Rainbow Electronics MAX847 - Manual (Page 8)

MAX847
1-Cell, Step-Up
Two-Way Pager System IC
8 _______________________________________________________________________________________
LBO
LBI
CH0
0.6V
CH0
RUN/
COAST
OV0–OV4
SERIAL
I/O
CH1
CH2 CP2
CP1
CP0
S1
7
DAC0–DAC7
RESET
CONTROL
V FEEDBACK
CHARGE
NICD
OR
BACKUP
REGULATOR
PWM
(PFM IN
COAST)
CHG/REG
+
–
CP LB
N
6
11
2 5 27
SDO SDI SCL
3 26
9
REF
0.6V
1 µ F
10 µ A
3.3V
1.0V
REG3
1 µ F
8
RSIN 10
17 18 19 16 15
20
21
14
DR1 DR2IN DR2 DRGND
N
1.8 Ω 1.8 Ω
REG2 ON
REG3 ON
N N
P
P
N
P
7
+
–
+
–
+
–
FROM
NICD
FROM
BATTERY
7-BIT
CH
DAC
5
5
REG2
REG1
R2IN
C OFS
0.1 µ F
OFS
NICD
R OFS
15k
10 µ F
10 µ F
OUT
SYNC
FILT
PGND
LX1
BATT
1-CELL
BATTERY IN
L1
22 µ H
22 µ F
47 µ F
+
–
A OUT
+
–
CP RS
CS
28
RUN
1.28V
REFERENCE
1.0V
+
–
A
R3
BACKUP
REGULATOR
CLAMP ON WHEN
OV4 = 1
3.3V
CLAMP
1mA/
15mA
CHARGE
P
+
–
A R2
+
–
A
R1
AGND
22
23
24
25
13
1nF 22nF
10k
12
4
1
x7
PLL
LBO
RSO
MAX847
Figure 1. Functional Diagram