Com pa rat or Hi gh = 13. 15V
Threshol d Com pa rat or Low = 12. 85 V
D1
D2
VSUP
VCC
LDMO S
13V
V
C2
Isup
t
2/5
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